Research ArticleMechanical Performance of Zr-Containing 354-Type Al-Si-Cu-MgCast Alloy Role of Additions and Heat Treatment

M H Abdelaziz 1 H W Doty2 S Valtierra3 and F H Samuel 1

1Departement des Sciences Appliquees Universite du Quebec a Chicoutimi Chicoutimi Canada2General Motors Materials Engineering 823 Joslyn Ave Pontiac MI 48340 USA3Nemak SA PO Box 100 Garza Garcia NL 66221 Mexico

Correspondence should be addressed to M H Abdelaziz mohamedabdelaziz1uqacca

Received 6 June 2018 Accepted 10 September 2018 Published 8 October 2018

Academic Editor Pavel Lejcek

Copyright copy 2018M H Abdelaziz et al is is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

In this article the volume fraction of intermetallic compounds in Zr-containing 354-type Al-Si-Cu-Mg alloys characteristics ofeutectic Si particles and tensile hardness and impact properties have been evaluated with varying Ni and Mn contents andcombination e results revealed that additions of Ni and Mn in different amounts and combinations increased the volumefraction of intermetallic compounds in the tailored alloys compared to the base alloy (cf 1221 for 4 Ni-containing alloy with25 for base alloy) producing a significant effect on the mechanical performance e proposed additions enhanced themechanical performance of the alloys namely the ambient- and elevated-temperature tensile properties hardness values andimpact properties For theMn-containing alloys the improvement in properties was attributed to the formation of sludge particlesin the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase that resisted crack propagatione precipitation ofNi-bearing phases such as Al9FeNi Al3CuNi and Al3Ni in the Ni-containing alloys improved the mechanical properties throughhindering cracks propagation Interestingly addition of 075wtMn to the base alloy proved to be competitive in strength valuesto the addition of 2 and 4wt Ni and better in terms of ductility valuese investigations showed that the variations in hardnessand impact values follow the same trend as variations in the percentage volume fraction of intermetallic compoundsie maximum property value is associated to the alloy with highest volume fraction of intermetallic compounds Furthermore theimpact properties showed higher dependency on Al2Cu phase particles rather than the eutectic Si particles

1 Introduction

In the automotive industry Al-Si-Cu-Mg 354-type alloys arewidely used in engine components owing to their excellentstrength and hardness values though at some sacrifice ofductility and corrosion resistance ese alloys are very re-sponsive to heat treatment in light of the presence of bothcopper and magnesium [1ndash4] e 354-type Al-Si-Cu-Mgalloy is considered as an optimum candidate for the manu-facture of multiple parts and components in the automotiveand aerospace industries including engine cooling fanscrankcases high-speed rotating parts structural aerospacecomponents timing gears rocker arms and many others[5ndash9] However during service these alloys are subjected toelevated temperatures higher than 190degC this high temper-ature instigates instability coarsening andor dissolution of

the major strengthening phases such as θprime(Al2Cu) βprime(Mg2Si)and Sprime(Al2CuMg) Consequently the resulting microstruc-tures are not favorable for maintaining the mechanical per-formance at elevated temperatures [10 11]

Many studies have been carried out in the past decadeon how to maintain the mechanical properties of alumi-num alloys at service temperatures that exceed 200degCAmong these the addition of small amounts of transitionmetals was found to be a promising approach to maintainthe mechanical properties of aluminum alloys at temper-atures of up to 300degC [712ndash16] e idea is based on theformation of secondary fine heat-resistant Al3M disper-soids where ldquoMrdquo is a transition element such as Zr Ni andMn [10 12] e selection process of the transition ele-ments to be added to Al-alloys is a key factor in achievingthe intended objective

HindawiAdvances in Materials Science and EngineeringVolume 2018 Article ID 5715819 17 pageshttpsdoiorg10115520185715819

Knipling et al [17] have introduced four criteria that haveto be satisfied in the selection process of alloying elements inorder to obtain castable precipitation-strengthened aluminumalloys with both high stability and strength at elevated tem-peratures ese criteria state that the alloying element must

(i) produce a suitable strengthening phase (precipitates)(ii) have a low solid-solubility in aluminum at the aging

temperatures involved(iii) have a low diffusivity in aluminum(iv) preserve the alloy capability to be conventionally

solidified

Zirconium has one of the lowest diffusion rates inaluminum in comparison to other transition elements [18]Addition of Zr in the range of 01 to 03 wt to aluminum-based alloys leads to the formation of fine metastable L12-structured Al3Zr precipitates that have a very low latticeparameter mismatch with the Al matrix [19ndash21]ese Al3Zrprecipitates are noticeably stable and resist coarseningduring heating thus the addition of Zr satisfies the fourcriteria proposed by Knipling et al [17]

Similar to the outstanding behavior of Ni-based alloys athigh homologous temperature owing to the existence of theNi3Al phase researchers anticipated that a similar trend inbehavior could be achieved in Al-based alloys by developingthe Al3Ni phase which is analogous to the Ni3Al (cprime) phaseupon the addition of Ni to Al alloys is trialuminide phase(Al3Ni) is thought to enhance the mechanical performance atelevated temperatures [12] On the other hand the addition ofMn to Fe-containing aluminum alloys is a practice commonlyused to neutralize the negative effects of Fe Manganese canmodify the morphology and the type of Fe-intermetallicphases which usually exist in aluminum cast alloys [22ndash24]e addition ofMnwill promote the formation of the lessharmful α-iron AlFeMnSi phase with Chinese script-likemorphology which will in turn improve the overall me-chanical properties of Al alloys [6 25 26]

Based on the above arguments Zr was added to the 354alloy used in this study to form the base or reference alloyand other elements (Ni and Mn) were subsequently addedindividually or in combination to study their mutual effectwith Zr on the mechanical properties of 354 alloy at roomand elevated temperatures and to achieve an appropriatemodified chemistry of 354-type (Al-Si-Cu-Mg) alloys whichcould enhance the overall mechanical performance of thiscategory of alloys as well as to resist the softening at elevatedtemperature during service

2 Experimental Procedure

ealloys prepared for this work have been tailored from 354-type Al-Si-Cu-Mg alloy through adding Zr as a commonalloying element along with the addition to Ni andor Mn indifferent amounts and combinations Alloy codes and re-spective addition are as follows

(1) Alloy M1S 354 + 03 wt Zr (base alloy)(2) Alloy M2S Alloy M1S+ 2wt Ni

(3) Alloy M3S Alloy M1S + 075wt Mn(4) Alloy M4S Alloy M1S + 4wt Ni(5) Alloy M5S alloy M1S + 2wt Ni + 075wt Mn

e base alloy was selected based on its improved me-chanical performance that was previously reported in thesame research group [7 27] e chemical composition ofthe alloys under investigation is listed in Table 1

e 354 alloy ingots were cut dried andmelted in a 70-kgcapacity SiC crucible using an electric resistance furnace emelt was kept at a temperature of 800plusmn 5degC e addition ofmaster alloys was carried out instantly before starting thedegassing process in order to ensure homogeneous mixing ofadditives during degassing After successful degassing themelt was carefully skimmed to remove the oxide layers fromthe melt surfaceemelt was then poured into the preheatedpermanent mold of interest using a preheated pouring cupwith a ceramic foam filter (15 ppi) in order to avoid entranceof inclusions and oxide films into the mold Each permanentmold employed was preheated at 450degC in order to remove alltraces of moisture from the mold

An ASTM B-108 type permanent mold was used toprepare castings from which the standard tensile test barswere obtained with a gauge diameter of 127mm Forpreparing unnotched impact test bars star-like mold wasused to produce the impact test bars according to the ASTME23 standard e impact test bars have a square cross-sectional area of 10times10mm2 and a length of 55mm For thehardness test bars L-shaped mold was used to produce anL-shaped casting After cutting off the feeding head eachcasting was cut to produce three rectangular bars whichwere subsequently machined to the final geometry(35times 30times 80mm) of the hardness test bars

For the alloys investigated (ie M1S through M5S) thetest bars of the five alloys were heat treated according to theprocedures and parameters listed in Table 2

Tensile testing at ambient temperature was carried outusing an MTS servo-hydraulic mechanical testing machine ata strain rate of 4times10minus4 sminus1 till the point of fracture Five testbars for each alloycondition were tested and the averagevalues of ultimate tensile strength (UTS) 02 offset yieldstrength (YS) and percentage elongation to fracture ( El)were reported An Instron Universal mechanical testingmachine was used to carry out the tensile testing at elevatedtemperature (250degC) using the strain rate of 4times10minus4 sminus1 etesting was carried out at 250degC after holding the test bar for15min at the testing temperature in order to homogenize thetemperature of the sample to 250degC throughout e testsample was kept unmounted from one side inside the heatingchamber during the holding process to avoid compressivestresses that might arise from the expansion of the bar andthen it was mounted from the other side and kept at thetesting temperature for another 15min Five test bars wereused for each alloy compositioncondition studied and theaverage values of UTS YS and El were reported

Hardness measurements were carried out on the pre-pared hardness test bar samples A Rockwell hardness testerand F scale were employed using a 116-inch steel ball

2 Advances in Materials Science and Engineering

indenter and a load of 60 kgf Ten measurements were madeper sample and the average value was reported as theRockwell hardness value of that alloy samplecondition

A computer-aided instrumented SATEC SI-1 UniversalImpact Testing Machine was used to carry out the impacttesting e instrument and the attached data acquisitionsystem provide the total absorbed energy (Et) of the sampleduring the impact test Five samples for each alloyconditionwere tested and the average value of the total energy ob-tained was reported

Samples for metallographic observation were sectionedfrom the test bars mounted and polished using standardpolishing procedures e polished samples were examinedusing an Olympus PMG3 optical microscope connected toa Clemex Vision PE image-analysis system A scanningelectron microscope (SEM JEOL JSM-6480LV) equippedwith energy dispersive X-ray spectrometer (EDS) was usedto investigate the intermetallic compounds and the fracturesurfaces

3 Results and Discussion

31 Microstructural Characterization

311 Intermetallic Compounds e volume fraction () ofintermetallic compounds observed in as-cast and as-quenched tensile bars is presented in Table 3 Figure 1compares backscattered electron (BSE) images of all alloysin the as-cast (left) and as-quenched (right) conditions ebackscattered images shown to the right in Figure 1 dem-onstrate clearly the reduction in the volume fraction of theintermetallic compounds in the as-quenched samples

For the as-cast condition it is obvious that the additionof Ni and Mn in different amounts and combinations(ie alloys M2S through M5S) significantly increases thevolume fraction of existing phases compared to the basealloy (cf 25 for alloy M1S and 1221 for alloy M4S)Alloy M4S which contains 4wt Ni shows an excessiveincrease in volume fraction in comparison to alloys M2SM3S andM5Sis substantial increase may be attributed tothe formation of Ni-containing phases such as Al3CuNiAl9FeNi and Al3Ni in addition to the phases commonlyobserved in other alloys such as the Q-phase Al2Cu Mg2Siand Fe-containing phases Other Ni-containing alloysie M2S andM5S contain almost the same phases howeverthe structure of alloy M4S uniquely comprises the eutecticAl-Al3Ni structure as shown in Figures 1(g) and 1(h) iseutectic structure is believed to increase the overall volumefraction of intermetallic compounds in alloy M4S

e addition of 075wt Mn to the base alloy ie alloyM3S doubles the volume fraction in the as-cast conditionand may be ascribed to the formation of α-Al15(FeMn)3Si2phase in script-like and sludge morphologies [28] In ad-dition the presence of the α-Al15(FeMn)3Si2 phase that doesnot dissolve with solution heat treatment would explain thenearly three times higher volume fraction observed in the as-quenched condition for alloy M3S compared to the basealloy M1S similar to the observations of Elgallad [19]

As may be seen from Table 3 and Figure 1 applyingsolution treatment reduces the volume fraction () of in-termetallic compounds owing to the dissolution of the Al2Cuphase and the partial dissolution of other phases such as Q-Al5Mg8Cu2Si6 Mg2Si Al3CuNi β-Al5FeSi π-Al8Mg3FeSi6and Al9FeNi [7]

312 Characteristics of Eutectic Silicon Particles e alloysstudied M1S through M5S were modified by adding200 ppm of strontium (Sr) erefore it is expected that theeutectic silicon particles will be modified to a large extent inthe as-cast condition in all alloys e morphology of eu-tectic silicon particles in the as-cast and as-quenched alloysamples is displayed in the optical micrographs shown inFigure 2 while the corresponding average Si particlecharacteristics are listed in Table 4 the average values wereobtained from measurements of 20 fields per alloysamplecondition

e optical micrographs shown in Figure 2 for the as-cast alloy samples on the left reveal that the majority ofsilicon particles are fully modified nevertheless partiallymodified silicon particles may still be observed in these

Table 3 Volume fractions () of undissolved intermetalliccompounds in the matrix of as-cast and as-quenched alloys

Volume fraction()

Alloy codeM1S M2S M3S M4S M5S

As-cast Average 251 617 434 1221 879SD 041 056 036 077 079

SHT Average 111 554 364 960 768SD 028 061 016 065 052

Table 1 Chemical composition of the alloys investigated in thisstudy

Chemical analysis (wt)

Alloycodes

ElementsSi Cu Mg Fe Ti Zr Ni Mn Sr Al

M1S 85 176 055 012 02 032 lt01 001 0022 BalM2S 84 17 060 014 021 033 19 001 0018 BalM3S 86 18 055 011 020 033 lt01 075 0020 BalM4S 86 18 067 012 022 029 4 001 0019 BalM5S 86 18 060 015 020 029 19 076 0018 Bal

Table 2 Heat treatment procedures and parameters applied toalloys studied

Heat treatment procedures and parametersHeattreatment

Solutiontreatment Quenching Aging

SHTlowast 495degC for 5 h Warm water(60degC) NA

T5 temper NA NA 180degC for 8 h

T6 temper 495degC for 5 h Warm water(60degC) 180degC for 8 h

SHT solution heat treatment

Advances in Materials Science and Engineering 3

(a) (b)

(c) (d)

(e) (f )

(g) (h)

Figure 1 Continued

4 Advances in Materials Science and Engineering

(i) (j)

Figure 1 Backscattered electron images for as-cast (left) and solution heat-treated (right) conditions of the alloys studied (a b) M1S (basealloy) (c d) M2S (2wt Ni) (e f ) M3S (075wt Mn) (g h) M4S (4wt Ni) and (i j) M5S (2wt Ni + 075 wt Mn)

(a) (b)

(c) (d)

(e) (f )

Figure 2 Continued

Advances in Materials Science and Engineering 5

micrographs to a certain extent e existence of thesepartially modified silicon particles could be a result of thehigh Mg content sim06 wt of the alloys It has been re-ported by Joenoes and Gruzleski [29] and Dunn and Dickert[30] that the presence of Mg and copper can change themicrostructure from a fully modified structure into a par-tially modified one due to the formation ofMg2Sr(Si Al) andAl-Cu-Sr phases which will result in reducing the amount ofavailable strontium (Sr) to achieve the required degree ofmodification of the eutectic silicon particles In the present

case however since the contents of Sr Cu and Mg are keptconstant in the alloys investigated other explanations aremandatory to explain the variations in the modification levelof the eutectic Si particles in these alloys

As per the micrographs shown in Figures 2(e) and 2(g)alloys M3S (354 + 002wt Sr + 03 wt Zr + 075wtMn) and M4S (354 + 002wt Sr + 03 wt Zr + 4wt Ni)appear to contain less amounts of partially modified eutecticsilicon is observation can be ascribed to the existingphases in the microstructure of the two alloys which may

(g) (h)

(i) (j)

Figure 2 Optical micrographs at 500X showing the morphology of the eutectic silicon in the alloys studied (left) as-cast conditions and(right) solution heat-treated conditions (a) as-cast alloy M1S (b) SHTalloy M1S (c) as-cast alloy M2S (d) SHTalloy M2S (e) as-cast alloyM3S (f ) SHT alloy M3S (g) as-cast alloy M4S (h) SHT alloy M4S (i) as-cast alloy M5S and (j) SHT alloy M5S

Table 4 Characteristics of eutectic silicon particles in as-cast and solution heat-treated conditions of the alloys studied

Alloy code and conditionParticle area

(μm2)Particle length

(μm) Aspect ratio Roundness () Sphericity ()

Av SD Av SD Av SD Av SD Av SDM1S-AC 285 439 267 248 196 133 049 021 075 028M1S-SHT 371 471 260 210 171 149 058 019 085 021M2S-AC 353 760 283 329 196 244 050 023 074 030M2S-SHT 567 808 327 295 179 127 056 020 081 023M3S-AC 192 310 214 222 192 243 051 022 077 028M3S-SHT 535 604 312 232 169 292 061 017 086 019M4S-AC 311 661 265 330 202 358 050 025 073 032M4S-SHT 399 553 268 243 186 265 056 022 082 023M5S-AC 387 688 312 343 212 627 048 022 070 030M5S-SHT 570 744 352 320 195 360 054 020 078 025

6 Advances in Materials Science and Engineering

contribute to variations in the free content of silicon andorstrontium Such variations may lead to a more efficientmodification in the case of a lower SiSr ratio and vice versa

On one hand a high amount of the copper in alloy M4S(containing 4 Ni) is consumed in forming Al3NiCu phase[11] and thus the possibility of forming the Al-Cu-Sr phasereported by Joenoes and Gruzleski [29] will be reducedConsequently more Sr will not be consumed to form the Al-Cu-Sr phase and thus better modification would be ex-pected for Ni-containing alloys particularly those withhigher Ni-content as in alloy M4S On the other hand theaddition of 075 wt Mn in alloy M3S changes some of theβ-Al5FeSi iron phase into Chinese script-like α-Al15(FeMn)3Si2 phase and sludge particles e mutual existence ofthe two Fe-based phases ie β-Al5FeSi and α-Al15(FeMn)3Si2 will lower the silicon content (ie reduce the Siphase) in alloy M3S to an extent which will allow a bettermodification level compared to that attained for the rest ofthe alloys studied as depicted in Figure 2(e)

ermal modification is yet another effective way toalter the morphology of eutectic silicon particles It isevident from the micrographs shown in Figure 2 on theright that the solution treatment changes the fibrousinterconnected eutectic silicon particles detected in the as-cast condition into globular particles with rounded edgese evolution of the morphology of the eutectic siliconparticles from fibrous to globular in these alloys is a directresult to the combined effect of solution-heat treatment andstrontium modification as previously stated by Chen et al[31] and Yuying et al [32]

It is evident from the data presented in Table 4 that theaverage Si particle area increases after solution treatment at495degC for 5 hours for all the alloys Additionally the sol-utionizing treatment produces a noticeable improvement inthe spheroidization of the Si particles concomitant withenhancements in the roundness values as can be seenqualitatively from the micrographs shown in Figure 2 eincrease in sphericity and roundness values would producea corresponding decrease in the aspect ratio as seen inTable 4

32 Mechanical Performance

321 Ambient-Temperature Tensile Testing In the presentstudy the sole addition of sim03 wt Zr to the 354-type Al-Si-Cu-Mg cast alloy (ie the base alloy M1S) in the as-castcondition enhances the ambient-temperature strengthvalues of the Zr-free 354 alloy (alloy A) used in previousinvestigations in the same group by Hernandez-Sandoval[16] by sim26MPa (UTS) and 40MPa (YS) respectivelyese enhancements in the strength values are accompaniedby a limited reduction in the alloy ductility (sim0054) Forthe solution heat-treated condition on the other hand theUTS and ductility values of the base alloy M1S remainvirtually constant at sim300MPa and sim63 respectivelywhile the yield strength increases by sim33MPa compared toalloy A in the work of Hernandez-Sandoval [16] e im-proved strength values of Zr-containing Al-Si-Cu-Mg alloy

emphasize the role of Zr addition in enhancing the ambient-temperature tensile properties

Figure 3 shows the ambient-temperature tensile prop-erties obtained for the alloys under investigation In the as-cast condition the base alloy M1S (354 + 03 wt Zr) showsthe lowest UTS and YS values As-cast strength values of theother alloys ie M2S through M5S show enhancements of14ndash25 and 16ndash26 in UTS and YS respectively comparedto the base alloy (M1S) However the ductility values ofalloys M2S through M5S show inconsistent variations withrespect to the ductility of the base alloy M1S these variationscomprise enhancements in case of alloy M3S deteriorationsin the case of alloys M4S and M5S and almost unchangedductility value in the case of alloy M2S

e probable explanations for the enhanced strengthvalues of alloy M3S are the formation of favorable phaseswhich are advantageous to the strength values and thehighly refined as-cast Si particles (Table 4) as a result to theaddition of 075 wt Mn to the base alloy (M1S) It is wellestablished that the addition of Mn neutralizes to someextent the deleterious effect of iron impurities by trans-forming the detrimental needle-like β-Al5FeSi phase into theless harmful α-Al15(Fe Mn)3Si2 phase which appears ineither script-like form or as blocky sludge particles or bothWhile there is no doubt about the positive effect of thescript-like α-phase on strength and ductility values there ismuch debate however on the effect of the sludge particleson the tensile properties either they are harmful as regularlybelieved [28 33 34] or favorable to the tensile properties[7 35 36] Garza-Elizondo [7] has reported that the presenceof these hard particles in the soft α-Al matrix may contributein enhancing the tensile properties through the developmentof more uniformly distributed stresses within the matrix

For the Ni-containing alloys enhancements in thestrength values can be correlated to the formation of Ni-containing intermetallic compounds such as Al9FeNiAl3CuNi and Al3Ni which can hinder the propagation ofcracks similar findings are reported in previous studies[11 16] Increasing the Ni content from 2wt to 4wtinversely affects the tensile properties at room temperatureIt is believed that the precipitation of higher volume frac-tions of the acicular Al9FeNi and Al3CuNi phases in the as-cast alloy M4S (4wt Ni) is responsible for the de-terioration of the tensile properties at room temperature

Apparently from Figure 3 the base alloy M1S proves tobe very responsive to solution heat treatment because itshows an increase of 40MPa and 8MPa in the as-cast UTSand YS values respectively after solutionizing at 495degC for 5hours In addition the ductility of the solutionizedM1S alloyalso shows an increase of sim5 over the ductility valueobtained for the as-cast condition On the other hand theother alloys ie M2S through M5S show small improve-ments in the range of 2ndash10MPa for UTS values anda noticeable reduction in YS values (18ndash36MPa) comparedto their strength values in the as-cast conditione ductilityvalues of alloys M2S through M5S increase after solutiontreatment e enhanced ductility values after solution heattreatment in particular are related to the changes in theeutectic silicon morphology Coarse acicular silicon particles

Advances in Materials Science and Engineering 7

serve as crack initiators which is the case in the as-castcondition whereas more spherical Si particles with roundededges and decreased aspect ratios are obtained in the so-lution heat-treated case

Figures 3(a) and 3(b) show that the strength values of thebase alloy M1S are 289MPa (UTS)259MPa (YS) and342MPa (UTS)325MPa (YS) in the T5- and T6-treatedconditions respectively Alloys M2S and M3S exhibit thehighest strength among the alloys studied with values of300MPa (UTS)277MPa (YS) and 315MPa (UTS)279MPa(YS) respectively in the T5-treated condition and 362MPa(UTS)352MPa (YS) and 357MPa (UTS)355MPa (YS) inthe T6-treated condition respectively e strength values(UTS and YS) of alloys M1S M2S (M1S+ 2wt Ni) andM3S (M1S+075wtMn) show distinct enhancements afterapplying the T6 treatment in comparison to the as-cast andas-solutionized conditions In contrast alloys M4S (M1S+4wt Ni) and M5S (M1S+2wt Ni+075wt Mn)exhibit a very limited enhancement in UTS (sim15MPa) after T6heat treatment with reference to their strength in the as-castand as-quenched conditions Additionally from Figure 3(c) itcan be seen that the ductility values reduce considerably afterT6 treatment when compared to the as-cast ductility values ofthe respective alloys Ductility values of the alloys studied arelimited in general due to the high silicon content sim9wt andthe presence of both Mg and Cu [30]

e enhanced strength values of alloy M2S particularlyfor the T6-treated condition can be attributed to thepresence of Ni-containing phases such as Al3Ni Al9FeNiand Al3CuNi in addition to the ne precipitates formedafter applying T6 treatment [37 38] With respect to alloyM3S the improved strength values following T5- and T6-heat treatments can be ascribed to (i) the presence ofα-Al15(Fe Mn)3Si2 in the form of blocky hard particles (ii)the precipitated strengthening Cu- and Mg-containingdispersoids and (iii) the probable formation of Al6Mnne dispersoids in the presence of a high Mn content of075 wt [39 40] e presence of these Mn dispersoidssignicantly improves the yield and ultimate strength valueswithout sacricing the ductility [39 41 42]

e presence of a high nickel content in T6-treated alloyM4S (4wt) results in deteriorating the ambient-temperature tensile properties as can be inferred fromFigure 3 similar observations have been noted by otherauthors [71043ndash46] is deterioration in the strengthvalues is a direct result of the high content of Ni which inturn will consume some of the available copper in the alloyto form the detected Al3CuNi phase As a result this willreduce the amount of copper available for strengtheningthrough precipitation hardening during heat treatment [10]Furthermore the precipitation of Al9FeNi and Al3CuNiphases in high volume fractions (Table 3) would facilitate

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(a)

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(b)

01234567

AC SHT T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

M1SM2SM3S

M4SM5S

(c)

Figure 3 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in as-cast solution heat-treated (SHT) and T5- andT6-treated conditions obtained at ambient temperature

8 Advances in Materials Science and Engineering

cracking since they would act as stress raisers causinginstability in the flow strain and hence the ductility of thisalloy will reduce accordingly

In general the room-temperature tensile properties inthe T6 heat-treated conditions are better than those obtainedwith the T5 treatment for the alloys studied e use ofpermanent mold casting which is the technique used forproducing the test bars would preserve copper and mag-nesium in considerable amounts in solid solution due to thehigh solidification rate us by applying artificial agingdirectly after solidification (ie T5 temper) large pro-portions of the dissolved Cu andMg in the solid solution willform strengthening dispersoids e T6 heat treatment onthe other hand involves solutionizing the as-cast structure ata sufficiently high temperature in order to dissolve higheramounts of Cu and Mg in solid solution in order to forma supersaturated solid solution upon quenching and toachieve further modification of the eutectic Si particlesus the artificial aging in the case of T6 treatment willprecipitate fine strengthening particles in larger proportionsthan in the case of T5 treatment which will enhance the alloystrength to a greater extent however at the expense ofductility

For the alloys studied the ambient-temperature tensiletesting data are listed in Table 5 along with the quality indexvalues which were calculated using Equations (1) and (2)according to the models developed by Drouzy et al [47] andCaceres [48] respectively

Q SUTS + dlog ef 1113857 (1)

Qc K (qn)n expminusqn + 04 log(100qn)1113858 1113859 (2)

where Q and Qc (MPa) are the quality indices according toDrouzy and Caceres models SUTS refers to the ultimatetensile strength (MPa) ef refers to the percentage elongationto fracture d is a material constant equal to 150MPaK is thestrength coefficient (MPa) relative quality index (q) and n isthe strain-hardening exponent

Figure 4 shows the quality chart for the alloys studiedbased on Drouzy [47] model and depicts variations in thequality index values based on the chemical composition andthe applied heat treatment Equations (1) and (3) were usedto develop the ldquoiso-Qrdquo and ldquoiso-YSrdquo lines in the chart

Sp(ys) aSUTS minus blog ef 1113857 + C (3)

where coefficients a b and c were quantified as 1 60MPaand minus13MPa respectively

e quality index values Q and Qc listed in Table 5 showthe same trend in variations however with different valuese difference between Q and Qc increases in the T5 and T6heat-treated conditions which can be accredited to the factthat the alloy quality is affected by the net amount by whichthe increase in strength is balanced by the reduction inductility As can be seen from Table 5 and Figure 4 the bestquality values for the alloys are obtained after solution heattreatment attributed to the microstructural changes thattake place during the solution treatment including thedissolution of strengthening elements the homogenization

of the segregated as-cast structure and the spheroidizationof the eutectic silicon particles ese changes will signifi-cantly enhance the alloy ductility in addition to a limitedenhancement in UTS values Consequently the quality in-dex values of the as-quenched (or solution heat-treated)alloys are remarkably higher than those in the as-castcondition

While the T6 heat treatment improves the UTS valuesconsiderably in comparison to the UTS values obtainedafter solution treatment it does so at the expense of theductility is trade-off between UTS and ductility valueswill certainly affect the quality index values and not nec-essarily in a positive way Likewise a similar behavior isnoted for the T5-treated alloys as well as can be inferredfrom Figure 4

It is evident that the superior ductility of the base alloyM1S is the main reason for the improved quality indices ofthis alloy in the majority of the conditions studied On theother hand the mutual enhancement in the strength andductility values of alloys M2S and M3S compared to those ofalloys M4S and M5S is responsible for the higher qualityindices of the former compared to those of the latter

e addition of Mn in alloy M3S results in transformingthe needles of the β-iron phase into the less detrimentalα-iron phase this favorable morphological change is be-lieved to improve the ductility and strength values of alloyM3S Whereas the structure of alloy M2S contains Ni-bearing phases with acicular morphologies and β-ironneedles that negatively affect the mechanical propertiesAccordingly the quality index values of alloy M3S are higherthan those of the 2wt Ni-containing alloy M2S in the as-cast SHT and T5 conditions In contrast the quality indexvalues of the T6-treated alloysM2S andM3S show a reversedbehavior according to the marginal variations in their tensileproperties and hence the quality index values

From Table 5 it is observable that the quality indexvalues calculated using Drouzyrsquos approach are higher thanthose obtained by the model developed by Caceres for alltreatment conditions per each alloy except for solution-treated conditions is can be attributed to the improvedductility of as-quenched conditions that will allow moreaccurate determination of the material parameters (K andn) us it would be advisable to calculate the quality indexvalues of solution-treated conditions using Caceresrsquo modelespecially for materials with low ductility at roomtemperature

322 Elevated-Temperature Tensile Testing Figure 5 revealsthe elevated-temperature tensile properties obtained at250degC for the alloys studied By tensile testing at 250degC allthe investigated alloys endure some softening owing to thepossible coarsening of the strengthening precipitates thatexist during tensile testing at room temperature (Figure 3)Figures 5(a) and 5(b) demonstrate that additions of Ni andMn in different amounts and combinations to the base alloyie alloys M2S through M5S slightly improve the strengthvalues of the base alloy in the range of 5ndash15MPa for both as-cast and T5-treated conditions e tight enhancement in

Advances in Materials Science and Engineering 9

strength values of the T5-treated conditions can be ascribed tothe limited variations in themicrostructural features of as-caststructures as well as to the low proportion of strengtheningprecipitates in the structure of T5-treated alloys

In regard to the ductility values in the as-cast conditionFigure 5(c) reveals that the highest ductility value is observedto be associated with the base alloy M1S with a value of

sim36 followed by the ductility of the Mn-containing alloysM3S andM5S and ending up with the lowest ductility valuesfor alloys M2S and M4S containing 2 and 4wt Ni re-spectively e higher ductility values of the as-cast Mn-containing alloys M3S andM5S can be attributed to the well-refined Si particles Table 4 and the transformation ofa considerable amount of β-Al5FeSi needles which may act

Table 5 Variation in average UTS YS El Qc and Q values of the alloys studied in as-cast SHT and T5- and T6-treated conditionsobtained at ambient temperature

Alloy Condition UTS(MPa)

YS(MPa)

Totalstrain ()

Plasticstrain () E (GPa) n K q Qc

(Equation (2))Q

(Equation (1))Difference

(QminusQc) (MPa)

M1S

As-cast 26086 19439 158 116 6266 018 58056 007 27788 29050 1262SHT 30034 20251 622 574 6250 017 57926 034 51236 41943 minus9293T5 28950 25875 094 048 6306 013 59169 004 21706 28543 6838T6 34195 32499 11075 056 6245 010 57691 006 28153 34860 6707

M2S

As-cast 32035 23585 163 116 6758 019 76378 006 34214 35219 1005SHT 32774 21261 320 270 6623 017 75932 016 53109 40343 minus12766T5 29997 27719 080 034 6564 015 70196 002 16710 28522 11812T6 36233 35157 080 024 6471 011 70779 002 19604 34816 15212

M3S

As-cast 32578 24572 176 126 6473 015 64889 008 35471 36255 784SHT 33475 20943 381 330 6447 012 64647 027 54926 42197 minus12729T5 31458 27939 098 049 6414 013 63449 004 23821 31310 7489T6 35701 35514 075 020 6432 008 62421 002 19202 33850 14648

M4S

As-cast 30440 22461 133 087 6610 020 83677 004 29364 32287 2923SHT 31232 20709 222 175 6656 018 82135 010 46959 36427 minus10532T5 27644 25414 071 031 6843 020 85707 002 9928 25451 15524T6 31598 31598 05705 011 6710 010 63474 001 7752 27941 20189

M5S

As-cast 29707 22659 127 083 6691 020 79201 004 27391 31280 3889SHT 29979 20664 199 154 6735 017 78035 009 43714 34462 minus9252T5 28461 27700 066 022 6474 015 72211 001 9720 25745 16025T6 31404 31404 056 011 6789 011 67764 001 4543 27632 23089

1

23

12

3

1 2

3

12

3

1 23

250

300

350

400

05 5

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

Drouzy quality index chart room temperature

M1SM2SM3S

M4SM5S

4 4

44

YS = 350 MPa

Q = 500 MPaQ = 450 MPa

Q = 350 MPa

Q = 250 MPa

Q = 300 MPa

Q = 400 MPa

YS = 250 MPa

4

1 as-cast2 SHT3 T54 T6

Figure 4 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast SHT and T5- and T6-treated conditions obtained at ambient temperature

10 Advances in Materials Science and Engineering

as crack initiators into the less detrimental α-Al15(MnFe)3Si2 phase with script-like andor sludge morphologies

e addition of Ni on the other hand lowers theductility values even for alloy M5S that contains 075wtMn when compared to alloy M3S which is Ni-free ereduction in ductility values of the as-cast Ni-containingalloys can be directly correlated to the presence of acicularNi-bearing phases with sharp edges such as Al3Ni Al9FeNiand Al3CuNi phases Variation in chemical compositionshas a limited eiexclect on the ductility values obtained at 250degCfor the T5-treated alloys since the maximum absolutediiexclerence in the ductility values of alloys M2S through M5Sis found to be sim044 Application of T5 and T6 heattreatments reduces the ductility observed in the as-castcondition e ductility values in the T6-treated conditionare generally lower than those obtained with T5 treatmentconditions

e application of the T6 heat treatment enhances thestrength values of as-cast conditions regardless the alloycomposition as shown in Figures 5(a) and 5(b) e en-hanced strength values of alloy M4S after T6 heat treatmentmay be attributed to the presence of δ-Al3CuNi and eutecticAl-Al3Ni phases that prove to contribute eiexclectively to theelevated-temperature strength of alloy M4S in spite ofa considerable amount of Cu that is consumed in formingthe δ-Al3CuNi phase which will certainly aiexclect the amount

of ne Al2Cu dispersoids formed which is consistent withthe ndings reported in references [38 49]

Interestingly alloys M3S (354 + 075wt Mn) and M4S(354 + 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the diiexclerent conditions ex-amined Moreover alloy M3S is considered to be morefavorable between the two since it exhibits higher ductilitythan that of the Ni-containing alloy M4S ese two alloysexhibit the best strength values (UTS and YS) in the T6-treated conditions among the investigated alloys whereasthe strength values of the other three alloys ie alloys M1SM2S and M5S are close to each other and lower than thestrength values obtained for alloys M3S and M4S bysim36MPa is observation would emphasize the advanta-geous role of adding Mn instead of Ni to enhance theelevated-temperature tensile properties along with its eco-nomic impact

Generally the closeness of the elevated-temperaturestrength values of the alloys studied can be credited tothe presence of 03 wt Zr in each alloy whereby theformation of the ne metastable L12-Al3Zr particles is ex-pected in the microstructures of all the alloys which in turnwill improve the alloy strength in a common manner

For elevated-temperature tensile properties the conceptof the quality index will be discussed according to theconcept of Drouzy et al [47] (Q) Table 6 demonstrates the

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditionsM1SM2SM3S

M4SM5S

(a)

M1SM2SM3S

M4SM5S

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditions

(b)

M1SM2SM3S

M4SM5S

005

115

225

335

445

AC T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

(c)

Figure 5 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in the as-cast solution heat-treated (SHT) and T5-and T6-treated conditions obtained at 250degC

Advances in Materials Science and Engineering 11

elevated-temperature tensile data along with the quality indexvalues (Q) of the alloys studied calculated using Equation (1)Figure 6 shows the quality chart obtained based on the cal-culations of Drouzy et al [47] As may be seen the qualityindex values obtained at 250degC do not show wide variation invalues as was observed in the case of the ambient-temperature data is limited variation can be understoodin light of the balanced variation in UTS and ductility valuesobtained at the elevated temperature of 250degC For examplethe base alloyM1S in the as-cast condition exhibits the highestductility value of 367 and a UTS value of 16995MPa whilethe lowest ductility is experienced by alloy M4S for the T6-treated condition with a value of 106 along with a UTSvalue of 25358MPa By calculating the quality indices of thesetwo conditions they revealQ values of 26395 and 25735MPafor as-cast M1S and T6-treated M4S respectively ose twoextreme conditions show that despite the considerable vari-ation in the UTS values on the one hand and ductility valueson the other for these two conditions the quality indices inboth cases remain almost unchanged due to the balancedtrade-off between the UTS and ductility values e relativelylowUTS and ductility values obtained at elevated temperature(250degC) for the T5-treated condition result in the T5-treatedalloys exhibiting minimum Q values among the conditionsstudied

Another interesting observation is that the quality indexvalues for alloys M2S and M3S in the T6-treated conditionare found to be the maximum for the alloys and conditionsstudied is observation highlights the enhanced charac-teristics of alloy M3S which contains 075wt Mn andemphasizes the positive influence of the high Mn-additionon the elevated-temperature tensile properties which arefound to be more or less comparable to those obtained withthe addition of 2 and 4wt Ni to the same base alloy

e favorable role of the blocky α-Al15(Fe Mn)3Si2phase termed as sludge particles in improving the tensileproperties of alloy M3S at 25degC and 250degC can be witnessed

from the fractograph of alloy M3S after testing at 250degCpresented in Figure 7 e sludge particles appear to retardthe propagation of the cracks developed in the other phaseswhich will subsequently enhance the mechanical propertiesof the respective alloy Yet another interesting observationmade from this figure is that while many of the intermetallicphase particles appear cracked as indicated by the solidarrows the sludge particles however are crack-freeWhereas the multiple cracked Ni-rich phases exist on thefracture surface of alloy M2S after testing at 250degC are be-lieved to contribute to the crack initiation process and hencedeteriorate the tensile properties of this alloy as witnessed inFigure 8

323 Hardness Values Figure 9 illustrates the variation inthe hardness values of the alloys as a function of the appliedheat treatment At first glance one can observe from Figure 9that the hardness values of different alloys show insignificantvariations for the same conditions For each alloy the peak-aged condition exhibits the highest hardness value among allconditions Also the tailored alloys ie M2S through M5Sshow better hardness values than those obtained for the basealloy in all the conditions studied

Variations in hardness values of the alloys in the as-castcondition can be attributed to the additions of Ni andor Mnmade to the base alloy M1S It was seen that additions of Niandor Mn in various amounts increased the volume frac-tions of intermetallic compounds considerably as listed inTable 3 e variations in hardness values follow the sametrend as variations in the percentage volume fraction ofintermetallic compounds us the base alloy M1S exhibitsthe lowest hardness value in the as-cast condition having thelowest volume fraction according to Table 3 and the highesthardness value of the same condition is associated with alloyM4S that has the highest volume fraction of intermetalliccompounds is observation highlights the effective role ofintermetallic compounds in enhancing the hardness values[19 50]

e dissolution of the strengthening elements over thecourse of the solution treatment reduces the hardness valuesin spite of the expected improved homogeneity in com-position and evolution of the eutectic silicon morphologyfollowing solution treatment is behavior emphasizes thecrucial role of intermetallic phases in influencing the me-chanical performance of alloys It is established that thehardness value of a specific alloy corresponds to the com-bination of the tensile yield strength and work-hardeningrate of the alloy [50 51] e order of the alloys studiedaccording to the hardness value in the as-quenched con-dition matches to a large extent their order with respect totheir yield strength in the same as-quenched condition(Figure 3)

Direct artificial aging following casting of test barsie T5-temper treatment introduces slight improvements inthe hardness values with respect to those obtained for the as-cast condition is can be attributed to the limited changesin the microstructure of the as-cast alloysbars followingdirect artificial aging without solution treatment e slight

Table 6 Variation in average UTS YS El and Q values of thealloys studied in as-cast and T5- and T6-treated conditions ob-tained at 250degC

Alloy Condition UTS(MPa)

YS(MPa) El Q (Equation (1))

M1SAs-cast 16995 15756 367 25465T5 17207 16151 202 21791T6 21765 21365 192 26014

M2SAs-cast 18632 17284 225 23915T5 19625 17885 160 22671T6 22372 22233 215 27365

M3SAs-cast 17576 16284 285 24399T5 18107 17745 161 21216T6 24874 24562 154 27668

M4SAs-cast 18053 16735 177 21757T5 18186 17913 132 19985T6 25358 25332 106 25735

M5SAs-cast 17648 16232 245 23492T5 19110 18402 176 22786T6 22209 22055 132 23996

12 Advances in Materials Science and Engineering

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

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indenter and a load of 60 kgf Ten measurements were madeper sample and the average value was reported as theRockwell hardness value of that alloy samplecondition

A computer-aided instrumented SATEC SI-1 UniversalImpact Testing Machine was used to carry out the impacttesting e instrument and the attached data acquisitionsystem provide the total absorbed energy (Et) of the sampleduring the impact test Five samples for each alloyconditionwere tested and the average value of the total energy ob-tained was reported

Samples for metallographic observation were sectionedfrom the test bars mounted and polished using standardpolishing procedures e polished samples were examinedusing an Olympus PMG3 optical microscope connected toa Clemex Vision PE image-analysis system A scanningelectron microscope (SEM JEOL JSM-6480LV) equippedwith energy dispersive X-ray spectrometer (EDS) was usedto investigate the intermetallic compounds and the fracturesurfaces

3 Results and Discussion

31 Microstructural Characterization

311 Intermetallic Compounds e volume fraction () ofintermetallic compounds observed in as-cast and as-quenched tensile bars is presented in Table 3 Figure 1compares backscattered electron (BSE) images of all alloysin the as-cast (left) and as-quenched (right) conditions ebackscattered images shown to the right in Figure 1 dem-onstrate clearly the reduction in the volume fraction of theintermetallic compounds in the as-quenched samples

For the as-cast condition it is obvious that the additionof Ni and Mn in different amounts and combinations(ie alloys M2S through M5S) significantly increases thevolume fraction of existing phases compared to the basealloy (cf 25 for alloy M1S and 1221 for alloy M4S)Alloy M4S which contains 4wt Ni shows an excessiveincrease in volume fraction in comparison to alloys M2SM3S andM5Sis substantial increase may be attributed tothe formation of Ni-containing phases such as Al3CuNiAl9FeNi and Al3Ni in addition to the phases commonlyobserved in other alloys such as the Q-phase Al2Cu Mg2Siand Fe-containing phases Other Ni-containing alloysie M2S andM5S contain almost the same phases howeverthe structure of alloy M4S uniquely comprises the eutecticAl-Al3Ni structure as shown in Figures 1(g) and 1(h) iseutectic structure is believed to increase the overall volumefraction of intermetallic compounds in alloy M4S

e addition of 075wt Mn to the base alloy ie alloyM3S doubles the volume fraction in the as-cast conditionand may be ascribed to the formation of α-Al15(FeMn)3Si2phase in script-like and sludge morphologies [28] In ad-dition the presence of the α-Al15(FeMn)3Si2 phase that doesnot dissolve with solution heat treatment would explain thenearly three times higher volume fraction observed in the as-quenched condition for alloy M3S compared to the basealloy M1S similar to the observations of Elgallad [19]

As may be seen from Table 3 and Figure 1 applyingsolution treatment reduces the volume fraction () of in-termetallic compounds owing to the dissolution of the Al2Cuphase and the partial dissolution of other phases such as Q-Al5Mg8Cu2Si6 Mg2Si Al3CuNi β-Al5FeSi π-Al8Mg3FeSi6and Al9FeNi [7]

312 Characteristics of Eutectic Silicon Particles e alloysstudied M1S through M5S were modified by adding200 ppm of strontium (Sr) erefore it is expected that theeutectic silicon particles will be modified to a large extent inthe as-cast condition in all alloys e morphology of eu-tectic silicon particles in the as-cast and as-quenched alloysamples is displayed in the optical micrographs shown inFigure 2 while the corresponding average Si particlecharacteristics are listed in Table 4 the average values wereobtained from measurements of 20 fields per alloysamplecondition

e optical micrographs shown in Figure 2 for the as-cast alloy samples on the left reveal that the majority ofsilicon particles are fully modified nevertheless partiallymodified silicon particles may still be observed in these

Table 3 Volume fractions () of undissolved intermetalliccompounds in the matrix of as-cast and as-quenched alloys

Volume fraction()

Alloy codeM1S M2S M3S M4S M5S

As-cast Average 251 617 434 1221 879SD 041 056 036 077 079

SHT Average 111 554 364 960 768SD 028 061 016 065 052

Table 1 Chemical composition of the alloys investigated in thisstudy

Chemical analysis (wt)

Alloycodes

ElementsSi Cu Mg Fe Ti Zr Ni Mn Sr Al

M1S 85 176 055 012 02 032 lt01 001 0022 BalM2S 84 17 060 014 021 033 19 001 0018 BalM3S 86 18 055 011 020 033 lt01 075 0020 BalM4S 86 18 067 012 022 029 4 001 0019 BalM5S 86 18 060 015 020 029 19 076 0018 Bal

Table 2 Heat treatment procedures and parameters applied toalloys studied

Heat treatment procedures and parametersHeattreatment

Solutiontreatment Quenching Aging

SHTlowast 495degC for 5 h Warm water(60degC) NA

T5 temper NA NA 180degC for 8 h

T6 temper 495degC for 5 h Warm water(60degC) 180degC for 8 h

SHT solution heat treatment

Advances in Materials Science and Engineering 3

(a) (b)

(c) (d)

(e) (f )

(g) (h)

Figure 1 Continued

4 Advances in Materials Science and Engineering

(i) (j)

Figure 1 Backscattered electron images for as-cast (left) and solution heat-treated (right) conditions of the alloys studied (a b) M1S (basealloy) (c d) M2S (2wt Ni) (e f ) M3S (075wt Mn) (g h) M4S (4wt Ni) and (i j) M5S (2wt Ni + 075 wt Mn)

(a) (b)

(c) (d)

(e) (f )

Figure 2 Continued

Advances in Materials Science and Engineering 5

micrographs to a certain extent e existence of thesepartially modified silicon particles could be a result of thehigh Mg content sim06 wt of the alloys It has been re-ported by Joenoes and Gruzleski [29] and Dunn and Dickert[30] that the presence of Mg and copper can change themicrostructure from a fully modified structure into a par-tially modified one due to the formation ofMg2Sr(Si Al) andAl-Cu-Sr phases which will result in reducing the amount ofavailable strontium (Sr) to achieve the required degree ofmodification of the eutectic silicon particles In the present

case however since the contents of Sr Cu and Mg are keptconstant in the alloys investigated other explanations aremandatory to explain the variations in the modification levelof the eutectic Si particles in these alloys

As per the micrographs shown in Figures 2(e) and 2(g)alloys M3S (354 + 002wt Sr + 03 wt Zr + 075wtMn) and M4S (354 + 002wt Sr + 03 wt Zr + 4wt Ni)appear to contain less amounts of partially modified eutecticsilicon is observation can be ascribed to the existingphases in the microstructure of the two alloys which may

(g) (h)

(i) (j)

Figure 2 Optical micrographs at 500X showing the morphology of the eutectic silicon in the alloys studied (left) as-cast conditions and(right) solution heat-treated conditions (a) as-cast alloy M1S (b) SHTalloy M1S (c) as-cast alloy M2S (d) SHTalloy M2S (e) as-cast alloyM3S (f ) SHT alloy M3S (g) as-cast alloy M4S (h) SHT alloy M4S (i) as-cast alloy M5S and (j) SHT alloy M5S

Table 4 Characteristics of eutectic silicon particles in as-cast and solution heat-treated conditions of the alloys studied

Alloy code and conditionParticle area

(μm2)Particle length

(μm) Aspect ratio Roundness () Sphericity ()

Av SD Av SD Av SD Av SD Av SDM1S-AC 285 439 267 248 196 133 049 021 075 028M1S-SHT 371 471 260 210 171 149 058 019 085 021M2S-AC 353 760 283 329 196 244 050 023 074 030M2S-SHT 567 808 327 295 179 127 056 020 081 023M3S-AC 192 310 214 222 192 243 051 022 077 028M3S-SHT 535 604 312 232 169 292 061 017 086 019M4S-AC 311 661 265 330 202 358 050 025 073 032M4S-SHT 399 553 268 243 186 265 056 022 082 023M5S-AC 387 688 312 343 212 627 048 022 070 030M5S-SHT 570 744 352 320 195 360 054 020 078 025

6 Advances in Materials Science and Engineering

contribute to variations in the free content of silicon andorstrontium Such variations may lead to a more efficientmodification in the case of a lower SiSr ratio and vice versa

On one hand a high amount of the copper in alloy M4S(containing 4 Ni) is consumed in forming Al3NiCu phase[11] and thus the possibility of forming the Al-Cu-Sr phasereported by Joenoes and Gruzleski [29] will be reducedConsequently more Sr will not be consumed to form the Al-Cu-Sr phase and thus better modification would be ex-pected for Ni-containing alloys particularly those withhigher Ni-content as in alloy M4S On the other hand theaddition of 075 wt Mn in alloy M3S changes some of theβ-Al5FeSi iron phase into Chinese script-like α-Al15(FeMn)3Si2 phase and sludge particles e mutual existence ofthe two Fe-based phases ie β-Al5FeSi and α-Al15(FeMn)3Si2 will lower the silicon content (ie reduce the Siphase) in alloy M3S to an extent which will allow a bettermodification level compared to that attained for the rest ofthe alloys studied as depicted in Figure 2(e)

ermal modification is yet another effective way toalter the morphology of eutectic silicon particles It isevident from the micrographs shown in Figure 2 on theright that the solution treatment changes the fibrousinterconnected eutectic silicon particles detected in the as-cast condition into globular particles with rounded edgese evolution of the morphology of the eutectic siliconparticles from fibrous to globular in these alloys is a directresult to the combined effect of solution-heat treatment andstrontium modification as previously stated by Chen et al[31] and Yuying et al [32]

It is evident from the data presented in Table 4 that theaverage Si particle area increases after solution treatment at495degC for 5 hours for all the alloys Additionally the sol-utionizing treatment produces a noticeable improvement inthe spheroidization of the Si particles concomitant withenhancements in the roundness values as can be seenqualitatively from the micrographs shown in Figure 2 eincrease in sphericity and roundness values would producea corresponding decrease in the aspect ratio as seen inTable 4

32 Mechanical Performance

321 Ambient-Temperature Tensile Testing In the presentstudy the sole addition of sim03 wt Zr to the 354-type Al-Si-Cu-Mg cast alloy (ie the base alloy M1S) in the as-castcondition enhances the ambient-temperature strengthvalues of the Zr-free 354 alloy (alloy A) used in previousinvestigations in the same group by Hernandez-Sandoval[16] by sim26MPa (UTS) and 40MPa (YS) respectivelyese enhancements in the strength values are accompaniedby a limited reduction in the alloy ductility (sim0054) Forthe solution heat-treated condition on the other hand theUTS and ductility values of the base alloy M1S remainvirtually constant at sim300MPa and sim63 respectivelywhile the yield strength increases by sim33MPa compared toalloy A in the work of Hernandez-Sandoval [16] e im-proved strength values of Zr-containing Al-Si-Cu-Mg alloy

emphasize the role of Zr addition in enhancing the ambient-temperature tensile properties

Figure 3 shows the ambient-temperature tensile prop-erties obtained for the alloys under investigation In the as-cast condition the base alloy M1S (354 + 03 wt Zr) showsthe lowest UTS and YS values As-cast strength values of theother alloys ie M2S through M5S show enhancements of14ndash25 and 16ndash26 in UTS and YS respectively comparedto the base alloy (M1S) However the ductility values ofalloys M2S through M5S show inconsistent variations withrespect to the ductility of the base alloy M1S these variationscomprise enhancements in case of alloy M3S deteriorationsin the case of alloys M4S and M5S and almost unchangedductility value in the case of alloy M2S

e probable explanations for the enhanced strengthvalues of alloy M3S are the formation of favorable phaseswhich are advantageous to the strength values and thehighly refined as-cast Si particles (Table 4) as a result to theaddition of 075 wt Mn to the base alloy (M1S) It is wellestablished that the addition of Mn neutralizes to someextent the deleterious effect of iron impurities by trans-forming the detrimental needle-like β-Al5FeSi phase into theless harmful α-Al15(Fe Mn)3Si2 phase which appears ineither script-like form or as blocky sludge particles or bothWhile there is no doubt about the positive effect of thescript-like α-phase on strength and ductility values there ismuch debate however on the effect of the sludge particleson the tensile properties either they are harmful as regularlybelieved [28 33 34] or favorable to the tensile properties[7 35 36] Garza-Elizondo [7] has reported that the presenceof these hard particles in the soft α-Al matrix may contributein enhancing the tensile properties through the developmentof more uniformly distributed stresses within the matrix

For the Ni-containing alloys enhancements in thestrength values can be correlated to the formation of Ni-containing intermetallic compounds such as Al9FeNiAl3CuNi and Al3Ni which can hinder the propagation ofcracks similar findings are reported in previous studies[11 16] Increasing the Ni content from 2wt to 4wtinversely affects the tensile properties at room temperatureIt is believed that the precipitation of higher volume frac-tions of the acicular Al9FeNi and Al3CuNi phases in the as-cast alloy M4S (4wt Ni) is responsible for the de-terioration of the tensile properties at room temperature

Apparently from Figure 3 the base alloy M1S proves tobe very responsive to solution heat treatment because itshows an increase of 40MPa and 8MPa in the as-cast UTSand YS values respectively after solutionizing at 495degC for 5hours In addition the ductility of the solutionizedM1S alloyalso shows an increase of sim5 over the ductility valueobtained for the as-cast condition On the other hand theother alloys ie M2S through M5S show small improve-ments in the range of 2ndash10MPa for UTS values anda noticeable reduction in YS values (18ndash36MPa) comparedto their strength values in the as-cast conditione ductilityvalues of alloys M2S through M5S increase after solutiontreatment e enhanced ductility values after solution heattreatment in particular are related to the changes in theeutectic silicon morphology Coarse acicular silicon particles

Advances in Materials Science and Engineering 7

serve as crack initiators which is the case in the as-castcondition whereas more spherical Si particles with roundededges and decreased aspect ratios are obtained in the so-lution heat-treated case

Figures 3(a) and 3(b) show that the strength values of thebase alloy M1S are 289MPa (UTS)259MPa (YS) and342MPa (UTS)325MPa (YS) in the T5- and T6-treatedconditions respectively Alloys M2S and M3S exhibit thehighest strength among the alloys studied with values of300MPa (UTS)277MPa (YS) and 315MPa (UTS)279MPa(YS) respectively in the T5-treated condition and 362MPa(UTS)352MPa (YS) and 357MPa (UTS)355MPa (YS) inthe T6-treated condition respectively e strength values(UTS and YS) of alloys M1S M2S (M1S+ 2wt Ni) andM3S (M1S+075wtMn) show distinct enhancements afterapplying the T6 treatment in comparison to the as-cast andas-solutionized conditions In contrast alloys M4S (M1S+4wt Ni) and M5S (M1S+2wt Ni+075wt Mn)exhibit a very limited enhancement in UTS (sim15MPa) after T6heat treatment with reference to their strength in the as-castand as-quenched conditions Additionally from Figure 3(c) itcan be seen that the ductility values reduce considerably afterT6 treatment when compared to the as-cast ductility values ofthe respective alloys Ductility values of the alloys studied arelimited in general due to the high silicon content sim9wt andthe presence of both Mg and Cu [30]

e enhanced strength values of alloy M2S particularlyfor the T6-treated condition can be attributed to thepresence of Ni-containing phases such as Al3Ni Al9FeNiand Al3CuNi in addition to the ne precipitates formedafter applying T6 treatment [37 38] With respect to alloyM3S the improved strength values following T5- and T6-heat treatments can be ascribed to (i) the presence ofα-Al15(Fe Mn)3Si2 in the form of blocky hard particles (ii)the precipitated strengthening Cu- and Mg-containingdispersoids and (iii) the probable formation of Al6Mnne dispersoids in the presence of a high Mn content of075 wt [39 40] e presence of these Mn dispersoidssignicantly improves the yield and ultimate strength valueswithout sacricing the ductility [39 41 42]

e presence of a high nickel content in T6-treated alloyM4S (4wt) results in deteriorating the ambient-temperature tensile properties as can be inferred fromFigure 3 similar observations have been noted by otherauthors [71043ndash46] is deterioration in the strengthvalues is a direct result of the high content of Ni which inturn will consume some of the available copper in the alloyto form the detected Al3CuNi phase As a result this willreduce the amount of copper available for strengtheningthrough precipitation hardening during heat treatment [10]Furthermore the precipitation of Al9FeNi and Al3CuNiphases in high volume fractions (Table 3) would facilitate

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(a)

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(b)

01234567

AC SHT T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

M1SM2SM3S

M4SM5S

(c)

Figure 3 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in as-cast solution heat-treated (SHT) and T5- andT6-treated conditions obtained at ambient temperature

8 Advances in Materials Science and Engineering

cracking since they would act as stress raisers causinginstability in the flow strain and hence the ductility of thisalloy will reduce accordingly

In general the room-temperature tensile properties inthe T6 heat-treated conditions are better than those obtainedwith the T5 treatment for the alloys studied e use ofpermanent mold casting which is the technique used forproducing the test bars would preserve copper and mag-nesium in considerable amounts in solid solution due to thehigh solidification rate us by applying artificial agingdirectly after solidification (ie T5 temper) large pro-portions of the dissolved Cu andMg in the solid solution willform strengthening dispersoids e T6 heat treatment onthe other hand involves solutionizing the as-cast structure ata sufficiently high temperature in order to dissolve higheramounts of Cu and Mg in solid solution in order to forma supersaturated solid solution upon quenching and toachieve further modification of the eutectic Si particlesus the artificial aging in the case of T6 treatment willprecipitate fine strengthening particles in larger proportionsthan in the case of T5 treatment which will enhance the alloystrength to a greater extent however at the expense ofductility

For the alloys studied the ambient-temperature tensiletesting data are listed in Table 5 along with the quality indexvalues which were calculated using Equations (1) and (2)according to the models developed by Drouzy et al [47] andCaceres [48] respectively

Q SUTS + dlog ef 1113857 (1)

Qc K (qn)n expminusqn + 04 log(100qn)1113858 1113859 (2)

where Q and Qc (MPa) are the quality indices according toDrouzy and Caceres models SUTS refers to the ultimatetensile strength (MPa) ef refers to the percentage elongationto fracture d is a material constant equal to 150MPaK is thestrength coefficient (MPa) relative quality index (q) and n isthe strain-hardening exponent

Figure 4 shows the quality chart for the alloys studiedbased on Drouzy [47] model and depicts variations in thequality index values based on the chemical composition andthe applied heat treatment Equations (1) and (3) were usedto develop the ldquoiso-Qrdquo and ldquoiso-YSrdquo lines in the chart

Sp(ys) aSUTS minus blog ef 1113857 + C (3)

where coefficients a b and c were quantified as 1 60MPaand minus13MPa respectively

e quality index values Q and Qc listed in Table 5 showthe same trend in variations however with different valuese difference between Q and Qc increases in the T5 and T6heat-treated conditions which can be accredited to the factthat the alloy quality is affected by the net amount by whichthe increase in strength is balanced by the reduction inductility As can be seen from Table 5 and Figure 4 the bestquality values for the alloys are obtained after solution heattreatment attributed to the microstructural changes thattake place during the solution treatment including thedissolution of strengthening elements the homogenization

of the segregated as-cast structure and the spheroidizationof the eutectic silicon particles ese changes will signifi-cantly enhance the alloy ductility in addition to a limitedenhancement in UTS values Consequently the quality in-dex values of the as-quenched (or solution heat-treated)alloys are remarkably higher than those in the as-castcondition

While the T6 heat treatment improves the UTS valuesconsiderably in comparison to the UTS values obtainedafter solution treatment it does so at the expense of theductility is trade-off between UTS and ductility valueswill certainly affect the quality index values and not nec-essarily in a positive way Likewise a similar behavior isnoted for the T5-treated alloys as well as can be inferredfrom Figure 4

It is evident that the superior ductility of the base alloyM1S is the main reason for the improved quality indices ofthis alloy in the majority of the conditions studied On theother hand the mutual enhancement in the strength andductility values of alloys M2S and M3S compared to those ofalloys M4S and M5S is responsible for the higher qualityindices of the former compared to those of the latter

e addition of Mn in alloy M3S results in transformingthe needles of the β-iron phase into the less detrimentalα-iron phase this favorable morphological change is be-lieved to improve the ductility and strength values of alloyM3S Whereas the structure of alloy M2S contains Ni-bearing phases with acicular morphologies and β-ironneedles that negatively affect the mechanical propertiesAccordingly the quality index values of alloy M3S are higherthan those of the 2wt Ni-containing alloy M2S in the as-cast SHT and T5 conditions In contrast the quality indexvalues of the T6-treated alloysM2S andM3S show a reversedbehavior according to the marginal variations in their tensileproperties and hence the quality index values

From Table 5 it is observable that the quality indexvalues calculated using Drouzyrsquos approach are higher thanthose obtained by the model developed by Caceres for alltreatment conditions per each alloy except for solution-treated conditions is can be attributed to the improvedductility of as-quenched conditions that will allow moreaccurate determination of the material parameters (K andn) us it would be advisable to calculate the quality indexvalues of solution-treated conditions using Caceresrsquo modelespecially for materials with low ductility at roomtemperature

322 Elevated-Temperature Tensile Testing Figure 5 revealsthe elevated-temperature tensile properties obtained at250degC for the alloys studied By tensile testing at 250degC allthe investigated alloys endure some softening owing to thepossible coarsening of the strengthening precipitates thatexist during tensile testing at room temperature (Figure 3)Figures 5(a) and 5(b) demonstrate that additions of Ni andMn in different amounts and combinations to the base alloyie alloys M2S through M5S slightly improve the strengthvalues of the base alloy in the range of 5ndash15MPa for both as-cast and T5-treated conditions e tight enhancement in

Advances in Materials Science and Engineering 9

strength values of the T5-treated conditions can be ascribed tothe limited variations in themicrostructural features of as-caststructures as well as to the low proportion of strengtheningprecipitates in the structure of T5-treated alloys

In regard to the ductility values in the as-cast conditionFigure 5(c) reveals that the highest ductility value is observedto be associated with the base alloy M1S with a value of

sim36 followed by the ductility of the Mn-containing alloysM3S andM5S and ending up with the lowest ductility valuesfor alloys M2S and M4S containing 2 and 4wt Ni re-spectively e higher ductility values of the as-cast Mn-containing alloys M3S andM5S can be attributed to the well-refined Si particles Table 4 and the transformation ofa considerable amount of β-Al5FeSi needles which may act

Table 5 Variation in average UTS YS El Qc and Q values of the alloys studied in as-cast SHT and T5- and T6-treated conditionsobtained at ambient temperature

Alloy Condition UTS(MPa)

YS(MPa)

Totalstrain ()

Plasticstrain () E (GPa) n K q Qc

(Equation (2))Q

(Equation (1))Difference

(QminusQc) (MPa)

M1S

As-cast 26086 19439 158 116 6266 018 58056 007 27788 29050 1262SHT 30034 20251 622 574 6250 017 57926 034 51236 41943 minus9293T5 28950 25875 094 048 6306 013 59169 004 21706 28543 6838T6 34195 32499 11075 056 6245 010 57691 006 28153 34860 6707

M2S

As-cast 32035 23585 163 116 6758 019 76378 006 34214 35219 1005SHT 32774 21261 320 270 6623 017 75932 016 53109 40343 minus12766T5 29997 27719 080 034 6564 015 70196 002 16710 28522 11812T6 36233 35157 080 024 6471 011 70779 002 19604 34816 15212

M3S

As-cast 32578 24572 176 126 6473 015 64889 008 35471 36255 784SHT 33475 20943 381 330 6447 012 64647 027 54926 42197 minus12729T5 31458 27939 098 049 6414 013 63449 004 23821 31310 7489T6 35701 35514 075 020 6432 008 62421 002 19202 33850 14648

M4S

As-cast 30440 22461 133 087 6610 020 83677 004 29364 32287 2923SHT 31232 20709 222 175 6656 018 82135 010 46959 36427 minus10532T5 27644 25414 071 031 6843 020 85707 002 9928 25451 15524T6 31598 31598 05705 011 6710 010 63474 001 7752 27941 20189

M5S

As-cast 29707 22659 127 083 6691 020 79201 004 27391 31280 3889SHT 29979 20664 199 154 6735 017 78035 009 43714 34462 minus9252T5 28461 27700 066 022 6474 015 72211 001 9720 25745 16025T6 31404 31404 056 011 6789 011 67764 001 4543 27632 23089

1

23

12

3

1 2

3

12

3

1 23

250

300

350

400

05 5

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

Drouzy quality index chart room temperature

M1SM2SM3S

M4SM5S

4 4

44

YS = 350 MPa

Q = 500 MPaQ = 450 MPa

Q = 350 MPa

Q = 250 MPa

Q = 300 MPa

Q = 400 MPa

YS = 250 MPa

4

1 as-cast2 SHT3 T54 T6

Figure 4 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast SHT and T5- and T6-treated conditions obtained at ambient temperature

10 Advances in Materials Science and Engineering

as crack initiators into the less detrimental α-Al15(MnFe)3Si2 phase with script-like andor sludge morphologies

e addition of Ni on the other hand lowers theductility values even for alloy M5S that contains 075wtMn when compared to alloy M3S which is Ni-free ereduction in ductility values of the as-cast Ni-containingalloys can be directly correlated to the presence of acicularNi-bearing phases with sharp edges such as Al3Ni Al9FeNiand Al3CuNi phases Variation in chemical compositionshas a limited eiexclect on the ductility values obtained at 250degCfor the T5-treated alloys since the maximum absolutediiexclerence in the ductility values of alloys M2S through M5Sis found to be sim044 Application of T5 and T6 heattreatments reduces the ductility observed in the as-castcondition e ductility values in the T6-treated conditionare generally lower than those obtained with T5 treatmentconditions

e application of the T6 heat treatment enhances thestrength values of as-cast conditions regardless the alloycomposition as shown in Figures 5(a) and 5(b) e en-hanced strength values of alloy M4S after T6 heat treatmentmay be attributed to the presence of δ-Al3CuNi and eutecticAl-Al3Ni phases that prove to contribute eiexclectively to theelevated-temperature strength of alloy M4S in spite ofa considerable amount of Cu that is consumed in formingthe δ-Al3CuNi phase which will certainly aiexclect the amount

of ne Al2Cu dispersoids formed which is consistent withthe ndings reported in references [38 49]

Interestingly alloys M3S (354 + 075wt Mn) and M4S(354 + 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the diiexclerent conditions ex-amined Moreover alloy M3S is considered to be morefavorable between the two since it exhibits higher ductilitythan that of the Ni-containing alloy M4S ese two alloysexhibit the best strength values (UTS and YS) in the T6-treated conditions among the investigated alloys whereasthe strength values of the other three alloys ie alloys M1SM2S and M5S are close to each other and lower than thestrength values obtained for alloys M3S and M4S bysim36MPa is observation would emphasize the advanta-geous role of adding Mn instead of Ni to enhance theelevated-temperature tensile properties along with its eco-nomic impact

Generally the closeness of the elevated-temperaturestrength values of the alloys studied can be credited tothe presence of 03 wt Zr in each alloy whereby theformation of the ne metastable L12-Al3Zr particles is ex-pected in the microstructures of all the alloys which in turnwill improve the alloy strength in a common manner

For elevated-temperature tensile properties the conceptof the quality index will be discussed according to theconcept of Drouzy et al [47] (Q) Table 6 demonstrates the

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditionsM1SM2SM3S

M4SM5S

(a)

M1SM2SM3S

M4SM5S

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditions

(b)

M1SM2SM3S

M4SM5S

005

115

225

335

445

AC T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

(c)

Figure 5 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in the as-cast solution heat-treated (SHT) and T5-and T6-treated conditions obtained at 250degC

Advances in Materials Science and Engineering 11

elevated-temperature tensile data along with the quality indexvalues (Q) of the alloys studied calculated using Equation (1)Figure 6 shows the quality chart obtained based on the cal-culations of Drouzy et al [47] As may be seen the qualityindex values obtained at 250degC do not show wide variation invalues as was observed in the case of the ambient-temperature data is limited variation can be understoodin light of the balanced variation in UTS and ductility valuesobtained at the elevated temperature of 250degC For examplethe base alloyM1S in the as-cast condition exhibits the highestductility value of 367 and a UTS value of 16995MPa whilethe lowest ductility is experienced by alloy M4S for the T6-treated condition with a value of 106 along with a UTSvalue of 25358MPa By calculating the quality indices of thesetwo conditions they revealQ values of 26395 and 25735MPafor as-cast M1S and T6-treated M4S respectively ose twoextreme conditions show that despite the considerable vari-ation in the UTS values on the one hand and ductility valueson the other for these two conditions the quality indices inboth cases remain almost unchanged due to the balancedtrade-off between the UTS and ductility values e relativelylowUTS and ductility values obtained at elevated temperature(250degC) for the T5-treated condition result in the T5-treatedalloys exhibiting minimum Q values among the conditionsstudied

Another interesting observation is that the quality indexvalues for alloys M2S and M3S in the T6-treated conditionare found to be the maximum for the alloys and conditionsstudied is observation highlights the enhanced charac-teristics of alloy M3S which contains 075wt Mn andemphasizes the positive influence of the high Mn-additionon the elevated-temperature tensile properties which arefound to be more or less comparable to those obtained withthe addition of 2 and 4wt Ni to the same base alloy

e favorable role of the blocky α-Al15(Fe Mn)3Si2phase termed as sludge particles in improving the tensileproperties of alloy M3S at 25degC and 250degC can be witnessed

from the fractograph of alloy M3S after testing at 250degCpresented in Figure 7 e sludge particles appear to retardthe propagation of the cracks developed in the other phaseswhich will subsequently enhance the mechanical propertiesof the respective alloy Yet another interesting observationmade from this figure is that while many of the intermetallicphase particles appear cracked as indicated by the solidarrows the sludge particles however are crack-freeWhereas the multiple cracked Ni-rich phases exist on thefracture surface of alloy M2S after testing at 250degC are be-lieved to contribute to the crack initiation process and hencedeteriorate the tensile properties of this alloy as witnessed inFigure 8

323 Hardness Values Figure 9 illustrates the variation inthe hardness values of the alloys as a function of the appliedheat treatment At first glance one can observe from Figure 9that the hardness values of different alloys show insignificantvariations for the same conditions For each alloy the peak-aged condition exhibits the highest hardness value among allconditions Also the tailored alloys ie M2S through M5Sshow better hardness values than those obtained for the basealloy in all the conditions studied

Variations in hardness values of the alloys in the as-castcondition can be attributed to the additions of Ni andor Mnmade to the base alloy M1S It was seen that additions of Niandor Mn in various amounts increased the volume frac-tions of intermetallic compounds considerably as listed inTable 3 e variations in hardness values follow the sametrend as variations in the percentage volume fraction ofintermetallic compounds us the base alloy M1S exhibitsthe lowest hardness value in the as-cast condition having thelowest volume fraction according to Table 3 and the highesthardness value of the same condition is associated with alloyM4S that has the highest volume fraction of intermetalliccompounds is observation highlights the effective role ofintermetallic compounds in enhancing the hardness values[19 50]

e dissolution of the strengthening elements over thecourse of the solution treatment reduces the hardness valuesin spite of the expected improved homogeneity in com-position and evolution of the eutectic silicon morphologyfollowing solution treatment is behavior emphasizes thecrucial role of intermetallic phases in influencing the me-chanical performance of alloys It is established that thehardness value of a specific alloy corresponds to the com-bination of the tensile yield strength and work-hardeningrate of the alloy [50 51] e order of the alloys studiedaccording to the hardness value in the as-quenched con-dition matches to a large extent their order with respect totheir yield strength in the same as-quenched condition(Figure 3)

Direct artificial aging following casting of test barsie T5-temper treatment introduces slight improvements inthe hardness values with respect to those obtained for the as-cast condition is can be attributed to the limited changesin the microstructure of the as-cast alloysbars followingdirect artificial aging without solution treatment e slight

Table 6 Variation in average UTS YS El and Q values of thealloys studied in as-cast and T5- and T6-treated conditions ob-tained at 250degC

Alloy Condition UTS(MPa)

YS(MPa) El Q (Equation (1))

M1SAs-cast 16995 15756 367 25465T5 17207 16151 202 21791T6 21765 21365 192 26014

M2SAs-cast 18632 17284 225 23915T5 19625 17885 160 22671T6 22372 22233 215 27365

M3SAs-cast 17576 16284 285 24399T5 18107 17745 161 21216T6 24874 24562 154 27668

M4SAs-cast 18053 16735 177 21757T5 18186 17913 132 19985T6 25358 25332 106 25735

M5SAs-cast 17648 16232 245 23492T5 19110 18402 176 22786T6 22209 22055 132 23996

12 Advances in Materials Science and Engineering

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

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Submit your manuscripts atwwwhindawicom

(a) (b)

(c) (d)

(e) (f )

(g) (h)

Figure 1 Continued

4 Advances in Materials Science and Engineering

(i) (j)

Figure 1 Backscattered electron images for as-cast (left) and solution heat-treated (right) conditions of the alloys studied (a b) M1S (basealloy) (c d) M2S (2wt Ni) (e f ) M3S (075wt Mn) (g h) M4S (4wt Ni) and (i j) M5S (2wt Ni + 075 wt Mn)

(a) (b)

(c) (d)

(e) (f )

Figure 2 Continued

Advances in Materials Science and Engineering 5

micrographs to a certain extent e existence of thesepartially modified silicon particles could be a result of thehigh Mg content sim06 wt of the alloys It has been re-ported by Joenoes and Gruzleski [29] and Dunn and Dickert[30] that the presence of Mg and copper can change themicrostructure from a fully modified structure into a par-tially modified one due to the formation ofMg2Sr(Si Al) andAl-Cu-Sr phases which will result in reducing the amount ofavailable strontium (Sr) to achieve the required degree ofmodification of the eutectic silicon particles In the present

case however since the contents of Sr Cu and Mg are keptconstant in the alloys investigated other explanations aremandatory to explain the variations in the modification levelof the eutectic Si particles in these alloys

As per the micrographs shown in Figures 2(e) and 2(g)alloys M3S (354 + 002wt Sr + 03 wt Zr + 075wtMn) and M4S (354 + 002wt Sr + 03 wt Zr + 4wt Ni)appear to contain less amounts of partially modified eutecticsilicon is observation can be ascribed to the existingphases in the microstructure of the two alloys which may

(g) (h)

(i) (j)

Figure 2 Optical micrographs at 500X showing the morphology of the eutectic silicon in the alloys studied (left) as-cast conditions and(right) solution heat-treated conditions (a) as-cast alloy M1S (b) SHTalloy M1S (c) as-cast alloy M2S (d) SHTalloy M2S (e) as-cast alloyM3S (f ) SHT alloy M3S (g) as-cast alloy M4S (h) SHT alloy M4S (i) as-cast alloy M5S and (j) SHT alloy M5S

Table 4 Characteristics of eutectic silicon particles in as-cast and solution heat-treated conditions of the alloys studied

Alloy code and conditionParticle area

(μm2)Particle length

(μm) Aspect ratio Roundness () Sphericity ()

Av SD Av SD Av SD Av SD Av SDM1S-AC 285 439 267 248 196 133 049 021 075 028M1S-SHT 371 471 260 210 171 149 058 019 085 021M2S-AC 353 760 283 329 196 244 050 023 074 030M2S-SHT 567 808 327 295 179 127 056 020 081 023M3S-AC 192 310 214 222 192 243 051 022 077 028M3S-SHT 535 604 312 232 169 292 061 017 086 019M4S-AC 311 661 265 330 202 358 050 025 073 032M4S-SHT 399 553 268 243 186 265 056 022 082 023M5S-AC 387 688 312 343 212 627 048 022 070 030M5S-SHT 570 744 352 320 195 360 054 020 078 025

6 Advances in Materials Science and Engineering

contribute to variations in the free content of silicon andorstrontium Such variations may lead to a more efficientmodification in the case of a lower SiSr ratio and vice versa

On one hand a high amount of the copper in alloy M4S(containing 4 Ni) is consumed in forming Al3NiCu phase[11] and thus the possibility of forming the Al-Cu-Sr phasereported by Joenoes and Gruzleski [29] will be reducedConsequently more Sr will not be consumed to form the Al-Cu-Sr phase and thus better modification would be ex-pected for Ni-containing alloys particularly those withhigher Ni-content as in alloy M4S On the other hand theaddition of 075 wt Mn in alloy M3S changes some of theβ-Al5FeSi iron phase into Chinese script-like α-Al15(FeMn)3Si2 phase and sludge particles e mutual existence ofthe two Fe-based phases ie β-Al5FeSi and α-Al15(FeMn)3Si2 will lower the silicon content (ie reduce the Siphase) in alloy M3S to an extent which will allow a bettermodification level compared to that attained for the rest ofthe alloys studied as depicted in Figure 2(e)

ermal modification is yet another effective way toalter the morphology of eutectic silicon particles It isevident from the micrographs shown in Figure 2 on theright that the solution treatment changes the fibrousinterconnected eutectic silicon particles detected in the as-cast condition into globular particles with rounded edgese evolution of the morphology of the eutectic siliconparticles from fibrous to globular in these alloys is a directresult to the combined effect of solution-heat treatment andstrontium modification as previously stated by Chen et al[31] and Yuying et al [32]

It is evident from the data presented in Table 4 that theaverage Si particle area increases after solution treatment at495degC for 5 hours for all the alloys Additionally the sol-utionizing treatment produces a noticeable improvement inthe spheroidization of the Si particles concomitant withenhancements in the roundness values as can be seenqualitatively from the micrographs shown in Figure 2 eincrease in sphericity and roundness values would producea corresponding decrease in the aspect ratio as seen inTable 4

32 Mechanical Performance

321 Ambient-Temperature Tensile Testing In the presentstudy the sole addition of sim03 wt Zr to the 354-type Al-Si-Cu-Mg cast alloy (ie the base alloy M1S) in the as-castcondition enhances the ambient-temperature strengthvalues of the Zr-free 354 alloy (alloy A) used in previousinvestigations in the same group by Hernandez-Sandoval[16] by sim26MPa (UTS) and 40MPa (YS) respectivelyese enhancements in the strength values are accompaniedby a limited reduction in the alloy ductility (sim0054) Forthe solution heat-treated condition on the other hand theUTS and ductility values of the base alloy M1S remainvirtually constant at sim300MPa and sim63 respectivelywhile the yield strength increases by sim33MPa compared toalloy A in the work of Hernandez-Sandoval [16] e im-proved strength values of Zr-containing Al-Si-Cu-Mg alloy

emphasize the role of Zr addition in enhancing the ambient-temperature tensile properties

Figure 3 shows the ambient-temperature tensile prop-erties obtained for the alloys under investigation In the as-cast condition the base alloy M1S (354 + 03 wt Zr) showsthe lowest UTS and YS values As-cast strength values of theother alloys ie M2S through M5S show enhancements of14ndash25 and 16ndash26 in UTS and YS respectively comparedto the base alloy (M1S) However the ductility values ofalloys M2S through M5S show inconsistent variations withrespect to the ductility of the base alloy M1S these variationscomprise enhancements in case of alloy M3S deteriorationsin the case of alloys M4S and M5S and almost unchangedductility value in the case of alloy M2S

e probable explanations for the enhanced strengthvalues of alloy M3S are the formation of favorable phaseswhich are advantageous to the strength values and thehighly refined as-cast Si particles (Table 4) as a result to theaddition of 075 wt Mn to the base alloy (M1S) It is wellestablished that the addition of Mn neutralizes to someextent the deleterious effect of iron impurities by trans-forming the detrimental needle-like β-Al5FeSi phase into theless harmful α-Al15(Fe Mn)3Si2 phase which appears ineither script-like form or as blocky sludge particles or bothWhile there is no doubt about the positive effect of thescript-like α-phase on strength and ductility values there ismuch debate however on the effect of the sludge particleson the tensile properties either they are harmful as regularlybelieved [28 33 34] or favorable to the tensile properties[7 35 36] Garza-Elizondo [7] has reported that the presenceof these hard particles in the soft α-Al matrix may contributein enhancing the tensile properties through the developmentof more uniformly distributed stresses within the matrix

For the Ni-containing alloys enhancements in thestrength values can be correlated to the formation of Ni-containing intermetallic compounds such as Al9FeNiAl3CuNi and Al3Ni which can hinder the propagation ofcracks similar findings are reported in previous studies[11 16] Increasing the Ni content from 2wt to 4wtinversely affects the tensile properties at room temperatureIt is believed that the precipitation of higher volume frac-tions of the acicular Al9FeNi and Al3CuNi phases in the as-cast alloy M4S (4wt Ni) is responsible for the de-terioration of the tensile properties at room temperature

Apparently from Figure 3 the base alloy M1S proves tobe very responsive to solution heat treatment because itshows an increase of 40MPa and 8MPa in the as-cast UTSand YS values respectively after solutionizing at 495degC for 5hours In addition the ductility of the solutionizedM1S alloyalso shows an increase of sim5 over the ductility valueobtained for the as-cast condition On the other hand theother alloys ie M2S through M5S show small improve-ments in the range of 2ndash10MPa for UTS values anda noticeable reduction in YS values (18ndash36MPa) comparedto their strength values in the as-cast conditione ductilityvalues of alloys M2S through M5S increase after solutiontreatment e enhanced ductility values after solution heattreatment in particular are related to the changes in theeutectic silicon morphology Coarse acicular silicon particles

Advances in Materials Science and Engineering 7

serve as crack initiators which is the case in the as-castcondition whereas more spherical Si particles with roundededges and decreased aspect ratios are obtained in the so-lution heat-treated case

Figures 3(a) and 3(b) show that the strength values of thebase alloy M1S are 289MPa (UTS)259MPa (YS) and342MPa (UTS)325MPa (YS) in the T5- and T6-treatedconditions respectively Alloys M2S and M3S exhibit thehighest strength among the alloys studied with values of300MPa (UTS)277MPa (YS) and 315MPa (UTS)279MPa(YS) respectively in the T5-treated condition and 362MPa(UTS)352MPa (YS) and 357MPa (UTS)355MPa (YS) inthe T6-treated condition respectively e strength values(UTS and YS) of alloys M1S M2S (M1S+ 2wt Ni) andM3S (M1S+075wtMn) show distinct enhancements afterapplying the T6 treatment in comparison to the as-cast andas-solutionized conditions In contrast alloys M4S (M1S+4wt Ni) and M5S (M1S+2wt Ni+075wt Mn)exhibit a very limited enhancement in UTS (sim15MPa) after T6heat treatment with reference to their strength in the as-castand as-quenched conditions Additionally from Figure 3(c) itcan be seen that the ductility values reduce considerably afterT6 treatment when compared to the as-cast ductility values ofthe respective alloys Ductility values of the alloys studied arelimited in general due to the high silicon content sim9wt andthe presence of both Mg and Cu [30]

e enhanced strength values of alloy M2S particularlyfor the T6-treated condition can be attributed to thepresence of Ni-containing phases such as Al3Ni Al9FeNiand Al3CuNi in addition to the ne precipitates formedafter applying T6 treatment [37 38] With respect to alloyM3S the improved strength values following T5- and T6-heat treatments can be ascribed to (i) the presence ofα-Al15(Fe Mn)3Si2 in the form of blocky hard particles (ii)the precipitated strengthening Cu- and Mg-containingdispersoids and (iii) the probable formation of Al6Mnne dispersoids in the presence of a high Mn content of075 wt [39 40] e presence of these Mn dispersoidssignicantly improves the yield and ultimate strength valueswithout sacricing the ductility [39 41 42]

e presence of a high nickel content in T6-treated alloyM4S (4wt) results in deteriorating the ambient-temperature tensile properties as can be inferred fromFigure 3 similar observations have been noted by otherauthors [71043ndash46] is deterioration in the strengthvalues is a direct result of the high content of Ni which inturn will consume some of the available copper in the alloyto form the detected Al3CuNi phase As a result this willreduce the amount of copper available for strengtheningthrough precipitation hardening during heat treatment [10]Furthermore the precipitation of Al9FeNi and Al3CuNiphases in high volume fractions (Table 3) would facilitate

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(a)

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(b)

01234567

AC SHT T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

M1SM2SM3S

M4SM5S

(c)

Figure 3 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in as-cast solution heat-treated (SHT) and T5- andT6-treated conditions obtained at ambient temperature

8 Advances in Materials Science and Engineering

cracking since they would act as stress raisers causinginstability in the flow strain and hence the ductility of thisalloy will reduce accordingly

In general the room-temperature tensile properties inthe T6 heat-treated conditions are better than those obtainedwith the T5 treatment for the alloys studied e use ofpermanent mold casting which is the technique used forproducing the test bars would preserve copper and mag-nesium in considerable amounts in solid solution due to thehigh solidification rate us by applying artificial agingdirectly after solidification (ie T5 temper) large pro-portions of the dissolved Cu andMg in the solid solution willform strengthening dispersoids e T6 heat treatment onthe other hand involves solutionizing the as-cast structure ata sufficiently high temperature in order to dissolve higheramounts of Cu and Mg in solid solution in order to forma supersaturated solid solution upon quenching and toachieve further modification of the eutectic Si particlesus the artificial aging in the case of T6 treatment willprecipitate fine strengthening particles in larger proportionsthan in the case of T5 treatment which will enhance the alloystrength to a greater extent however at the expense ofductility

For the alloys studied the ambient-temperature tensiletesting data are listed in Table 5 along with the quality indexvalues which were calculated using Equations (1) and (2)according to the models developed by Drouzy et al [47] andCaceres [48] respectively

Q SUTS + dlog ef 1113857 (1)

Qc K (qn)n expminusqn + 04 log(100qn)1113858 1113859 (2)

where Q and Qc (MPa) are the quality indices according toDrouzy and Caceres models SUTS refers to the ultimatetensile strength (MPa) ef refers to the percentage elongationto fracture d is a material constant equal to 150MPaK is thestrength coefficient (MPa) relative quality index (q) and n isthe strain-hardening exponent

Figure 4 shows the quality chart for the alloys studiedbased on Drouzy [47] model and depicts variations in thequality index values based on the chemical composition andthe applied heat treatment Equations (1) and (3) were usedto develop the ldquoiso-Qrdquo and ldquoiso-YSrdquo lines in the chart

Sp(ys) aSUTS minus blog ef 1113857 + C (3)

where coefficients a b and c were quantified as 1 60MPaand minus13MPa respectively

e quality index values Q and Qc listed in Table 5 showthe same trend in variations however with different valuese difference between Q and Qc increases in the T5 and T6heat-treated conditions which can be accredited to the factthat the alloy quality is affected by the net amount by whichthe increase in strength is balanced by the reduction inductility As can be seen from Table 5 and Figure 4 the bestquality values for the alloys are obtained after solution heattreatment attributed to the microstructural changes thattake place during the solution treatment including thedissolution of strengthening elements the homogenization

of the segregated as-cast structure and the spheroidizationof the eutectic silicon particles ese changes will signifi-cantly enhance the alloy ductility in addition to a limitedenhancement in UTS values Consequently the quality in-dex values of the as-quenched (or solution heat-treated)alloys are remarkably higher than those in the as-castcondition

While the T6 heat treatment improves the UTS valuesconsiderably in comparison to the UTS values obtainedafter solution treatment it does so at the expense of theductility is trade-off between UTS and ductility valueswill certainly affect the quality index values and not nec-essarily in a positive way Likewise a similar behavior isnoted for the T5-treated alloys as well as can be inferredfrom Figure 4

It is evident that the superior ductility of the base alloyM1S is the main reason for the improved quality indices ofthis alloy in the majority of the conditions studied On theother hand the mutual enhancement in the strength andductility values of alloys M2S and M3S compared to those ofalloys M4S and M5S is responsible for the higher qualityindices of the former compared to those of the latter

e addition of Mn in alloy M3S results in transformingthe needles of the β-iron phase into the less detrimentalα-iron phase this favorable morphological change is be-lieved to improve the ductility and strength values of alloyM3S Whereas the structure of alloy M2S contains Ni-bearing phases with acicular morphologies and β-ironneedles that negatively affect the mechanical propertiesAccordingly the quality index values of alloy M3S are higherthan those of the 2wt Ni-containing alloy M2S in the as-cast SHT and T5 conditions In contrast the quality indexvalues of the T6-treated alloysM2S andM3S show a reversedbehavior according to the marginal variations in their tensileproperties and hence the quality index values

From Table 5 it is observable that the quality indexvalues calculated using Drouzyrsquos approach are higher thanthose obtained by the model developed by Caceres for alltreatment conditions per each alloy except for solution-treated conditions is can be attributed to the improvedductility of as-quenched conditions that will allow moreaccurate determination of the material parameters (K andn) us it would be advisable to calculate the quality indexvalues of solution-treated conditions using Caceresrsquo modelespecially for materials with low ductility at roomtemperature

322 Elevated-Temperature Tensile Testing Figure 5 revealsthe elevated-temperature tensile properties obtained at250degC for the alloys studied By tensile testing at 250degC allthe investigated alloys endure some softening owing to thepossible coarsening of the strengthening precipitates thatexist during tensile testing at room temperature (Figure 3)Figures 5(a) and 5(b) demonstrate that additions of Ni andMn in different amounts and combinations to the base alloyie alloys M2S through M5S slightly improve the strengthvalues of the base alloy in the range of 5ndash15MPa for both as-cast and T5-treated conditions e tight enhancement in

Advances in Materials Science and Engineering 9

strength values of the T5-treated conditions can be ascribed tothe limited variations in themicrostructural features of as-caststructures as well as to the low proportion of strengtheningprecipitates in the structure of T5-treated alloys

In regard to the ductility values in the as-cast conditionFigure 5(c) reveals that the highest ductility value is observedto be associated with the base alloy M1S with a value of

sim36 followed by the ductility of the Mn-containing alloysM3S andM5S and ending up with the lowest ductility valuesfor alloys M2S and M4S containing 2 and 4wt Ni re-spectively e higher ductility values of the as-cast Mn-containing alloys M3S andM5S can be attributed to the well-refined Si particles Table 4 and the transformation ofa considerable amount of β-Al5FeSi needles which may act

Table 5 Variation in average UTS YS El Qc and Q values of the alloys studied in as-cast SHT and T5- and T6-treated conditionsobtained at ambient temperature

Alloy Condition UTS(MPa)

YS(MPa)

Totalstrain ()

Plasticstrain () E (GPa) n K q Qc

(Equation (2))Q

(Equation (1))Difference

(QminusQc) (MPa)

M1S

As-cast 26086 19439 158 116 6266 018 58056 007 27788 29050 1262SHT 30034 20251 622 574 6250 017 57926 034 51236 41943 minus9293T5 28950 25875 094 048 6306 013 59169 004 21706 28543 6838T6 34195 32499 11075 056 6245 010 57691 006 28153 34860 6707

M2S

As-cast 32035 23585 163 116 6758 019 76378 006 34214 35219 1005SHT 32774 21261 320 270 6623 017 75932 016 53109 40343 minus12766T5 29997 27719 080 034 6564 015 70196 002 16710 28522 11812T6 36233 35157 080 024 6471 011 70779 002 19604 34816 15212

M3S

As-cast 32578 24572 176 126 6473 015 64889 008 35471 36255 784SHT 33475 20943 381 330 6447 012 64647 027 54926 42197 minus12729T5 31458 27939 098 049 6414 013 63449 004 23821 31310 7489T6 35701 35514 075 020 6432 008 62421 002 19202 33850 14648

M4S

As-cast 30440 22461 133 087 6610 020 83677 004 29364 32287 2923SHT 31232 20709 222 175 6656 018 82135 010 46959 36427 minus10532T5 27644 25414 071 031 6843 020 85707 002 9928 25451 15524T6 31598 31598 05705 011 6710 010 63474 001 7752 27941 20189

M5S

As-cast 29707 22659 127 083 6691 020 79201 004 27391 31280 3889SHT 29979 20664 199 154 6735 017 78035 009 43714 34462 minus9252T5 28461 27700 066 022 6474 015 72211 001 9720 25745 16025T6 31404 31404 056 011 6789 011 67764 001 4543 27632 23089

1

23

12

3

1 2

3

12

3

1 23

250

300

350

400

05 5

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

Drouzy quality index chart room temperature

M1SM2SM3S

M4SM5S

4 4

44

YS = 350 MPa

Q = 500 MPaQ = 450 MPa

Q = 350 MPa

Q = 250 MPa

Q = 300 MPa

Q = 400 MPa

YS = 250 MPa

4

1 as-cast2 SHT3 T54 T6

Figure 4 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast SHT and T5- and T6-treated conditions obtained at ambient temperature

10 Advances in Materials Science and Engineering

as crack initiators into the less detrimental α-Al15(MnFe)3Si2 phase with script-like andor sludge morphologies

e addition of Ni on the other hand lowers theductility values even for alloy M5S that contains 075wtMn when compared to alloy M3S which is Ni-free ereduction in ductility values of the as-cast Ni-containingalloys can be directly correlated to the presence of acicularNi-bearing phases with sharp edges such as Al3Ni Al9FeNiand Al3CuNi phases Variation in chemical compositionshas a limited eiexclect on the ductility values obtained at 250degCfor the T5-treated alloys since the maximum absolutediiexclerence in the ductility values of alloys M2S through M5Sis found to be sim044 Application of T5 and T6 heattreatments reduces the ductility observed in the as-castcondition e ductility values in the T6-treated conditionare generally lower than those obtained with T5 treatmentconditions

e application of the T6 heat treatment enhances thestrength values of as-cast conditions regardless the alloycomposition as shown in Figures 5(a) and 5(b) e en-hanced strength values of alloy M4S after T6 heat treatmentmay be attributed to the presence of δ-Al3CuNi and eutecticAl-Al3Ni phases that prove to contribute eiexclectively to theelevated-temperature strength of alloy M4S in spite ofa considerable amount of Cu that is consumed in formingthe δ-Al3CuNi phase which will certainly aiexclect the amount

of ne Al2Cu dispersoids formed which is consistent withthe ndings reported in references [38 49]

Interestingly alloys M3S (354 + 075wt Mn) and M4S(354 + 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the diiexclerent conditions ex-amined Moreover alloy M3S is considered to be morefavorable between the two since it exhibits higher ductilitythan that of the Ni-containing alloy M4S ese two alloysexhibit the best strength values (UTS and YS) in the T6-treated conditions among the investigated alloys whereasthe strength values of the other three alloys ie alloys M1SM2S and M5S are close to each other and lower than thestrength values obtained for alloys M3S and M4S bysim36MPa is observation would emphasize the advanta-geous role of adding Mn instead of Ni to enhance theelevated-temperature tensile properties along with its eco-nomic impact

Generally the closeness of the elevated-temperaturestrength values of the alloys studied can be credited tothe presence of 03 wt Zr in each alloy whereby theformation of the ne metastable L12-Al3Zr particles is ex-pected in the microstructures of all the alloys which in turnwill improve the alloy strength in a common manner

For elevated-temperature tensile properties the conceptof the quality index will be discussed according to theconcept of Drouzy et al [47] (Q) Table 6 demonstrates the

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditionsM1SM2SM3S

M4SM5S

(a)

M1SM2SM3S

M4SM5S

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditions

(b)

M1SM2SM3S

M4SM5S

005

115

225

335

445

AC T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

(c)

Figure 5 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in the as-cast solution heat-treated (SHT) and T5-and T6-treated conditions obtained at 250degC

Advances in Materials Science and Engineering 11

elevated-temperature tensile data along with the quality indexvalues (Q) of the alloys studied calculated using Equation (1)Figure 6 shows the quality chart obtained based on the cal-culations of Drouzy et al [47] As may be seen the qualityindex values obtained at 250degC do not show wide variation invalues as was observed in the case of the ambient-temperature data is limited variation can be understoodin light of the balanced variation in UTS and ductility valuesobtained at the elevated temperature of 250degC For examplethe base alloyM1S in the as-cast condition exhibits the highestductility value of 367 and a UTS value of 16995MPa whilethe lowest ductility is experienced by alloy M4S for the T6-treated condition with a value of 106 along with a UTSvalue of 25358MPa By calculating the quality indices of thesetwo conditions they revealQ values of 26395 and 25735MPafor as-cast M1S and T6-treated M4S respectively ose twoextreme conditions show that despite the considerable vari-ation in the UTS values on the one hand and ductility valueson the other for these two conditions the quality indices inboth cases remain almost unchanged due to the balancedtrade-off between the UTS and ductility values e relativelylowUTS and ductility values obtained at elevated temperature(250degC) for the T5-treated condition result in the T5-treatedalloys exhibiting minimum Q values among the conditionsstudied

Another interesting observation is that the quality indexvalues for alloys M2S and M3S in the T6-treated conditionare found to be the maximum for the alloys and conditionsstudied is observation highlights the enhanced charac-teristics of alloy M3S which contains 075wt Mn andemphasizes the positive influence of the high Mn-additionon the elevated-temperature tensile properties which arefound to be more or less comparable to those obtained withthe addition of 2 and 4wt Ni to the same base alloy

e favorable role of the blocky α-Al15(Fe Mn)3Si2phase termed as sludge particles in improving the tensileproperties of alloy M3S at 25degC and 250degC can be witnessed

from the fractograph of alloy M3S after testing at 250degCpresented in Figure 7 e sludge particles appear to retardthe propagation of the cracks developed in the other phaseswhich will subsequently enhance the mechanical propertiesof the respective alloy Yet another interesting observationmade from this figure is that while many of the intermetallicphase particles appear cracked as indicated by the solidarrows the sludge particles however are crack-freeWhereas the multiple cracked Ni-rich phases exist on thefracture surface of alloy M2S after testing at 250degC are be-lieved to contribute to the crack initiation process and hencedeteriorate the tensile properties of this alloy as witnessed inFigure 8

323 Hardness Values Figure 9 illustrates the variation inthe hardness values of the alloys as a function of the appliedheat treatment At first glance one can observe from Figure 9that the hardness values of different alloys show insignificantvariations for the same conditions For each alloy the peak-aged condition exhibits the highest hardness value among allconditions Also the tailored alloys ie M2S through M5Sshow better hardness values than those obtained for the basealloy in all the conditions studied

Variations in hardness values of the alloys in the as-castcondition can be attributed to the additions of Ni andor Mnmade to the base alloy M1S It was seen that additions of Niandor Mn in various amounts increased the volume frac-tions of intermetallic compounds considerably as listed inTable 3 e variations in hardness values follow the sametrend as variations in the percentage volume fraction ofintermetallic compounds us the base alloy M1S exhibitsthe lowest hardness value in the as-cast condition having thelowest volume fraction according to Table 3 and the highesthardness value of the same condition is associated with alloyM4S that has the highest volume fraction of intermetalliccompounds is observation highlights the effective role ofintermetallic compounds in enhancing the hardness values[19 50]

e dissolution of the strengthening elements over thecourse of the solution treatment reduces the hardness valuesin spite of the expected improved homogeneity in com-position and evolution of the eutectic silicon morphologyfollowing solution treatment is behavior emphasizes thecrucial role of intermetallic phases in influencing the me-chanical performance of alloys It is established that thehardness value of a specific alloy corresponds to the com-bination of the tensile yield strength and work-hardeningrate of the alloy [50 51] e order of the alloys studiedaccording to the hardness value in the as-quenched con-dition matches to a large extent their order with respect totheir yield strength in the same as-quenched condition(Figure 3)

Direct artificial aging following casting of test barsie T5-temper treatment introduces slight improvements inthe hardness values with respect to those obtained for the as-cast condition is can be attributed to the limited changesin the microstructure of the as-cast alloysbars followingdirect artificial aging without solution treatment e slight

Table 6 Variation in average UTS YS El and Q values of thealloys studied in as-cast and T5- and T6-treated conditions ob-tained at 250degC

Alloy Condition UTS(MPa)

YS(MPa) El Q (Equation (1))

M1SAs-cast 16995 15756 367 25465T5 17207 16151 202 21791T6 21765 21365 192 26014

M2SAs-cast 18632 17284 225 23915T5 19625 17885 160 22671T6 22372 22233 215 27365

M3SAs-cast 17576 16284 285 24399T5 18107 17745 161 21216T6 24874 24562 154 27668

M4SAs-cast 18053 16735 177 21757T5 18186 17913 132 19985T6 25358 25332 106 25735

M5SAs-cast 17648 16232 245 23492T5 19110 18402 176 22786T6 22209 22055 132 23996

12 Advances in Materials Science and Engineering

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

CorrosionInternational Journal of

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ate

ria

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Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

(i) (j)

Figure 1 Backscattered electron images for as-cast (left) and solution heat-treated (right) conditions of the alloys studied (a b) M1S (basealloy) (c d) M2S (2wt Ni) (e f ) M3S (075wt Mn) (g h) M4S (4wt Ni) and (i j) M5S (2wt Ni + 075 wt Mn)

(a) (b)

(c) (d)

(e) (f )

Figure 2 Continued

Advances in Materials Science and Engineering 5

micrographs to a certain extent e existence of thesepartially modified silicon particles could be a result of thehigh Mg content sim06 wt of the alloys It has been re-ported by Joenoes and Gruzleski [29] and Dunn and Dickert[30] that the presence of Mg and copper can change themicrostructure from a fully modified structure into a par-tially modified one due to the formation ofMg2Sr(Si Al) andAl-Cu-Sr phases which will result in reducing the amount ofavailable strontium (Sr) to achieve the required degree ofmodification of the eutectic silicon particles In the present

case however since the contents of Sr Cu and Mg are keptconstant in the alloys investigated other explanations aremandatory to explain the variations in the modification levelof the eutectic Si particles in these alloys

As per the micrographs shown in Figures 2(e) and 2(g)alloys M3S (354 + 002wt Sr + 03 wt Zr + 075wtMn) and M4S (354 + 002wt Sr + 03 wt Zr + 4wt Ni)appear to contain less amounts of partially modified eutecticsilicon is observation can be ascribed to the existingphases in the microstructure of the two alloys which may

(g) (h)

(i) (j)

Figure 2 Optical micrographs at 500X showing the morphology of the eutectic silicon in the alloys studied (left) as-cast conditions and(right) solution heat-treated conditions (a) as-cast alloy M1S (b) SHTalloy M1S (c) as-cast alloy M2S (d) SHTalloy M2S (e) as-cast alloyM3S (f ) SHT alloy M3S (g) as-cast alloy M4S (h) SHT alloy M4S (i) as-cast alloy M5S and (j) SHT alloy M5S

Table 4 Characteristics of eutectic silicon particles in as-cast and solution heat-treated conditions of the alloys studied

Alloy code and conditionParticle area

(μm2)Particle length

(μm) Aspect ratio Roundness () Sphericity ()

Av SD Av SD Av SD Av SD Av SDM1S-AC 285 439 267 248 196 133 049 021 075 028M1S-SHT 371 471 260 210 171 149 058 019 085 021M2S-AC 353 760 283 329 196 244 050 023 074 030M2S-SHT 567 808 327 295 179 127 056 020 081 023M3S-AC 192 310 214 222 192 243 051 022 077 028M3S-SHT 535 604 312 232 169 292 061 017 086 019M4S-AC 311 661 265 330 202 358 050 025 073 032M4S-SHT 399 553 268 243 186 265 056 022 082 023M5S-AC 387 688 312 343 212 627 048 022 070 030M5S-SHT 570 744 352 320 195 360 054 020 078 025

6 Advances in Materials Science and Engineering

contribute to variations in the free content of silicon andorstrontium Such variations may lead to a more efficientmodification in the case of a lower SiSr ratio and vice versa

On one hand a high amount of the copper in alloy M4S(containing 4 Ni) is consumed in forming Al3NiCu phase[11] and thus the possibility of forming the Al-Cu-Sr phasereported by Joenoes and Gruzleski [29] will be reducedConsequently more Sr will not be consumed to form the Al-Cu-Sr phase and thus better modification would be ex-pected for Ni-containing alloys particularly those withhigher Ni-content as in alloy M4S On the other hand theaddition of 075 wt Mn in alloy M3S changes some of theβ-Al5FeSi iron phase into Chinese script-like α-Al15(FeMn)3Si2 phase and sludge particles e mutual existence ofthe two Fe-based phases ie β-Al5FeSi and α-Al15(FeMn)3Si2 will lower the silicon content (ie reduce the Siphase) in alloy M3S to an extent which will allow a bettermodification level compared to that attained for the rest ofthe alloys studied as depicted in Figure 2(e)

ermal modification is yet another effective way toalter the morphology of eutectic silicon particles It isevident from the micrographs shown in Figure 2 on theright that the solution treatment changes the fibrousinterconnected eutectic silicon particles detected in the as-cast condition into globular particles with rounded edgese evolution of the morphology of the eutectic siliconparticles from fibrous to globular in these alloys is a directresult to the combined effect of solution-heat treatment andstrontium modification as previously stated by Chen et al[31] and Yuying et al [32]

It is evident from the data presented in Table 4 that theaverage Si particle area increases after solution treatment at495degC for 5 hours for all the alloys Additionally the sol-utionizing treatment produces a noticeable improvement inthe spheroidization of the Si particles concomitant withenhancements in the roundness values as can be seenqualitatively from the micrographs shown in Figure 2 eincrease in sphericity and roundness values would producea corresponding decrease in the aspect ratio as seen inTable 4

32 Mechanical Performance

321 Ambient-Temperature Tensile Testing In the presentstudy the sole addition of sim03 wt Zr to the 354-type Al-Si-Cu-Mg cast alloy (ie the base alloy M1S) in the as-castcondition enhances the ambient-temperature strengthvalues of the Zr-free 354 alloy (alloy A) used in previousinvestigations in the same group by Hernandez-Sandoval[16] by sim26MPa (UTS) and 40MPa (YS) respectivelyese enhancements in the strength values are accompaniedby a limited reduction in the alloy ductility (sim0054) Forthe solution heat-treated condition on the other hand theUTS and ductility values of the base alloy M1S remainvirtually constant at sim300MPa and sim63 respectivelywhile the yield strength increases by sim33MPa compared toalloy A in the work of Hernandez-Sandoval [16] e im-proved strength values of Zr-containing Al-Si-Cu-Mg alloy

emphasize the role of Zr addition in enhancing the ambient-temperature tensile properties

Figure 3 shows the ambient-temperature tensile prop-erties obtained for the alloys under investigation In the as-cast condition the base alloy M1S (354 + 03 wt Zr) showsthe lowest UTS and YS values As-cast strength values of theother alloys ie M2S through M5S show enhancements of14ndash25 and 16ndash26 in UTS and YS respectively comparedto the base alloy (M1S) However the ductility values ofalloys M2S through M5S show inconsistent variations withrespect to the ductility of the base alloy M1S these variationscomprise enhancements in case of alloy M3S deteriorationsin the case of alloys M4S and M5S and almost unchangedductility value in the case of alloy M2S

e probable explanations for the enhanced strengthvalues of alloy M3S are the formation of favorable phaseswhich are advantageous to the strength values and thehighly refined as-cast Si particles (Table 4) as a result to theaddition of 075 wt Mn to the base alloy (M1S) It is wellestablished that the addition of Mn neutralizes to someextent the deleterious effect of iron impurities by trans-forming the detrimental needle-like β-Al5FeSi phase into theless harmful α-Al15(Fe Mn)3Si2 phase which appears ineither script-like form or as blocky sludge particles or bothWhile there is no doubt about the positive effect of thescript-like α-phase on strength and ductility values there ismuch debate however on the effect of the sludge particleson the tensile properties either they are harmful as regularlybelieved [28 33 34] or favorable to the tensile properties[7 35 36] Garza-Elizondo [7] has reported that the presenceof these hard particles in the soft α-Al matrix may contributein enhancing the tensile properties through the developmentof more uniformly distributed stresses within the matrix

For the Ni-containing alloys enhancements in thestrength values can be correlated to the formation of Ni-containing intermetallic compounds such as Al9FeNiAl3CuNi and Al3Ni which can hinder the propagation ofcracks similar findings are reported in previous studies[11 16] Increasing the Ni content from 2wt to 4wtinversely affects the tensile properties at room temperatureIt is believed that the precipitation of higher volume frac-tions of the acicular Al9FeNi and Al3CuNi phases in the as-cast alloy M4S (4wt Ni) is responsible for the de-terioration of the tensile properties at room temperature

Apparently from Figure 3 the base alloy M1S proves tobe very responsive to solution heat treatment because itshows an increase of 40MPa and 8MPa in the as-cast UTSand YS values respectively after solutionizing at 495degC for 5hours In addition the ductility of the solutionizedM1S alloyalso shows an increase of sim5 over the ductility valueobtained for the as-cast condition On the other hand theother alloys ie M2S through M5S show small improve-ments in the range of 2ndash10MPa for UTS values anda noticeable reduction in YS values (18ndash36MPa) comparedto their strength values in the as-cast conditione ductilityvalues of alloys M2S through M5S increase after solutiontreatment e enhanced ductility values after solution heattreatment in particular are related to the changes in theeutectic silicon morphology Coarse acicular silicon particles

Advances in Materials Science and Engineering 7

serve as crack initiators which is the case in the as-castcondition whereas more spherical Si particles with roundededges and decreased aspect ratios are obtained in the so-lution heat-treated case

Figures 3(a) and 3(b) show that the strength values of thebase alloy M1S are 289MPa (UTS)259MPa (YS) and342MPa (UTS)325MPa (YS) in the T5- and T6-treatedconditions respectively Alloys M2S and M3S exhibit thehighest strength among the alloys studied with values of300MPa (UTS)277MPa (YS) and 315MPa (UTS)279MPa(YS) respectively in the T5-treated condition and 362MPa(UTS)352MPa (YS) and 357MPa (UTS)355MPa (YS) inthe T6-treated condition respectively e strength values(UTS and YS) of alloys M1S M2S (M1S+ 2wt Ni) andM3S (M1S+075wtMn) show distinct enhancements afterapplying the T6 treatment in comparison to the as-cast andas-solutionized conditions In contrast alloys M4S (M1S+4wt Ni) and M5S (M1S+2wt Ni+075wt Mn)exhibit a very limited enhancement in UTS (sim15MPa) after T6heat treatment with reference to their strength in the as-castand as-quenched conditions Additionally from Figure 3(c) itcan be seen that the ductility values reduce considerably afterT6 treatment when compared to the as-cast ductility values ofthe respective alloys Ductility values of the alloys studied arelimited in general due to the high silicon content sim9wt andthe presence of both Mg and Cu [30]

e enhanced strength values of alloy M2S particularlyfor the T6-treated condition can be attributed to thepresence of Ni-containing phases such as Al3Ni Al9FeNiand Al3CuNi in addition to the ne precipitates formedafter applying T6 treatment [37 38] With respect to alloyM3S the improved strength values following T5- and T6-heat treatments can be ascribed to (i) the presence ofα-Al15(Fe Mn)3Si2 in the form of blocky hard particles (ii)the precipitated strengthening Cu- and Mg-containingdispersoids and (iii) the probable formation of Al6Mnne dispersoids in the presence of a high Mn content of075 wt [39 40] e presence of these Mn dispersoidssignicantly improves the yield and ultimate strength valueswithout sacricing the ductility [39 41 42]

e presence of a high nickel content in T6-treated alloyM4S (4wt) results in deteriorating the ambient-temperature tensile properties as can be inferred fromFigure 3 similar observations have been noted by otherauthors [71043ndash46] is deterioration in the strengthvalues is a direct result of the high content of Ni which inturn will consume some of the available copper in the alloyto form the detected Al3CuNi phase As a result this willreduce the amount of copper available for strengtheningthrough precipitation hardening during heat treatment [10]Furthermore the precipitation of Al9FeNi and Al3CuNiphases in high volume fractions (Table 3) would facilitate

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(a)

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(b)

01234567

AC SHT T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

M1SM2SM3S

M4SM5S

(c)

Figure 3 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in as-cast solution heat-treated (SHT) and T5- andT6-treated conditions obtained at ambient temperature

8 Advances in Materials Science and Engineering

cracking since they would act as stress raisers causinginstability in the flow strain and hence the ductility of thisalloy will reduce accordingly

In general the room-temperature tensile properties inthe T6 heat-treated conditions are better than those obtainedwith the T5 treatment for the alloys studied e use ofpermanent mold casting which is the technique used forproducing the test bars would preserve copper and mag-nesium in considerable amounts in solid solution due to thehigh solidification rate us by applying artificial agingdirectly after solidification (ie T5 temper) large pro-portions of the dissolved Cu andMg in the solid solution willform strengthening dispersoids e T6 heat treatment onthe other hand involves solutionizing the as-cast structure ata sufficiently high temperature in order to dissolve higheramounts of Cu and Mg in solid solution in order to forma supersaturated solid solution upon quenching and toachieve further modification of the eutectic Si particlesus the artificial aging in the case of T6 treatment willprecipitate fine strengthening particles in larger proportionsthan in the case of T5 treatment which will enhance the alloystrength to a greater extent however at the expense ofductility

For the alloys studied the ambient-temperature tensiletesting data are listed in Table 5 along with the quality indexvalues which were calculated using Equations (1) and (2)according to the models developed by Drouzy et al [47] andCaceres [48] respectively

Q SUTS + dlog ef 1113857 (1)

Qc K (qn)n expminusqn + 04 log(100qn)1113858 1113859 (2)

where Q and Qc (MPa) are the quality indices according toDrouzy and Caceres models SUTS refers to the ultimatetensile strength (MPa) ef refers to the percentage elongationto fracture d is a material constant equal to 150MPaK is thestrength coefficient (MPa) relative quality index (q) and n isthe strain-hardening exponent

Figure 4 shows the quality chart for the alloys studiedbased on Drouzy [47] model and depicts variations in thequality index values based on the chemical composition andthe applied heat treatment Equations (1) and (3) were usedto develop the ldquoiso-Qrdquo and ldquoiso-YSrdquo lines in the chart

Sp(ys) aSUTS minus blog ef 1113857 + C (3)

where coefficients a b and c were quantified as 1 60MPaand minus13MPa respectively

e quality index values Q and Qc listed in Table 5 showthe same trend in variations however with different valuese difference between Q and Qc increases in the T5 and T6heat-treated conditions which can be accredited to the factthat the alloy quality is affected by the net amount by whichthe increase in strength is balanced by the reduction inductility As can be seen from Table 5 and Figure 4 the bestquality values for the alloys are obtained after solution heattreatment attributed to the microstructural changes thattake place during the solution treatment including thedissolution of strengthening elements the homogenization

of the segregated as-cast structure and the spheroidizationof the eutectic silicon particles ese changes will signifi-cantly enhance the alloy ductility in addition to a limitedenhancement in UTS values Consequently the quality in-dex values of the as-quenched (or solution heat-treated)alloys are remarkably higher than those in the as-castcondition

While the T6 heat treatment improves the UTS valuesconsiderably in comparison to the UTS values obtainedafter solution treatment it does so at the expense of theductility is trade-off between UTS and ductility valueswill certainly affect the quality index values and not nec-essarily in a positive way Likewise a similar behavior isnoted for the T5-treated alloys as well as can be inferredfrom Figure 4

It is evident that the superior ductility of the base alloyM1S is the main reason for the improved quality indices ofthis alloy in the majority of the conditions studied On theother hand the mutual enhancement in the strength andductility values of alloys M2S and M3S compared to those ofalloys M4S and M5S is responsible for the higher qualityindices of the former compared to those of the latter

e addition of Mn in alloy M3S results in transformingthe needles of the β-iron phase into the less detrimentalα-iron phase this favorable morphological change is be-lieved to improve the ductility and strength values of alloyM3S Whereas the structure of alloy M2S contains Ni-bearing phases with acicular morphologies and β-ironneedles that negatively affect the mechanical propertiesAccordingly the quality index values of alloy M3S are higherthan those of the 2wt Ni-containing alloy M2S in the as-cast SHT and T5 conditions In contrast the quality indexvalues of the T6-treated alloysM2S andM3S show a reversedbehavior according to the marginal variations in their tensileproperties and hence the quality index values

From Table 5 it is observable that the quality indexvalues calculated using Drouzyrsquos approach are higher thanthose obtained by the model developed by Caceres for alltreatment conditions per each alloy except for solution-treated conditions is can be attributed to the improvedductility of as-quenched conditions that will allow moreaccurate determination of the material parameters (K andn) us it would be advisable to calculate the quality indexvalues of solution-treated conditions using Caceresrsquo modelespecially for materials with low ductility at roomtemperature

322 Elevated-Temperature Tensile Testing Figure 5 revealsthe elevated-temperature tensile properties obtained at250degC for the alloys studied By tensile testing at 250degC allthe investigated alloys endure some softening owing to thepossible coarsening of the strengthening precipitates thatexist during tensile testing at room temperature (Figure 3)Figures 5(a) and 5(b) demonstrate that additions of Ni andMn in different amounts and combinations to the base alloyie alloys M2S through M5S slightly improve the strengthvalues of the base alloy in the range of 5ndash15MPa for both as-cast and T5-treated conditions e tight enhancement in

Advances in Materials Science and Engineering 9

strength values of the T5-treated conditions can be ascribed tothe limited variations in themicrostructural features of as-caststructures as well as to the low proportion of strengtheningprecipitates in the structure of T5-treated alloys

In regard to the ductility values in the as-cast conditionFigure 5(c) reveals that the highest ductility value is observedto be associated with the base alloy M1S with a value of

sim36 followed by the ductility of the Mn-containing alloysM3S andM5S and ending up with the lowest ductility valuesfor alloys M2S and M4S containing 2 and 4wt Ni re-spectively e higher ductility values of the as-cast Mn-containing alloys M3S andM5S can be attributed to the well-refined Si particles Table 4 and the transformation ofa considerable amount of β-Al5FeSi needles which may act

Table 5 Variation in average UTS YS El Qc and Q values of the alloys studied in as-cast SHT and T5- and T6-treated conditionsobtained at ambient temperature

Alloy Condition UTS(MPa)

YS(MPa)

Totalstrain ()

Plasticstrain () E (GPa) n K q Qc

(Equation (2))Q

(Equation (1))Difference

(QminusQc) (MPa)

M1S

As-cast 26086 19439 158 116 6266 018 58056 007 27788 29050 1262SHT 30034 20251 622 574 6250 017 57926 034 51236 41943 minus9293T5 28950 25875 094 048 6306 013 59169 004 21706 28543 6838T6 34195 32499 11075 056 6245 010 57691 006 28153 34860 6707

M2S

As-cast 32035 23585 163 116 6758 019 76378 006 34214 35219 1005SHT 32774 21261 320 270 6623 017 75932 016 53109 40343 minus12766T5 29997 27719 080 034 6564 015 70196 002 16710 28522 11812T6 36233 35157 080 024 6471 011 70779 002 19604 34816 15212

M3S

As-cast 32578 24572 176 126 6473 015 64889 008 35471 36255 784SHT 33475 20943 381 330 6447 012 64647 027 54926 42197 minus12729T5 31458 27939 098 049 6414 013 63449 004 23821 31310 7489T6 35701 35514 075 020 6432 008 62421 002 19202 33850 14648

M4S

As-cast 30440 22461 133 087 6610 020 83677 004 29364 32287 2923SHT 31232 20709 222 175 6656 018 82135 010 46959 36427 minus10532T5 27644 25414 071 031 6843 020 85707 002 9928 25451 15524T6 31598 31598 05705 011 6710 010 63474 001 7752 27941 20189

M5S

As-cast 29707 22659 127 083 6691 020 79201 004 27391 31280 3889SHT 29979 20664 199 154 6735 017 78035 009 43714 34462 minus9252T5 28461 27700 066 022 6474 015 72211 001 9720 25745 16025T6 31404 31404 056 011 6789 011 67764 001 4543 27632 23089

1

23

12

3

1 2

3

12

3

1 23

250

300

350

400

05 5

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

Drouzy quality index chart room temperature

M1SM2SM3S

M4SM5S

4 4

44

YS = 350 MPa

Q = 500 MPaQ = 450 MPa

Q = 350 MPa

Q = 250 MPa

Q = 300 MPa

Q = 400 MPa

YS = 250 MPa

4

1 as-cast2 SHT3 T54 T6

Figure 4 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast SHT and T5- and T6-treated conditions obtained at ambient temperature

10 Advances in Materials Science and Engineering

as crack initiators into the less detrimental α-Al15(MnFe)3Si2 phase with script-like andor sludge morphologies

e addition of Ni on the other hand lowers theductility values even for alloy M5S that contains 075wtMn when compared to alloy M3S which is Ni-free ereduction in ductility values of the as-cast Ni-containingalloys can be directly correlated to the presence of acicularNi-bearing phases with sharp edges such as Al3Ni Al9FeNiand Al3CuNi phases Variation in chemical compositionshas a limited eiexclect on the ductility values obtained at 250degCfor the T5-treated alloys since the maximum absolutediiexclerence in the ductility values of alloys M2S through M5Sis found to be sim044 Application of T5 and T6 heattreatments reduces the ductility observed in the as-castcondition e ductility values in the T6-treated conditionare generally lower than those obtained with T5 treatmentconditions

e application of the T6 heat treatment enhances thestrength values of as-cast conditions regardless the alloycomposition as shown in Figures 5(a) and 5(b) e en-hanced strength values of alloy M4S after T6 heat treatmentmay be attributed to the presence of δ-Al3CuNi and eutecticAl-Al3Ni phases that prove to contribute eiexclectively to theelevated-temperature strength of alloy M4S in spite ofa considerable amount of Cu that is consumed in formingthe δ-Al3CuNi phase which will certainly aiexclect the amount

of ne Al2Cu dispersoids formed which is consistent withthe ndings reported in references [38 49]

Interestingly alloys M3S (354 + 075wt Mn) and M4S(354 + 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the diiexclerent conditions ex-amined Moreover alloy M3S is considered to be morefavorable between the two since it exhibits higher ductilitythan that of the Ni-containing alloy M4S ese two alloysexhibit the best strength values (UTS and YS) in the T6-treated conditions among the investigated alloys whereasthe strength values of the other three alloys ie alloys M1SM2S and M5S are close to each other and lower than thestrength values obtained for alloys M3S and M4S bysim36MPa is observation would emphasize the advanta-geous role of adding Mn instead of Ni to enhance theelevated-temperature tensile properties along with its eco-nomic impact

Generally the closeness of the elevated-temperaturestrength values of the alloys studied can be credited tothe presence of 03 wt Zr in each alloy whereby theformation of the ne metastable L12-Al3Zr particles is ex-pected in the microstructures of all the alloys which in turnwill improve the alloy strength in a common manner

For elevated-temperature tensile properties the conceptof the quality index will be discussed according to theconcept of Drouzy et al [47] (Q) Table 6 demonstrates the

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditionsM1SM2SM3S

M4SM5S

(a)

M1SM2SM3S

M4SM5S

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditions

(b)

M1SM2SM3S

M4SM5S

005

115

225

335

445

AC T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

(c)

Figure 5 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in the as-cast solution heat-treated (SHT) and T5-and T6-treated conditions obtained at 250degC

Advances in Materials Science and Engineering 11

elevated-temperature tensile data along with the quality indexvalues (Q) of the alloys studied calculated using Equation (1)Figure 6 shows the quality chart obtained based on the cal-culations of Drouzy et al [47] As may be seen the qualityindex values obtained at 250degC do not show wide variation invalues as was observed in the case of the ambient-temperature data is limited variation can be understoodin light of the balanced variation in UTS and ductility valuesobtained at the elevated temperature of 250degC For examplethe base alloyM1S in the as-cast condition exhibits the highestductility value of 367 and a UTS value of 16995MPa whilethe lowest ductility is experienced by alloy M4S for the T6-treated condition with a value of 106 along with a UTSvalue of 25358MPa By calculating the quality indices of thesetwo conditions they revealQ values of 26395 and 25735MPafor as-cast M1S and T6-treated M4S respectively ose twoextreme conditions show that despite the considerable vari-ation in the UTS values on the one hand and ductility valueson the other for these two conditions the quality indices inboth cases remain almost unchanged due to the balancedtrade-off between the UTS and ductility values e relativelylowUTS and ductility values obtained at elevated temperature(250degC) for the T5-treated condition result in the T5-treatedalloys exhibiting minimum Q values among the conditionsstudied

Another interesting observation is that the quality indexvalues for alloys M2S and M3S in the T6-treated conditionare found to be the maximum for the alloys and conditionsstudied is observation highlights the enhanced charac-teristics of alloy M3S which contains 075wt Mn andemphasizes the positive influence of the high Mn-additionon the elevated-temperature tensile properties which arefound to be more or less comparable to those obtained withthe addition of 2 and 4wt Ni to the same base alloy

e favorable role of the blocky α-Al15(Fe Mn)3Si2phase termed as sludge particles in improving the tensileproperties of alloy M3S at 25degC and 250degC can be witnessed

from the fractograph of alloy M3S after testing at 250degCpresented in Figure 7 e sludge particles appear to retardthe propagation of the cracks developed in the other phaseswhich will subsequently enhance the mechanical propertiesof the respective alloy Yet another interesting observationmade from this figure is that while many of the intermetallicphase particles appear cracked as indicated by the solidarrows the sludge particles however are crack-freeWhereas the multiple cracked Ni-rich phases exist on thefracture surface of alloy M2S after testing at 250degC are be-lieved to contribute to the crack initiation process and hencedeteriorate the tensile properties of this alloy as witnessed inFigure 8

323 Hardness Values Figure 9 illustrates the variation inthe hardness values of the alloys as a function of the appliedheat treatment At first glance one can observe from Figure 9that the hardness values of different alloys show insignificantvariations for the same conditions For each alloy the peak-aged condition exhibits the highest hardness value among allconditions Also the tailored alloys ie M2S through M5Sshow better hardness values than those obtained for the basealloy in all the conditions studied

Variations in hardness values of the alloys in the as-castcondition can be attributed to the additions of Ni andor Mnmade to the base alloy M1S It was seen that additions of Niandor Mn in various amounts increased the volume frac-tions of intermetallic compounds considerably as listed inTable 3 e variations in hardness values follow the sametrend as variations in the percentage volume fraction ofintermetallic compounds us the base alloy M1S exhibitsthe lowest hardness value in the as-cast condition having thelowest volume fraction according to Table 3 and the highesthardness value of the same condition is associated with alloyM4S that has the highest volume fraction of intermetalliccompounds is observation highlights the effective role ofintermetallic compounds in enhancing the hardness values[19 50]

e dissolution of the strengthening elements over thecourse of the solution treatment reduces the hardness valuesin spite of the expected improved homogeneity in com-position and evolution of the eutectic silicon morphologyfollowing solution treatment is behavior emphasizes thecrucial role of intermetallic phases in influencing the me-chanical performance of alloys It is established that thehardness value of a specific alloy corresponds to the com-bination of the tensile yield strength and work-hardeningrate of the alloy [50 51] e order of the alloys studiedaccording to the hardness value in the as-quenched con-dition matches to a large extent their order with respect totheir yield strength in the same as-quenched condition(Figure 3)

Direct artificial aging following casting of test barsie T5-temper treatment introduces slight improvements inthe hardness values with respect to those obtained for the as-cast condition is can be attributed to the limited changesin the microstructure of the as-cast alloysbars followingdirect artificial aging without solution treatment e slight

Table 6 Variation in average UTS YS El and Q values of thealloys studied in as-cast and T5- and T6-treated conditions ob-tained at 250degC

Alloy Condition UTS(MPa)

YS(MPa) El Q (Equation (1))

M1SAs-cast 16995 15756 367 25465T5 17207 16151 202 21791T6 21765 21365 192 26014

M2SAs-cast 18632 17284 225 23915T5 19625 17885 160 22671T6 22372 22233 215 27365

M3SAs-cast 17576 16284 285 24399T5 18107 17745 161 21216T6 24874 24562 154 27668

M4SAs-cast 18053 16735 177 21757T5 18186 17913 132 19985T6 25358 25332 106 25735

M5SAs-cast 17648 16232 245 23492T5 19110 18402 176 22786T6 22209 22055 132 23996

12 Advances in Materials Science and Engineering

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

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micrographs to a certain extent e existence of thesepartially modified silicon particles could be a result of thehigh Mg content sim06 wt of the alloys It has been re-ported by Joenoes and Gruzleski [29] and Dunn and Dickert[30] that the presence of Mg and copper can change themicrostructure from a fully modified structure into a par-tially modified one due to the formation ofMg2Sr(Si Al) andAl-Cu-Sr phases which will result in reducing the amount ofavailable strontium (Sr) to achieve the required degree ofmodification of the eutectic silicon particles In the present

case however since the contents of Sr Cu and Mg are keptconstant in the alloys investigated other explanations aremandatory to explain the variations in the modification levelof the eutectic Si particles in these alloys

As per the micrographs shown in Figures 2(e) and 2(g)alloys M3S (354 + 002wt Sr + 03 wt Zr + 075wtMn) and M4S (354 + 002wt Sr + 03 wt Zr + 4wt Ni)appear to contain less amounts of partially modified eutecticsilicon is observation can be ascribed to the existingphases in the microstructure of the two alloys which may

(g) (h)

(i) (j)

Figure 2 Optical micrographs at 500X showing the morphology of the eutectic silicon in the alloys studied (left) as-cast conditions and(right) solution heat-treated conditions (a) as-cast alloy M1S (b) SHTalloy M1S (c) as-cast alloy M2S (d) SHTalloy M2S (e) as-cast alloyM3S (f ) SHT alloy M3S (g) as-cast alloy M4S (h) SHT alloy M4S (i) as-cast alloy M5S and (j) SHT alloy M5S

Table 4 Characteristics of eutectic silicon particles in as-cast and solution heat-treated conditions of the alloys studied

Alloy code and conditionParticle area

(μm2)Particle length

(μm) Aspect ratio Roundness () Sphericity ()

Av SD Av SD Av SD Av SD Av SDM1S-AC 285 439 267 248 196 133 049 021 075 028M1S-SHT 371 471 260 210 171 149 058 019 085 021M2S-AC 353 760 283 329 196 244 050 023 074 030M2S-SHT 567 808 327 295 179 127 056 020 081 023M3S-AC 192 310 214 222 192 243 051 022 077 028M3S-SHT 535 604 312 232 169 292 061 017 086 019M4S-AC 311 661 265 330 202 358 050 025 073 032M4S-SHT 399 553 268 243 186 265 056 022 082 023M5S-AC 387 688 312 343 212 627 048 022 070 030M5S-SHT 570 744 352 320 195 360 054 020 078 025

6 Advances in Materials Science and Engineering

contribute to variations in the free content of silicon andorstrontium Such variations may lead to a more efficientmodification in the case of a lower SiSr ratio and vice versa

On one hand a high amount of the copper in alloy M4S(containing 4 Ni) is consumed in forming Al3NiCu phase[11] and thus the possibility of forming the Al-Cu-Sr phasereported by Joenoes and Gruzleski [29] will be reducedConsequently more Sr will not be consumed to form the Al-Cu-Sr phase and thus better modification would be ex-pected for Ni-containing alloys particularly those withhigher Ni-content as in alloy M4S On the other hand theaddition of 075 wt Mn in alloy M3S changes some of theβ-Al5FeSi iron phase into Chinese script-like α-Al15(FeMn)3Si2 phase and sludge particles e mutual existence ofthe two Fe-based phases ie β-Al5FeSi and α-Al15(FeMn)3Si2 will lower the silicon content (ie reduce the Siphase) in alloy M3S to an extent which will allow a bettermodification level compared to that attained for the rest ofthe alloys studied as depicted in Figure 2(e)

ermal modification is yet another effective way toalter the morphology of eutectic silicon particles It isevident from the micrographs shown in Figure 2 on theright that the solution treatment changes the fibrousinterconnected eutectic silicon particles detected in the as-cast condition into globular particles with rounded edgese evolution of the morphology of the eutectic siliconparticles from fibrous to globular in these alloys is a directresult to the combined effect of solution-heat treatment andstrontium modification as previously stated by Chen et al[31] and Yuying et al [32]

It is evident from the data presented in Table 4 that theaverage Si particle area increases after solution treatment at495degC for 5 hours for all the alloys Additionally the sol-utionizing treatment produces a noticeable improvement inthe spheroidization of the Si particles concomitant withenhancements in the roundness values as can be seenqualitatively from the micrographs shown in Figure 2 eincrease in sphericity and roundness values would producea corresponding decrease in the aspect ratio as seen inTable 4

32 Mechanical Performance

321 Ambient-Temperature Tensile Testing In the presentstudy the sole addition of sim03 wt Zr to the 354-type Al-Si-Cu-Mg cast alloy (ie the base alloy M1S) in the as-castcondition enhances the ambient-temperature strengthvalues of the Zr-free 354 alloy (alloy A) used in previousinvestigations in the same group by Hernandez-Sandoval[16] by sim26MPa (UTS) and 40MPa (YS) respectivelyese enhancements in the strength values are accompaniedby a limited reduction in the alloy ductility (sim0054) Forthe solution heat-treated condition on the other hand theUTS and ductility values of the base alloy M1S remainvirtually constant at sim300MPa and sim63 respectivelywhile the yield strength increases by sim33MPa compared toalloy A in the work of Hernandez-Sandoval [16] e im-proved strength values of Zr-containing Al-Si-Cu-Mg alloy

emphasize the role of Zr addition in enhancing the ambient-temperature tensile properties

Figure 3 shows the ambient-temperature tensile prop-erties obtained for the alloys under investigation In the as-cast condition the base alloy M1S (354 + 03 wt Zr) showsthe lowest UTS and YS values As-cast strength values of theother alloys ie M2S through M5S show enhancements of14ndash25 and 16ndash26 in UTS and YS respectively comparedto the base alloy (M1S) However the ductility values ofalloys M2S through M5S show inconsistent variations withrespect to the ductility of the base alloy M1S these variationscomprise enhancements in case of alloy M3S deteriorationsin the case of alloys M4S and M5S and almost unchangedductility value in the case of alloy M2S

e probable explanations for the enhanced strengthvalues of alloy M3S are the formation of favorable phaseswhich are advantageous to the strength values and thehighly refined as-cast Si particles (Table 4) as a result to theaddition of 075 wt Mn to the base alloy (M1S) It is wellestablished that the addition of Mn neutralizes to someextent the deleterious effect of iron impurities by trans-forming the detrimental needle-like β-Al5FeSi phase into theless harmful α-Al15(Fe Mn)3Si2 phase which appears ineither script-like form or as blocky sludge particles or bothWhile there is no doubt about the positive effect of thescript-like α-phase on strength and ductility values there ismuch debate however on the effect of the sludge particleson the tensile properties either they are harmful as regularlybelieved [28 33 34] or favorable to the tensile properties[7 35 36] Garza-Elizondo [7] has reported that the presenceof these hard particles in the soft α-Al matrix may contributein enhancing the tensile properties through the developmentof more uniformly distributed stresses within the matrix

For the Ni-containing alloys enhancements in thestrength values can be correlated to the formation of Ni-containing intermetallic compounds such as Al9FeNiAl3CuNi and Al3Ni which can hinder the propagation ofcracks similar findings are reported in previous studies[11 16] Increasing the Ni content from 2wt to 4wtinversely affects the tensile properties at room temperatureIt is believed that the precipitation of higher volume frac-tions of the acicular Al9FeNi and Al3CuNi phases in the as-cast alloy M4S (4wt Ni) is responsible for the de-terioration of the tensile properties at room temperature

Apparently from Figure 3 the base alloy M1S proves tobe very responsive to solution heat treatment because itshows an increase of 40MPa and 8MPa in the as-cast UTSand YS values respectively after solutionizing at 495degC for 5hours In addition the ductility of the solutionizedM1S alloyalso shows an increase of sim5 over the ductility valueobtained for the as-cast condition On the other hand theother alloys ie M2S through M5S show small improve-ments in the range of 2ndash10MPa for UTS values anda noticeable reduction in YS values (18ndash36MPa) comparedto their strength values in the as-cast conditione ductilityvalues of alloys M2S through M5S increase after solutiontreatment e enhanced ductility values after solution heattreatment in particular are related to the changes in theeutectic silicon morphology Coarse acicular silicon particles

Advances in Materials Science and Engineering 7

serve as crack initiators which is the case in the as-castcondition whereas more spherical Si particles with roundededges and decreased aspect ratios are obtained in the so-lution heat-treated case

Figures 3(a) and 3(b) show that the strength values of thebase alloy M1S are 289MPa (UTS)259MPa (YS) and342MPa (UTS)325MPa (YS) in the T5- and T6-treatedconditions respectively Alloys M2S and M3S exhibit thehighest strength among the alloys studied with values of300MPa (UTS)277MPa (YS) and 315MPa (UTS)279MPa(YS) respectively in the T5-treated condition and 362MPa(UTS)352MPa (YS) and 357MPa (UTS)355MPa (YS) inthe T6-treated condition respectively e strength values(UTS and YS) of alloys M1S M2S (M1S+ 2wt Ni) andM3S (M1S+075wtMn) show distinct enhancements afterapplying the T6 treatment in comparison to the as-cast andas-solutionized conditions In contrast alloys M4S (M1S+4wt Ni) and M5S (M1S+2wt Ni+075wt Mn)exhibit a very limited enhancement in UTS (sim15MPa) after T6heat treatment with reference to their strength in the as-castand as-quenched conditions Additionally from Figure 3(c) itcan be seen that the ductility values reduce considerably afterT6 treatment when compared to the as-cast ductility values ofthe respective alloys Ductility values of the alloys studied arelimited in general due to the high silicon content sim9wt andthe presence of both Mg and Cu [30]

e enhanced strength values of alloy M2S particularlyfor the T6-treated condition can be attributed to thepresence of Ni-containing phases such as Al3Ni Al9FeNiand Al3CuNi in addition to the ne precipitates formedafter applying T6 treatment [37 38] With respect to alloyM3S the improved strength values following T5- and T6-heat treatments can be ascribed to (i) the presence ofα-Al15(Fe Mn)3Si2 in the form of blocky hard particles (ii)the precipitated strengthening Cu- and Mg-containingdispersoids and (iii) the probable formation of Al6Mnne dispersoids in the presence of a high Mn content of075 wt [39 40] e presence of these Mn dispersoidssignicantly improves the yield and ultimate strength valueswithout sacricing the ductility [39 41 42]

e presence of a high nickel content in T6-treated alloyM4S (4wt) results in deteriorating the ambient-temperature tensile properties as can be inferred fromFigure 3 similar observations have been noted by otherauthors [71043ndash46] is deterioration in the strengthvalues is a direct result of the high content of Ni which inturn will consume some of the available copper in the alloyto form the detected Al3CuNi phase As a result this willreduce the amount of copper available for strengtheningthrough precipitation hardening during heat treatment [10]Furthermore the precipitation of Al9FeNi and Al3CuNiphases in high volume fractions (Table 3) would facilitate

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(a)

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(b)

01234567

AC SHT T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

M1SM2SM3S

M4SM5S

(c)

Figure 3 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in as-cast solution heat-treated (SHT) and T5- andT6-treated conditions obtained at ambient temperature

8 Advances in Materials Science and Engineering

cracking since they would act as stress raisers causinginstability in the flow strain and hence the ductility of thisalloy will reduce accordingly

In general the room-temperature tensile properties inthe T6 heat-treated conditions are better than those obtainedwith the T5 treatment for the alloys studied e use ofpermanent mold casting which is the technique used forproducing the test bars would preserve copper and mag-nesium in considerable amounts in solid solution due to thehigh solidification rate us by applying artificial agingdirectly after solidification (ie T5 temper) large pro-portions of the dissolved Cu andMg in the solid solution willform strengthening dispersoids e T6 heat treatment onthe other hand involves solutionizing the as-cast structure ata sufficiently high temperature in order to dissolve higheramounts of Cu and Mg in solid solution in order to forma supersaturated solid solution upon quenching and toachieve further modification of the eutectic Si particlesus the artificial aging in the case of T6 treatment willprecipitate fine strengthening particles in larger proportionsthan in the case of T5 treatment which will enhance the alloystrength to a greater extent however at the expense ofductility

For the alloys studied the ambient-temperature tensiletesting data are listed in Table 5 along with the quality indexvalues which were calculated using Equations (1) and (2)according to the models developed by Drouzy et al [47] andCaceres [48] respectively

Q SUTS + dlog ef 1113857 (1)

Qc K (qn)n expminusqn + 04 log(100qn)1113858 1113859 (2)

where Q and Qc (MPa) are the quality indices according toDrouzy and Caceres models SUTS refers to the ultimatetensile strength (MPa) ef refers to the percentage elongationto fracture d is a material constant equal to 150MPaK is thestrength coefficient (MPa) relative quality index (q) and n isthe strain-hardening exponent

Figure 4 shows the quality chart for the alloys studiedbased on Drouzy [47] model and depicts variations in thequality index values based on the chemical composition andthe applied heat treatment Equations (1) and (3) were usedto develop the ldquoiso-Qrdquo and ldquoiso-YSrdquo lines in the chart

Sp(ys) aSUTS minus blog ef 1113857 + C (3)

where coefficients a b and c were quantified as 1 60MPaand minus13MPa respectively

e quality index values Q and Qc listed in Table 5 showthe same trend in variations however with different valuese difference between Q and Qc increases in the T5 and T6heat-treated conditions which can be accredited to the factthat the alloy quality is affected by the net amount by whichthe increase in strength is balanced by the reduction inductility As can be seen from Table 5 and Figure 4 the bestquality values for the alloys are obtained after solution heattreatment attributed to the microstructural changes thattake place during the solution treatment including thedissolution of strengthening elements the homogenization

of the segregated as-cast structure and the spheroidizationof the eutectic silicon particles ese changes will signifi-cantly enhance the alloy ductility in addition to a limitedenhancement in UTS values Consequently the quality in-dex values of the as-quenched (or solution heat-treated)alloys are remarkably higher than those in the as-castcondition

While the T6 heat treatment improves the UTS valuesconsiderably in comparison to the UTS values obtainedafter solution treatment it does so at the expense of theductility is trade-off between UTS and ductility valueswill certainly affect the quality index values and not nec-essarily in a positive way Likewise a similar behavior isnoted for the T5-treated alloys as well as can be inferredfrom Figure 4

It is evident that the superior ductility of the base alloyM1S is the main reason for the improved quality indices ofthis alloy in the majority of the conditions studied On theother hand the mutual enhancement in the strength andductility values of alloys M2S and M3S compared to those ofalloys M4S and M5S is responsible for the higher qualityindices of the former compared to those of the latter

e addition of Mn in alloy M3S results in transformingthe needles of the β-iron phase into the less detrimentalα-iron phase this favorable morphological change is be-lieved to improve the ductility and strength values of alloyM3S Whereas the structure of alloy M2S contains Ni-bearing phases with acicular morphologies and β-ironneedles that negatively affect the mechanical propertiesAccordingly the quality index values of alloy M3S are higherthan those of the 2wt Ni-containing alloy M2S in the as-cast SHT and T5 conditions In contrast the quality indexvalues of the T6-treated alloysM2S andM3S show a reversedbehavior according to the marginal variations in their tensileproperties and hence the quality index values

From Table 5 it is observable that the quality indexvalues calculated using Drouzyrsquos approach are higher thanthose obtained by the model developed by Caceres for alltreatment conditions per each alloy except for solution-treated conditions is can be attributed to the improvedductility of as-quenched conditions that will allow moreaccurate determination of the material parameters (K andn) us it would be advisable to calculate the quality indexvalues of solution-treated conditions using Caceresrsquo modelespecially for materials with low ductility at roomtemperature

322 Elevated-Temperature Tensile Testing Figure 5 revealsthe elevated-temperature tensile properties obtained at250degC for the alloys studied By tensile testing at 250degC allthe investigated alloys endure some softening owing to thepossible coarsening of the strengthening precipitates thatexist during tensile testing at room temperature (Figure 3)Figures 5(a) and 5(b) demonstrate that additions of Ni andMn in different amounts and combinations to the base alloyie alloys M2S through M5S slightly improve the strengthvalues of the base alloy in the range of 5ndash15MPa for both as-cast and T5-treated conditions e tight enhancement in

Advances in Materials Science and Engineering 9

strength values of the T5-treated conditions can be ascribed tothe limited variations in themicrostructural features of as-caststructures as well as to the low proportion of strengtheningprecipitates in the structure of T5-treated alloys

In regard to the ductility values in the as-cast conditionFigure 5(c) reveals that the highest ductility value is observedto be associated with the base alloy M1S with a value of

sim36 followed by the ductility of the Mn-containing alloysM3S andM5S and ending up with the lowest ductility valuesfor alloys M2S and M4S containing 2 and 4wt Ni re-spectively e higher ductility values of the as-cast Mn-containing alloys M3S andM5S can be attributed to the well-refined Si particles Table 4 and the transformation ofa considerable amount of β-Al5FeSi needles which may act

Table 5 Variation in average UTS YS El Qc and Q values of the alloys studied in as-cast SHT and T5- and T6-treated conditionsobtained at ambient temperature

Alloy Condition UTS(MPa)

YS(MPa)

Totalstrain ()

Plasticstrain () E (GPa) n K q Qc

(Equation (2))Q

(Equation (1))Difference

(QminusQc) (MPa)

M1S

As-cast 26086 19439 158 116 6266 018 58056 007 27788 29050 1262SHT 30034 20251 622 574 6250 017 57926 034 51236 41943 minus9293T5 28950 25875 094 048 6306 013 59169 004 21706 28543 6838T6 34195 32499 11075 056 6245 010 57691 006 28153 34860 6707

M2S

As-cast 32035 23585 163 116 6758 019 76378 006 34214 35219 1005SHT 32774 21261 320 270 6623 017 75932 016 53109 40343 minus12766T5 29997 27719 080 034 6564 015 70196 002 16710 28522 11812T6 36233 35157 080 024 6471 011 70779 002 19604 34816 15212

M3S

As-cast 32578 24572 176 126 6473 015 64889 008 35471 36255 784SHT 33475 20943 381 330 6447 012 64647 027 54926 42197 minus12729T5 31458 27939 098 049 6414 013 63449 004 23821 31310 7489T6 35701 35514 075 020 6432 008 62421 002 19202 33850 14648

M4S

As-cast 30440 22461 133 087 6610 020 83677 004 29364 32287 2923SHT 31232 20709 222 175 6656 018 82135 010 46959 36427 minus10532T5 27644 25414 071 031 6843 020 85707 002 9928 25451 15524T6 31598 31598 05705 011 6710 010 63474 001 7752 27941 20189

M5S

As-cast 29707 22659 127 083 6691 020 79201 004 27391 31280 3889SHT 29979 20664 199 154 6735 017 78035 009 43714 34462 minus9252T5 28461 27700 066 022 6474 015 72211 001 9720 25745 16025T6 31404 31404 056 011 6789 011 67764 001 4543 27632 23089

1

23

12

3

1 2

3

12

3

1 23

250

300

350

400

05 5

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

Drouzy quality index chart room temperature

M1SM2SM3S

M4SM5S

4 4

44

YS = 350 MPa

Q = 500 MPaQ = 450 MPa

Q = 350 MPa

Q = 250 MPa

Q = 300 MPa

Q = 400 MPa

YS = 250 MPa

4

1 as-cast2 SHT3 T54 T6

Figure 4 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast SHT and T5- and T6-treated conditions obtained at ambient temperature

10 Advances in Materials Science and Engineering

as crack initiators into the less detrimental α-Al15(MnFe)3Si2 phase with script-like andor sludge morphologies

e addition of Ni on the other hand lowers theductility values even for alloy M5S that contains 075wtMn when compared to alloy M3S which is Ni-free ereduction in ductility values of the as-cast Ni-containingalloys can be directly correlated to the presence of acicularNi-bearing phases with sharp edges such as Al3Ni Al9FeNiand Al3CuNi phases Variation in chemical compositionshas a limited eiexclect on the ductility values obtained at 250degCfor the T5-treated alloys since the maximum absolutediiexclerence in the ductility values of alloys M2S through M5Sis found to be sim044 Application of T5 and T6 heattreatments reduces the ductility observed in the as-castcondition e ductility values in the T6-treated conditionare generally lower than those obtained with T5 treatmentconditions

e application of the T6 heat treatment enhances thestrength values of as-cast conditions regardless the alloycomposition as shown in Figures 5(a) and 5(b) e en-hanced strength values of alloy M4S after T6 heat treatmentmay be attributed to the presence of δ-Al3CuNi and eutecticAl-Al3Ni phases that prove to contribute eiexclectively to theelevated-temperature strength of alloy M4S in spite ofa considerable amount of Cu that is consumed in formingthe δ-Al3CuNi phase which will certainly aiexclect the amount

of ne Al2Cu dispersoids formed which is consistent withthe ndings reported in references [38 49]

Interestingly alloys M3S (354 + 075wt Mn) and M4S(354 + 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the diiexclerent conditions ex-amined Moreover alloy M3S is considered to be morefavorable between the two since it exhibits higher ductilitythan that of the Ni-containing alloy M4S ese two alloysexhibit the best strength values (UTS and YS) in the T6-treated conditions among the investigated alloys whereasthe strength values of the other three alloys ie alloys M1SM2S and M5S are close to each other and lower than thestrength values obtained for alloys M3S and M4S bysim36MPa is observation would emphasize the advanta-geous role of adding Mn instead of Ni to enhance theelevated-temperature tensile properties along with its eco-nomic impact

Generally the closeness of the elevated-temperaturestrength values of the alloys studied can be credited tothe presence of 03 wt Zr in each alloy whereby theformation of the ne metastable L12-Al3Zr particles is ex-pected in the microstructures of all the alloys which in turnwill improve the alloy strength in a common manner

For elevated-temperature tensile properties the conceptof the quality index will be discussed according to theconcept of Drouzy et al [47] (Q) Table 6 demonstrates the

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditionsM1SM2SM3S

M4SM5S

(a)

M1SM2SM3S

M4SM5S

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditions

(b)

M1SM2SM3S

M4SM5S

005

115

225

335

445

AC T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

(c)

Figure 5 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in the as-cast solution heat-treated (SHT) and T5-and T6-treated conditions obtained at 250degC

Advances in Materials Science and Engineering 11

elevated-temperature tensile data along with the quality indexvalues (Q) of the alloys studied calculated using Equation (1)Figure 6 shows the quality chart obtained based on the cal-culations of Drouzy et al [47] As may be seen the qualityindex values obtained at 250degC do not show wide variation invalues as was observed in the case of the ambient-temperature data is limited variation can be understoodin light of the balanced variation in UTS and ductility valuesobtained at the elevated temperature of 250degC For examplethe base alloyM1S in the as-cast condition exhibits the highestductility value of 367 and a UTS value of 16995MPa whilethe lowest ductility is experienced by alloy M4S for the T6-treated condition with a value of 106 along with a UTSvalue of 25358MPa By calculating the quality indices of thesetwo conditions they revealQ values of 26395 and 25735MPafor as-cast M1S and T6-treated M4S respectively ose twoextreme conditions show that despite the considerable vari-ation in the UTS values on the one hand and ductility valueson the other for these two conditions the quality indices inboth cases remain almost unchanged due to the balancedtrade-off between the UTS and ductility values e relativelylowUTS and ductility values obtained at elevated temperature(250degC) for the T5-treated condition result in the T5-treatedalloys exhibiting minimum Q values among the conditionsstudied

Another interesting observation is that the quality indexvalues for alloys M2S and M3S in the T6-treated conditionare found to be the maximum for the alloys and conditionsstudied is observation highlights the enhanced charac-teristics of alloy M3S which contains 075wt Mn andemphasizes the positive influence of the high Mn-additionon the elevated-temperature tensile properties which arefound to be more or less comparable to those obtained withthe addition of 2 and 4wt Ni to the same base alloy

e favorable role of the blocky α-Al15(Fe Mn)3Si2phase termed as sludge particles in improving the tensileproperties of alloy M3S at 25degC and 250degC can be witnessed

from the fractograph of alloy M3S after testing at 250degCpresented in Figure 7 e sludge particles appear to retardthe propagation of the cracks developed in the other phaseswhich will subsequently enhance the mechanical propertiesof the respective alloy Yet another interesting observationmade from this figure is that while many of the intermetallicphase particles appear cracked as indicated by the solidarrows the sludge particles however are crack-freeWhereas the multiple cracked Ni-rich phases exist on thefracture surface of alloy M2S after testing at 250degC are be-lieved to contribute to the crack initiation process and hencedeteriorate the tensile properties of this alloy as witnessed inFigure 8

323 Hardness Values Figure 9 illustrates the variation inthe hardness values of the alloys as a function of the appliedheat treatment At first glance one can observe from Figure 9that the hardness values of different alloys show insignificantvariations for the same conditions For each alloy the peak-aged condition exhibits the highest hardness value among allconditions Also the tailored alloys ie M2S through M5Sshow better hardness values than those obtained for the basealloy in all the conditions studied

Variations in hardness values of the alloys in the as-castcondition can be attributed to the additions of Ni andor Mnmade to the base alloy M1S It was seen that additions of Niandor Mn in various amounts increased the volume frac-tions of intermetallic compounds considerably as listed inTable 3 e variations in hardness values follow the sametrend as variations in the percentage volume fraction ofintermetallic compounds us the base alloy M1S exhibitsthe lowest hardness value in the as-cast condition having thelowest volume fraction according to Table 3 and the highesthardness value of the same condition is associated with alloyM4S that has the highest volume fraction of intermetalliccompounds is observation highlights the effective role ofintermetallic compounds in enhancing the hardness values[19 50]

e dissolution of the strengthening elements over thecourse of the solution treatment reduces the hardness valuesin spite of the expected improved homogeneity in com-position and evolution of the eutectic silicon morphologyfollowing solution treatment is behavior emphasizes thecrucial role of intermetallic phases in influencing the me-chanical performance of alloys It is established that thehardness value of a specific alloy corresponds to the com-bination of the tensile yield strength and work-hardeningrate of the alloy [50 51] e order of the alloys studiedaccording to the hardness value in the as-quenched con-dition matches to a large extent their order with respect totheir yield strength in the same as-quenched condition(Figure 3)

Direct artificial aging following casting of test barsie T5-temper treatment introduces slight improvements inthe hardness values with respect to those obtained for the as-cast condition is can be attributed to the limited changesin the microstructure of the as-cast alloysbars followingdirect artificial aging without solution treatment e slight

Table 6 Variation in average UTS YS El and Q values of thealloys studied in as-cast and T5- and T6-treated conditions ob-tained at 250degC

Alloy Condition UTS(MPa)

YS(MPa) El Q (Equation (1))

M1SAs-cast 16995 15756 367 25465T5 17207 16151 202 21791T6 21765 21365 192 26014

M2SAs-cast 18632 17284 225 23915T5 19625 17885 160 22671T6 22372 22233 215 27365

M3SAs-cast 17576 16284 285 24399T5 18107 17745 161 21216T6 24874 24562 154 27668

M4SAs-cast 18053 16735 177 21757T5 18186 17913 132 19985T6 25358 25332 106 25735

M5SAs-cast 17648 16232 245 23492T5 19110 18402 176 22786T6 22209 22055 132 23996

12 Advances in Materials Science and Engineering

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

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contribute to variations in the free content of silicon andorstrontium Such variations may lead to a more efficientmodification in the case of a lower SiSr ratio and vice versa

On one hand a high amount of the copper in alloy M4S(containing 4 Ni) is consumed in forming Al3NiCu phase[11] and thus the possibility of forming the Al-Cu-Sr phasereported by Joenoes and Gruzleski [29] will be reducedConsequently more Sr will not be consumed to form the Al-Cu-Sr phase and thus better modification would be ex-pected for Ni-containing alloys particularly those withhigher Ni-content as in alloy M4S On the other hand theaddition of 075 wt Mn in alloy M3S changes some of theβ-Al5FeSi iron phase into Chinese script-like α-Al15(FeMn)3Si2 phase and sludge particles e mutual existence ofthe two Fe-based phases ie β-Al5FeSi and α-Al15(FeMn)3Si2 will lower the silicon content (ie reduce the Siphase) in alloy M3S to an extent which will allow a bettermodification level compared to that attained for the rest ofthe alloys studied as depicted in Figure 2(e)

ermal modification is yet another effective way toalter the morphology of eutectic silicon particles It isevident from the micrographs shown in Figure 2 on theright that the solution treatment changes the fibrousinterconnected eutectic silicon particles detected in the as-cast condition into globular particles with rounded edgese evolution of the morphology of the eutectic siliconparticles from fibrous to globular in these alloys is a directresult to the combined effect of solution-heat treatment andstrontium modification as previously stated by Chen et al[31] and Yuying et al [32]

It is evident from the data presented in Table 4 that theaverage Si particle area increases after solution treatment at495degC for 5 hours for all the alloys Additionally the sol-utionizing treatment produces a noticeable improvement inthe spheroidization of the Si particles concomitant withenhancements in the roundness values as can be seenqualitatively from the micrographs shown in Figure 2 eincrease in sphericity and roundness values would producea corresponding decrease in the aspect ratio as seen inTable 4

32 Mechanical Performance

321 Ambient-Temperature Tensile Testing In the presentstudy the sole addition of sim03 wt Zr to the 354-type Al-Si-Cu-Mg cast alloy (ie the base alloy M1S) in the as-castcondition enhances the ambient-temperature strengthvalues of the Zr-free 354 alloy (alloy A) used in previousinvestigations in the same group by Hernandez-Sandoval[16] by sim26MPa (UTS) and 40MPa (YS) respectivelyese enhancements in the strength values are accompaniedby a limited reduction in the alloy ductility (sim0054) Forthe solution heat-treated condition on the other hand theUTS and ductility values of the base alloy M1S remainvirtually constant at sim300MPa and sim63 respectivelywhile the yield strength increases by sim33MPa compared toalloy A in the work of Hernandez-Sandoval [16] e im-proved strength values of Zr-containing Al-Si-Cu-Mg alloy

emphasize the role of Zr addition in enhancing the ambient-temperature tensile properties

Figure 3 shows the ambient-temperature tensile prop-erties obtained for the alloys under investigation In the as-cast condition the base alloy M1S (354 + 03 wt Zr) showsthe lowest UTS and YS values As-cast strength values of theother alloys ie M2S through M5S show enhancements of14ndash25 and 16ndash26 in UTS and YS respectively comparedto the base alloy (M1S) However the ductility values ofalloys M2S through M5S show inconsistent variations withrespect to the ductility of the base alloy M1S these variationscomprise enhancements in case of alloy M3S deteriorationsin the case of alloys M4S and M5S and almost unchangedductility value in the case of alloy M2S

e probable explanations for the enhanced strengthvalues of alloy M3S are the formation of favorable phaseswhich are advantageous to the strength values and thehighly refined as-cast Si particles (Table 4) as a result to theaddition of 075 wt Mn to the base alloy (M1S) It is wellestablished that the addition of Mn neutralizes to someextent the deleterious effect of iron impurities by trans-forming the detrimental needle-like β-Al5FeSi phase into theless harmful α-Al15(Fe Mn)3Si2 phase which appears ineither script-like form or as blocky sludge particles or bothWhile there is no doubt about the positive effect of thescript-like α-phase on strength and ductility values there ismuch debate however on the effect of the sludge particleson the tensile properties either they are harmful as regularlybelieved [28 33 34] or favorable to the tensile properties[7 35 36] Garza-Elizondo [7] has reported that the presenceof these hard particles in the soft α-Al matrix may contributein enhancing the tensile properties through the developmentof more uniformly distributed stresses within the matrix

For the Ni-containing alloys enhancements in thestrength values can be correlated to the formation of Ni-containing intermetallic compounds such as Al9FeNiAl3CuNi and Al3Ni which can hinder the propagation ofcracks similar findings are reported in previous studies[11 16] Increasing the Ni content from 2wt to 4wtinversely affects the tensile properties at room temperatureIt is believed that the precipitation of higher volume frac-tions of the acicular Al9FeNi and Al3CuNi phases in the as-cast alloy M4S (4wt Ni) is responsible for the de-terioration of the tensile properties at room temperature

Apparently from Figure 3 the base alloy M1S proves tobe very responsive to solution heat treatment because itshows an increase of 40MPa and 8MPa in the as-cast UTSand YS values respectively after solutionizing at 495degC for 5hours In addition the ductility of the solutionizedM1S alloyalso shows an increase of sim5 over the ductility valueobtained for the as-cast condition On the other hand theother alloys ie M2S through M5S show small improve-ments in the range of 2ndash10MPa for UTS values anda noticeable reduction in YS values (18ndash36MPa) comparedto their strength values in the as-cast conditione ductilityvalues of alloys M2S through M5S increase after solutiontreatment e enhanced ductility values after solution heattreatment in particular are related to the changes in theeutectic silicon morphology Coarse acicular silicon particles

Advances in Materials Science and Engineering 7

serve as crack initiators which is the case in the as-castcondition whereas more spherical Si particles with roundededges and decreased aspect ratios are obtained in the so-lution heat-treated case

Figures 3(a) and 3(b) show that the strength values of thebase alloy M1S are 289MPa (UTS)259MPa (YS) and342MPa (UTS)325MPa (YS) in the T5- and T6-treatedconditions respectively Alloys M2S and M3S exhibit thehighest strength among the alloys studied with values of300MPa (UTS)277MPa (YS) and 315MPa (UTS)279MPa(YS) respectively in the T5-treated condition and 362MPa(UTS)352MPa (YS) and 357MPa (UTS)355MPa (YS) inthe T6-treated condition respectively e strength values(UTS and YS) of alloys M1S M2S (M1S+ 2wt Ni) andM3S (M1S+075wtMn) show distinct enhancements afterapplying the T6 treatment in comparison to the as-cast andas-solutionized conditions In contrast alloys M4S (M1S+4wt Ni) and M5S (M1S+2wt Ni+075wt Mn)exhibit a very limited enhancement in UTS (sim15MPa) after T6heat treatment with reference to their strength in the as-castand as-quenched conditions Additionally from Figure 3(c) itcan be seen that the ductility values reduce considerably afterT6 treatment when compared to the as-cast ductility values ofthe respective alloys Ductility values of the alloys studied arelimited in general due to the high silicon content sim9wt andthe presence of both Mg and Cu [30]

e enhanced strength values of alloy M2S particularlyfor the T6-treated condition can be attributed to thepresence of Ni-containing phases such as Al3Ni Al9FeNiand Al3CuNi in addition to the ne precipitates formedafter applying T6 treatment [37 38] With respect to alloyM3S the improved strength values following T5- and T6-heat treatments can be ascribed to (i) the presence ofα-Al15(Fe Mn)3Si2 in the form of blocky hard particles (ii)the precipitated strengthening Cu- and Mg-containingdispersoids and (iii) the probable formation of Al6Mnne dispersoids in the presence of a high Mn content of075 wt [39 40] e presence of these Mn dispersoidssignicantly improves the yield and ultimate strength valueswithout sacricing the ductility [39 41 42]

e presence of a high nickel content in T6-treated alloyM4S (4wt) results in deteriorating the ambient-temperature tensile properties as can be inferred fromFigure 3 similar observations have been noted by otherauthors [71043ndash46] is deterioration in the strengthvalues is a direct result of the high content of Ni which inturn will consume some of the available copper in the alloyto form the detected Al3CuNi phase As a result this willreduce the amount of copper available for strengtheningthrough precipitation hardening during heat treatment [10]Furthermore the precipitation of Al9FeNi and Al3CuNiphases in high volume fractions (Table 3) would facilitate

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(a)

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(b)

01234567

AC SHT T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

M1SM2SM3S

M4SM5S

(c)

Figure 3 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in as-cast solution heat-treated (SHT) and T5- andT6-treated conditions obtained at ambient temperature

8 Advances in Materials Science and Engineering

cracking since they would act as stress raisers causinginstability in the flow strain and hence the ductility of thisalloy will reduce accordingly

In general the room-temperature tensile properties inthe T6 heat-treated conditions are better than those obtainedwith the T5 treatment for the alloys studied e use ofpermanent mold casting which is the technique used forproducing the test bars would preserve copper and mag-nesium in considerable amounts in solid solution due to thehigh solidification rate us by applying artificial agingdirectly after solidification (ie T5 temper) large pro-portions of the dissolved Cu andMg in the solid solution willform strengthening dispersoids e T6 heat treatment onthe other hand involves solutionizing the as-cast structure ata sufficiently high temperature in order to dissolve higheramounts of Cu and Mg in solid solution in order to forma supersaturated solid solution upon quenching and toachieve further modification of the eutectic Si particlesus the artificial aging in the case of T6 treatment willprecipitate fine strengthening particles in larger proportionsthan in the case of T5 treatment which will enhance the alloystrength to a greater extent however at the expense ofductility

For the alloys studied the ambient-temperature tensiletesting data are listed in Table 5 along with the quality indexvalues which were calculated using Equations (1) and (2)according to the models developed by Drouzy et al [47] andCaceres [48] respectively

Q SUTS + dlog ef 1113857 (1)

Qc K (qn)n expminusqn + 04 log(100qn)1113858 1113859 (2)

where Q and Qc (MPa) are the quality indices according toDrouzy and Caceres models SUTS refers to the ultimatetensile strength (MPa) ef refers to the percentage elongationto fracture d is a material constant equal to 150MPaK is thestrength coefficient (MPa) relative quality index (q) and n isthe strain-hardening exponent

Figure 4 shows the quality chart for the alloys studiedbased on Drouzy [47] model and depicts variations in thequality index values based on the chemical composition andthe applied heat treatment Equations (1) and (3) were usedto develop the ldquoiso-Qrdquo and ldquoiso-YSrdquo lines in the chart

Sp(ys) aSUTS minus blog ef 1113857 + C (3)

where coefficients a b and c were quantified as 1 60MPaand minus13MPa respectively

e quality index values Q and Qc listed in Table 5 showthe same trend in variations however with different valuese difference between Q and Qc increases in the T5 and T6heat-treated conditions which can be accredited to the factthat the alloy quality is affected by the net amount by whichthe increase in strength is balanced by the reduction inductility As can be seen from Table 5 and Figure 4 the bestquality values for the alloys are obtained after solution heattreatment attributed to the microstructural changes thattake place during the solution treatment including thedissolution of strengthening elements the homogenization

of the segregated as-cast structure and the spheroidizationof the eutectic silicon particles ese changes will signifi-cantly enhance the alloy ductility in addition to a limitedenhancement in UTS values Consequently the quality in-dex values of the as-quenched (or solution heat-treated)alloys are remarkably higher than those in the as-castcondition

While the T6 heat treatment improves the UTS valuesconsiderably in comparison to the UTS values obtainedafter solution treatment it does so at the expense of theductility is trade-off between UTS and ductility valueswill certainly affect the quality index values and not nec-essarily in a positive way Likewise a similar behavior isnoted for the T5-treated alloys as well as can be inferredfrom Figure 4

It is evident that the superior ductility of the base alloyM1S is the main reason for the improved quality indices ofthis alloy in the majority of the conditions studied On theother hand the mutual enhancement in the strength andductility values of alloys M2S and M3S compared to those ofalloys M4S and M5S is responsible for the higher qualityindices of the former compared to those of the latter

e addition of Mn in alloy M3S results in transformingthe needles of the β-iron phase into the less detrimentalα-iron phase this favorable morphological change is be-lieved to improve the ductility and strength values of alloyM3S Whereas the structure of alloy M2S contains Ni-bearing phases with acicular morphologies and β-ironneedles that negatively affect the mechanical propertiesAccordingly the quality index values of alloy M3S are higherthan those of the 2wt Ni-containing alloy M2S in the as-cast SHT and T5 conditions In contrast the quality indexvalues of the T6-treated alloysM2S andM3S show a reversedbehavior according to the marginal variations in their tensileproperties and hence the quality index values

From Table 5 it is observable that the quality indexvalues calculated using Drouzyrsquos approach are higher thanthose obtained by the model developed by Caceres for alltreatment conditions per each alloy except for solution-treated conditions is can be attributed to the improvedductility of as-quenched conditions that will allow moreaccurate determination of the material parameters (K andn) us it would be advisable to calculate the quality indexvalues of solution-treated conditions using Caceresrsquo modelespecially for materials with low ductility at roomtemperature

322 Elevated-Temperature Tensile Testing Figure 5 revealsthe elevated-temperature tensile properties obtained at250degC for the alloys studied By tensile testing at 250degC allthe investigated alloys endure some softening owing to thepossible coarsening of the strengthening precipitates thatexist during tensile testing at room temperature (Figure 3)Figures 5(a) and 5(b) demonstrate that additions of Ni andMn in different amounts and combinations to the base alloyie alloys M2S through M5S slightly improve the strengthvalues of the base alloy in the range of 5ndash15MPa for both as-cast and T5-treated conditions e tight enhancement in

Advances in Materials Science and Engineering 9

strength values of the T5-treated conditions can be ascribed tothe limited variations in themicrostructural features of as-caststructures as well as to the low proportion of strengtheningprecipitates in the structure of T5-treated alloys

In regard to the ductility values in the as-cast conditionFigure 5(c) reveals that the highest ductility value is observedto be associated with the base alloy M1S with a value of

sim36 followed by the ductility of the Mn-containing alloysM3S andM5S and ending up with the lowest ductility valuesfor alloys M2S and M4S containing 2 and 4wt Ni re-spectively e higher ductility values of the as-cast Mn-containing alloys M3S andM5S can be attributed to the well-refined Si particles Table 4 and the transformation ofa considerable amount of β-Al5FeSi needles which may act

Table 5 Variation in average UTS YS El Qc and Q values of the alloys studied in as-cast SHT and T5- and T6-treated conditionsobtained at ambient temperature

Alloy Condition UTS(MPa)

YS(MPa)

Totalstrain ()

Plasticstrain () E (GPa) n K q Qc

(Equation (2))Q

(Equation (1))Difference

(QminusQc) (MPa)

M1S

As-cast 26086 19439 158 116 6266 018 58056 007 27788 29050 1262SHT 30034 20251 622 574 6250 017 57926 034 51236 41943 minus9293T5 28950 25875 094 048 6306 013 59169 004 21706 28543 6838T6 34195 32499 11075 056 6245 010 57691 006 28153 34860 6707

M2S

As-cast 32035 23585 163 116 6758 019 76378 006 34214 35219 1005SHT 32774 21261 320 270 6623 017 75932 016 53109 40343 minus12766T5 29997 27719 080 034 6564 015 70196 002 16710 28522 11812T6 36233 35157 080 024 6471 011 70779 002 19604 34816 15212

M3S

As-cast 32578 24572 176 126 6473 015 64889 008 35471 36255 784SHT 33475 20943 381 330 6447 012 64647 027 54926 42197 minus12729T5 31458 27939 098 049 6414 013 63449 004 23821 31310 7489T6 35701 35514 075 020 6432 008 62421 002 19202 33850 14648

M4S

As-cast 30440 22461 133 087 6610 020 83677 004 29364 32287 2923SHT 31232 20709 222 175 6656 018 82135 010 46959 36427 minus10532T5 27644 25414 071 031 6843 020 85707 002 9928 25451 15524T6 31598 31598 05705 011 6710 010 63474 001 7752 27941 20189

M5S

As-cast 29707 22659 127 083 6691 020 79201 004 27391 31280 3889SHT 29979 20664 199 154 6735 017 78035 009 43714 34462 minus9252T5 28461 27700 066 022 6474 015 72211 001 9720 25745 16025T6 31404 31404 056 011 6789 011 67764 001 4543 27632 23089

1

23

12

3

1 2

3

12

3

1 23

250

300

350

400

05 5

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

Drouzy quality index chart room temperature

M1SM2SM3S

M4SM5S

4 4

44

YS = 350 MPa

Q = 500 MPaQ = 450 MPa

Q = 350 MPa

Q = 250 MPa

Q = 300 MPa

Q = 400 MPa

YS = 250 MPa

4

1 as-cast2 SHT3 T54 T6

Figure 4 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast SHT and T5- and T6-treated conditions obtained at ambient temperature

10 Advances in Materials Science and Engineering

as crack initiators into the less detrimental α-Al15(MnFe)3Si2 phase with script-like andor sludge morphologies

e addition of Ni on the other hand lowers theductility values even for alloy M5S that contains 075wtMn when compared to alloy M3S which is Ni-free ereduction in ductility values of the as-cast Ni-containingalloys can be directly correlated to the presence of acicularNi-bearing phases with sharp edges such as Al3Ni Al9FeNiand Al3CuNi phases Variation in chemical compositionshas a limited eiexclect on the ductility values obtained at 250degCfor the T5-treated alloys since the maximum absolutediiexclerence in the ductility values of alloys M2S through M5Sis found to be sim044 Application of T5 and T6 heattreatments reduces the ductility observed in the as-castcondition e ductility values in the T6-treated conditionare generally lower than those obtained with T5 treatmentconditions

e application of the T6 heat treatment enhances thestrength values of as-cast conditions regardless the alloycomposition as shown in Figures 5(a) and 5(b) e en-hanced strength values of alloy M4S after T6 heat treatmentmay be attributed to the presence of δ-Al3CuNi and eutecticAl-Al3Ni phases that prove to contribute eiexclectively to theelevated-temperature strength of alloy M4S in spite ofa considerable amount of Cu that is consumed in formingthe δ-Al3CuNi phase which will certainly aiexclect the amount

of ne Al2Cu dispersoids formed which is consistent withthe ndings reported in references [38 49]

Interestingly alloys M3S (354 + 075wt Mn) and M4S(354 + 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the diiexclerent conditions ex-amined Moreover alloy M3S is considered to be morefavorable between the two since it exhibits higher ductilitythan that of the Ni-containing alloy M4S ese two alloysexhibit the best strength values (UTS and YS) in the T6-treated conditions among the investigated alloys whereasthe strength values of the other three alloys ie alloys M1SM2S and M5S are close to each other and lower than thestrength values obtained for alloys M3S and M4S bysim36MPa is observation would emphasize the advanta-geous role of adding Mn instead of Ni to enhance theelevated-temperature tensile properties along with its eco-nomic impact

Generally the closeness of the elevated-temperaturestrength values of the alloys studied can be credited tothe presence of 03 wt Zr in each alloy whereby theformation of the ne metastable L12-Al3Zr particles is ex-pected in the microstructures of all the alloys which in turnwill improve the alloy strength in a common manner

For elevated-temperature tensile properties the conceptof the quality index will be discussed according to theconcept of Drouzy et al [47] (Q) Table 6 demonstrates the

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditionsM1SM2SM3S

M4SM5S

(a)

M1SM2SM3S

M4SM5S

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditions

(b)

M1SM2SM3S

M4SM5S

005

115

225

335

445

AC T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

(c)

Figure 5 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in the as-cast solution heat-treated (SHT) and T5-and T6-treated conditions obtained at 250degC

Advances in Materials Science and Engineering 11

elevated-temperature tensile data along with the quality indexvalues (Q) of the alloys studied calculated using Equation (1)Figure 6 shows the quality chart obtained based on the cal-culations of Drouzy et al [47] As may be seen the qualityindex values obtained at 250degC do not show wide variation invalues as was observed in the case of the ambient-temperature data is limited variation can be understoodin light of the balanced variation in UTS and ductility valuesobtained at the elevated temperature of 250degC For examplethe base alloyM1S in the as-cast condition exhibits the highestductility value of 367 and a UTS value of 16995MPa whilethe lowest ductility is experienced by alloy M4S for the T6-treated condition with a value of 106 along with a UTSvalue of 25358MPa By calculating the quality indices of thesetwo conditions they revealQ values of 26395 and 25735MPafor as-cast M1S and T6-treated M4S respectively ose twoextreme conditions show that despite the considerable vari-ation in the UTS values on the one hand and ductility valueson the other for these two conditions the quality indices inboth cases remain almost unchanged due to the balancedtrade-off between the UTS and ductility values e relativelylowUTS and ductility values obtained at elevated temperature(250degC) for the T5-treated condition result in the T5-treatedalloys exhibiting minimum Q values among the conditionsstudied

Another interesting observation is that the quality indexvalues for alloys M2S and M3S in the T6-treated conditionare found to be the maximum for the alloys and conditionsstudied is observation highlights the enhanced charac-teristics of alloy M3S which contains 075wt Mn andemphasizes the positive influence of the high Mn-additionon the elevated-temperature tensile properties which arefound to be more or less comparable to those obtained withthe addition of 2 and 4wt Ni to the same base alloy

e favorable role of the blocky α-Al15(Fe Mn)3Si2phase termed as sludge particles in improving the tensileproperties of alloy M3S at 25degC and 250degC can be witnessed

from the fractograph of alloy M3S after testing at 250degCpresented in Figure 7 e sludge particles appear to retardthe propagation of the cracks developed in the other phaseswhich will subsequently enhance the mechanical propertiesof the respective alloy Yet another interesting observationmade from this figure is that while many of the intermetallicphase particles appear cracked as indicated by the solidarrows the sludge particles however are crack-freeWhereas the multiple cracked Ni-rich phases exist on thefracture surface of alloy M2S after testing at 250degC are be-lieved to contribute to the crack initiation process and hencedeteriorate the tensile properties of this alloy as witnessed inFigure 8

323 Hardness Values Figure 9 illustrates the variation inthe hardness values of the alloys as a function of the appliedheat treatment At first glance one can observe from Figure 9that the hardness values of different alloys show insignificantvariations for the same conditions For each alloy the peak-aged condition exhibits the highest hardness value among allconditions Also the tailored alloys ie M2S through M5Sshow better hardness values than those obtained for the basealloy in all the conditions studied

Variations in hardness values of the alloys in the as-castcondition can be attributed to the additions of Ni andor Mnmade to the base alloy M1S It was seen that additions of Niandor Mn in various amounts increased the volume frac-tions of intermetallic compounds considerably as listed inTable 3 e variations in hardness values follow the sametrend as variations in the percentage volume fraction ofintermetallic compounds us the base alloy M1S exhibitsthe lowest hardness value in the as-cast condition having thelowest volume fraction according to Table 3 and the highesthardness value of the same condition is associated with alloyM4S that has the highest volume fraction of intermetalliccompounds is observation highlights the effective role ofintermetallic compounds in enhancing the hardness values[19 50]

e dissolution of the strengthening elements over thecourse of the solution treatment reduces the hardness valuesin spite of the expected improved homogeneity in com-position and evolution of the eutectic silicon morphologyfollowing solution treatment is behavior emphasizes thecrucial role of intermetallic phases in influencing the me-chanical performance of alloys It is established that thehardness value of a specific alloy corresponds to the com-bination of the tensile yield strength and work-hardeningrate of the alloy [50 51] e order of the alloys studiedaccording to the hardness value in the as-quenched con-dition matches to a large extent their order with respect totheir yield strength in the same as-quenched condition(Figure 3)

Direct artificial aging following casting of test barsie T5-temper treatment introduces slight improvements inthe hardness values with respect to those obtained for the as-cast condition is can be attributed to the limited changesin the microstructure of the as-cast alloysbars followingdirect artificial aging without solution treatment e slight

Table 6 Variation in average UTS YS El and Q values of thealloys studied in as-cast and T5- and T6-treated conditions ob-tained at 250degC

Alloy Condition UTS(MPa)

YS(MPa) El Q (Equation (1))

M1SAs-cast 16995 15756 367 25465T5 17207 16151 202 21791T6 21765 21365 192 26014

M2SAs-cast 18632 17284 225 23915T5 19625 17885 160 22671T6 22372 22233 215 27365

M3SAs-cast 17576 16284 285 24399T5 18107 17745 161 21216T6 24874 24562 154 27668

M4SAs-cast 18053 16735 177 21757T5 18186 17913 132 19985T6 25358 25332 106 25735

M5SAs-cast 17648 16232 245 23492T5 19110 18402 176 22786T6 22209 22055 132 23996

12 Advances in Materials Science and Engineering

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

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Submit your manuscripts atwwwhindawicom

serve as crack initiators which is the case in the as-castcondition whereas more spherical Si particles with roundededges and decreased aspect ratios are obtained in the so-lution heat-treated case

Figures 3(a) and 3(b) show that the strength values of thebase alloy M1S are 289MPa (UTS)259MPa (YS) and342MPa (UTS)325MPa (YS) in the T5- and T6-treatedconditions respectively Alloys M2S and M3S exhibit thehighest strength among the alloys studied with values of300MPa (UTS)277MPa (YS) and 315MPa (UTS)279MPa(YS) respectively in the T5-treated condition and 362MPa(UTS)352MPa (YS) and 357MPa (UTS)355MPa (YS) inthe T6-treated condition respectively e strength values(UTS and YS) of alloys M1S M2S (M1S+ 2wt Ni) andM3S (M1S+075wtMn) show distinct enhancements afterapplying the T6 treatment in comparison to the as-cast andas-solutionized conditions In contrast alloys M4S (M1S+4wt Ni) and M5S (M1S+2wt Ni+075wt Mn)exhibit a very limited enhancement in UTS (sim15MPa) after T6heat treatment with reference to their strength in the as-castand as-quenched conditions Additionally from Figure 3(c) itcan be seen that the ductility values reduce considerably afterT6 treatment when compared to the as-cast ductility values ofthe respective alloys Ductility values of the alloys studied arelimited in general due to the high silicon content sim9wt andthe presence of both Mg and Cu [30]

e enhanced strength values of alloy M2S particularlyfor the T6-treated condition can be attributed to thepresence of Ni-containing phases such as Al3Ni Al9FeNiand Al3CuNi in addition to the ne precipitates formedafter applying T6 treatment [37 38] With respect to alloyM3S the improved strength values following T5- and T6-heat treatments can be ascribed to (i) the presence ofα-Al15(Fe Mn)3Si2 in the form of blocky hard particles (ii)the precipitated strengthening Cu- and Mg-containingdispersoids and (iii) the probable formation of Al6Mnne dispersoids in the presence of a high Mn content of075 wt [39 40] e presence of these Mn dispersoidssignicantly improves the yield and ultimate strength valueswithout sacricing the ductility [39 41 42]

e presence of a high nickel content in T6-treated alloyM4S (4wt) results in deteriorating the ambient-temperature tensile properties as can be inferred fromFigure 3 similar observations have been noted by otherauthors [71043ndash46] is deterioration in the strengthvalues is a direct result of the high content of Ni which inturn will consume some of the available copper in the alloyto form the detected Al3CuNi phase As a result this willreduce the amount of copper available for strengtheningthrough precipitation hardening during heat treatment [10]Furthermore the precipitation of Al9FeNi and Al3CuNiphases in high volume fractions (Table 3) would facilitate

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(a)

150

200

250

300

350

400

AC SHT T5 T6

Stre

ngth

(MPa

)

Treatment conditions

M1SM2SM3S

M4SM5S

(b)

01234567

AC SHT T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

M1SM2SM3S

M4SM5S

(c)

Figure 3 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in as-cast solution heat-treated (SHT) and T5- andT6-treated conditions obtained at ambient temperature

8 Advances in Materials Science and Engineering

cracking since they would act as stress raisers causinginstability in the flow strain and hence the ductility of thisalloy will reduce accordingly

In general the room-temperature tensile properties inthe T6 heat-treated conditions are better than those obtainedwith the T5 treatment for the alloys studied e use ofpermanent mold casting which is the technique used forproducing the test bars would preserve copper and mag-nesium in considerable amounts in solid solution due to thehigh solidification rate us by applying artificial agingdirectly after solidification (ie T5 temper) large pro-portions of the dissolved Cu andMg in the solid solution willform strengthening dispersoids e T6 heat treatment onthe other hand involves solutionizing the as-cast structure ata sufficiently high temperature in order to dissolve higheramounts of Cu and Mg in solid solution in order to forma supersaturated solid solution upon quenching and toachieve further modification of the eutectic Si particlesus the artificial aging in the case of T6 treatment willprecipitate fine strengthening particles in larger proportionsthan in the case of T5 treatment which will enhance the alloystrength to a greater extent however at the expense ofductility

For the alloys studied the ambient-temperature tensiletesting data are listed in Table 5 along with the quality indexvalues which were calculated using Equations (1) and (2)according to the models developed by Drouzy et al [47] andCaceres [48] respectively

Q SUTS + dlog ef 1113857 (1)

Qc K (qn)n expminusqn + 04 log(100qn)1113858 1113859 (2)

where Q and Qc (MPa) are the quality indices according toDrouzy and Caceres models SUTS refers to the ultimatetensile strength (MPa) ef refers to the percentage elongationto fracture d is a material constant equal to 150MPaK is thestrength coefficient (MPa) relative quality index (q) and n isthe strain-hardening exponent

Figure 4 shows the quality chart for the alloys studiedbased on Drouzy [47] model and depicts variations in thequality index values based on the chemical composition andthe applied heat treatment Equations (1) and (3) were usedto develop the ldquoiso-Qrdquo and ldquoiso-YSrdquo lines in the chart

Sp(ys) aSUTS minus blog ef 1113857 + C (3)

where coefficients a b and c were quantified as 1 60MPaand minus13MPa respectively

e quality index values Q and Qc listed in Table 5 showthe same trend in variations however with different valuese difference between Q and Qc increases in the T5 and T6heat-treated conditions which can be accredited to the factthat the alloy quality is affected by the net amount by whichthe increase in strength is balanced by the reduction inductility As can be seen from Table 5 and Figure 4 the bestquality values for the alloys are obtained after solution heattreatment attributed to the microstructural changes thattake place during the solution treatment including thedissolution of strengthening elements the homogenization

of the segregated as-cast structure and the spheroidizationof the eutectic silicon particles ese changes will signifi-cantly enhance the alloy ductility in addition to a limitedenhancement in UTS values Consequently the quality in-dex values of the as-quenched (or solution heat-treated)alloys are remarkably higher than those in the as-castcondition

While the T6 heat treatment improves the UTS valuesconsiderably in comparison to the UTS values obtainedafter solution treatment it does so at the expense of theductility is trade-off between UTS and ductility valueswill certainly affect the quality index values and not nec-essarily in a positive way Likewise a similar behavior isnoted for the T5-treated alloys as well as can be inferredfrom Figure 4

It is evident that the superior ductility of the base alloyM1S is the main reason for the improved quality indices ofthis alloy in the majority of the conditions studied On theother hand the mutual enhancement in the strength andductility values of alloys M2S and M3S compared to those ofalloys M4S and M5S is responsible for the higher qualityindices of the former compared to those of the latter

e addition of Mn in alloy M3S results in transformingthe needles of the β-iron phase into the less detrimentalα-iron phase this favorable morphological change is be-lieved to improve the ductility and strength values of alloyM3S Whereas the structure of alloy M2S contains Ni-bearing phases with acicular morphologies and β-ironneedles that negatively affect the mechanical propertiesAccordingly the quality index values of alloy M3S are higherthan those of the 2wt Ni-containing alloy M2S in the as-cast SHT and T5 conditions In contrast the quality indexvalues of the T6-treated alloysM2S andM3S show a reversedbehavior according to the marginal variations in their tensileproperties and hence the quality index values

From Table 5 it is observable that the quality indexvalues calculated using Drouzyrsquos approach are higher thanthose obtained by the model developed by Caceres for alltreatment conditions per each alloy except for solution-treated conditions is can be attributed to the improvedductility of as-quenched conditions that will allow moreaccurate determination of the material parameters (K andn) us it would be advisable to calculate the quality indexvalues of solution-treated conditions using Caceresrsquo modelespecially for materials with low ductility at roomtemperature

322 Elevated-Temperature Tensile Testing Figure 5 revealsthe elevated-temperature tensile properties obtained at250degC for the alloys studied By tensile testing at 250degC allthe investigated alloys endure some softening owing to thepossible coarsening of the strengthening precipitates thatexist during tensile testing at room temperature (Figure 3)Figures 5(a) and 5(b) demonstrate that additions of Ni andMn in different amounts and combinations to the base alloyie alloys M2S through M5S slightly improve the strengthvalues of the base alloy in the range of 5ndash15MPa for both as-cast and T5-treated conditions e tight enhancement in

Advances in Materials Science and Engineering 9

strength values of the T5-treated conditions can be ascribed tothe limited variations in themicrostructural features of as-caststructures as well as to the low proportion of strengtheningprecipitates in the structure of T5-treated alloys

In regard to the ductility values in the as-cast conditionFigure 5(c) reveals that the highest ductility value is observedto be associated with the base alloy M1S with a value of

sim36 followed by the ductility of the Mn-containing alloysM3S andM5S and ending up with the lowest ductility valuesfor alloys M2S and M4S containing 2 and 4wt Ni re-spectively e higher ductility values of the as-cast Mn-containing alloys M3S andM5S can be attributed to the well-refined Si particles Table 4 and the transformation ofa considerable amount of β-Al5FeSi needles which may act

Table 5 Variation in average UTS YS El Qc and Q values of the alloys studied in as-cast SHT and T5- and T6-treated conditionsobtained at ambient temperature

Alloy Condition UTS(MPa)

YS(MPa)

Totalstrain ()

Plasticstrain () E (GPa) n K q Qc

(Equation (2))Q

(Equation (1))Difference

(QminusQc) (MPa)

M1S

As-cast 26086 19439 158 116 6266 018 58056 007 27788 29050 1262SHT 30034 20251 622 574 6250 017 57926 034 51236 41943 minus9293T5 28950 25875 094 048 6306 013 59169 004 21706 28543 6838T6 34195 32499 11075 056 6245 010 57691 006 28153 34860 6707

M2S

As-cast 32035 23585 163 116 6758 019 76378 006 34214 35219 1005SHT 32774 21261 320 270 6623 017 75932 016 53109 40343 minus12766T5 29997 27719 080 034 6564 015 70196 002 16710 28522 11812T6 36233 35157 080 024 6471 011 70779 002 19604 34816 15212

M3S

As-cast 32578 24572 176 126 6473 015 64889 008 35471 36255 784SHT 33475 20943 381 330 6447 012 64647 027 54926 42197 minus12729T5 31458 27939 098 049 6414 013 63449 004 23821 31310 7489T6 35701 35514 075 020 6432 008 62421 002 19202 33850 14648

M4S

As-cast 30440 22461 133 087 6610 020 83677 004 29364 32287 2923SHT 31232 20709 222 175 6656 018 82135 010 46959 36427 minus10532T5 27644 25414 071 031 6843 020 85707 002 9928 25451 15524T6 31598 31598 05705 011 6710 010 63474 001 7752 27941 20189

M5S

As-cast 29707 22659 127 083 6691 020 79201 004 27391 31280 3889SHT 29979 20664 199 154 6735 017 78035 009 43714 34462 minus9252T5 28461 27700 066 022 6474 015 72211 001 9720 25745 16025T6 31404 31404 056 011 6789 011 67764 001 4543 27632 23089

1

23

12

3

1 2

3

12

3

1 23

250

300

350

400

05 5

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

Drouzy quality index chart room temperature

M1SM2SM3S

M4SM5S

4 4

44

YS = 350 MPa

Q = 500 MPaQ = 450 MPa

Q = 350 MPa

Q = 250 MPa

Q = 300 MPa

Q = 400 MPa

YS = 250 MPa

4

1 as-cast2 SHT3 T54 T6

Figure 4 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast SHT and T5- and T6-treated conditions obtained at ambient temperature

10 Advances in Materials Science and Engineering

as crack initiators into the less detrimental α-Al15(MnFe)3Si2 phase with script-like andor sludge morphologies

e addition of Ni on the other hand lowers theductility values even for alloy M5S that contains 075wtMn when compared to alloy M3S which is Ni-free ereduction in ductility values of the as-cast Ni-containingalloys can be directly correlated to the presence of acicularNi-bearing phases with sharp edges such as Al3Ni Al9FeNiand Al3CuNi phases Variation in chemical compositionshas a limited eiexclect on the ductility values obtained at 250degCfor the T5-treated alloys since the maximum absolutediiexclerence in the ductility values of alloys M2S through M5Sis found to be sim044 Application of T5 and T6 heattreatments reduces the ductility observed in the as-castcondition e ductility values in the T6-treated conditionare generally lower than those obtained with T5 treatmentconditions

e application of the T6 heat treatment enhances thestrength values of as-cast conditions regardless the alloycomposition as shown in Figures 5(a) and 5(b) e en-hanced strength values of alloy M4S after T6 heat treatmentmay be attributed to the presence of δ-Al3CuNi and eutecticAl-Al3Ni phases that prove to contribute eiexclectively to theelevated-temperature strength of alloy M4S in spite ofa considerable amount of Cu that is consumed in formingthe δ-Al3CuNi phase which will certainly aiexclect the amount

of ne Al2Cu dispersoids formed which is consistent withthe ndings reported in references [38 49]

Interestingly alloys M3S (354 + 075wt Mn) and M4S(354 + 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the diiexclerent conditions ex-amined Moreover alloy M3S is considered to be morefavorable between the two since it exhibits higher ductilitythan that of the Ni-containing alloy M4S ese two alloysexhibit the best strength values (UTS and YS) in the T6-treated conditions among the investigated alloys whereasthe strength values of the other three alloys ie alloys M1SM2S and M5S are close to each other and lower than thestrength values obtained for alloys M3S and M4S bysim36MPa is observation would emphasize the advanta-geous role of adding Mn instead of Ni to enhance theelevated-temperature tensile properties along with its eco-nomic impact

Generally the closeness of the elevated-temperaturestrength values of the alloys studied can be credited tothe presence of 03 wt Zr in each alloy whereby theformation of the ne metastable L12-Al3Zr particles is ex-pected in the microstructures of all the alloys which in turnwill improve the alloy strength in a common manner

For elevated-temperature tensile properties the conceptof the quality index will be discussed according to theconcept of Drouzy et al [47] (Q) Table 6 demonstrates the

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditionsM1SM2SM3S

M4SM5S

(a)

M1SM2SM3S

M4SM5S

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditions

(b)

M1SM2SM3S

M4SM5S

005

115

225

335

445

AC T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

(c)

Figure 5 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in the as-cast solution heat-treated (SHT) and T5-and T6-treated conditions obtained at 250degC

Advances in Materials Science and Engineering 11

elevated-temperature tensile data along with the quality indexvalues (Q) of the alloys studied calculated using Equation (1)Figure 6 shows the quality chart obtained based on the cal-culations of Drouzy et al [47] As may be seen the qualityindex values obtained at 250degC do not show wide variation invalues as was observed in the case of the ambient-temperature data is limited variation can be understoodin light of the balanced variation in UTS and ductility valuesobtained at the elevated temperature of 250degC For examplethe base alloyM1S in the as-cast condition exhibits the highestductility value of 367 and a UTS value of 16995MPa whilethe lowest ductility is experienced by alloy M4S for the T6-treated condition with a value of 106 along with a UTSvalue of 25358MPa By calculating the quality indices of thesetwo conditions they revealQ values of 26395 and 25735MPafor as-cast M1S and T6-treated M4S respectively ose twoextreme conditions show that despite the considerable vari-ation in the UTS values on the one hand and ductility valueson the other for these two conditions the quality indices inboth cases remain almost unchanged due to the balancedtrade-off between the UTS and ductility values e relativelylowUTS and ductility values obtained at elevated temperature(250degC) for the T5-treated condition result in the T5-treatedalloys exhibiting minimum Q values among the conditionsstudied

Another interesting observation is that the quality indexvalues for alloys M2S and M3S in the T6-treated conditionare found to be the maximum for the alloys and conditionsstudied is observation highlights the enhanced charac-teristics of alloy M3S which contains 075wt Mn andemphasizes the positive influence of the high Mn-additionon the elevated-temperature tensile properties which arefound to be more or less comparable to those obtained withthe addition of 2 and 4wt Ni to the same base alloy

e favorable role of the blocky α-Al15(Fe Mn)3Si2phase termed as sludge particles in improving the tensileproperties of alloy M3S at 25degC and 250degC can be witnessed

from the fractograph of alloy M3S after testing at 250degCpresented in Figure 7 e sludge particles appear to retardthe propagation of the cracks developed in the other phaseswhich will subsequently enhance the mechanical propertiesof the respective alloy Yet another interesting observationmade from this figure is that while many of the intermetallicphase particles appear cracked as indicated by the solidarrows the sludge particles however are crack-freeWhereas the multiple cracked Ni-rich phases exist on thefracture surface of alloy M2S after testing at 250degC are be-lieved to contribute to the crack initiation process and hencedeteriorate the tensile properties of this alloy as witnessed inFigure 8

323 Hardness Values Figure 9 illustrates the variation inthe hardness values of the alloys as a function of the appliedheat treatment At first glance one can observe from Figure 9that the hardness values of different alloys show insignificantvariations for the same conditions For each alloy the peak-aged condition exhibits the highest hardness value among allconditions Also the tailored alloys ie M2S through M5Sshow better hardness values than those obtained for the basealloy in all the conditions studied

Variations in hardness values of the alloys in the as-castcondition can be attributed to the additions of Ni andor Mnmade to the base alloy M1S It was seen that additions of Niandor Mn in various amounts increased the volume frac-tions of intermetallic compounds considerably as listed inTable 3 e variations in hardness values follow the sametrend as variations in the percentage volume fraction ofintermetallic compounds us the base alloy M1S exhibitsthe lowest hardness value in the as-cast condition having thelowest volume fraction according to Table 3 and the highesthardness value of the same condition is associated with alloyM4S that has the highest volume fraction of intermetalliccompounds is observation highlights the effective role ofintermetallic compounds in enhancing the hardness values[19 50]

e dissolution of the strengthening elements over thecourse of the solution treatment reduces the hardness valuesin spite of the expected improved homogeneity in com-position and evolution of the eutectic silicon morphologyfollowing solution treatment is behavior emphasizes thecrucial role of intermetallic phases in influencing the me-chanical performance of alloys It is established that thehardness value of a specific alloy corresponds to the com-bination of the tensile yield strength and work-hardeningrate of the alloy [50 51] e order of the alloys studiedaccording to the hardness value in the as-quenched con-dition matches to a large extent their order with respect totheir yield strength in the same as-quenched condition(Figure 3)

Direct artificial aging following casting of test barsie T5-temper treatment introduces slight improvements inthe hardness values with respect to those obtained for the as-cast condition is can be attributed to the limited changesin the microstructure of the as-cast alloysbars followingdirect artificial aging without solution treatment e slight

Table 6 Variation in average UTS YS El and Q values of thealloys studied in as-cast and T5- and T6-treated conditions ob-tained at 250degC

Alloy Condition UTS(MPa)

YS(MPa) El Q (Equation (1))

M1SAs-cast 16995 15756 367 25465T5 17207 16151 202 21791T6 21765 21365 192 26014

M2SAs-cast 18632 17284 225 23915T5 19625 17885 160 22671T6 22372 22233 215 27365

M3SAs-cast 17576 16284 285 24399T5 18107 17745 161 21216T6 24874 24562 154 27668

M4SAs-cast 18053 16735 177 21757T5 18186 17913 132 19985T6 25358 25332 106 25735

M5SAs-cast 17648 16232 245 23492T5 19110 18402 176 22786T6 22209 22055 132 23996

12 Advances in Materials Science and Engineering

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

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Analytical ChemistryInternational Journal of

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Advances in Condensed Matter Physics

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Applied ChemistryJournal of

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Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

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Hindawiwwwhindawicom Volume 2018

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cracking since they would act as stress raisers causinginstability in the flow strain and hence the ductility of thisalloy will reduce accordingly

In general the room-temperature tensile properties inthe T6 heat-treated conditions are better than those obtainedwith the T5 treatment for the alloys studied e use ofpermanent mold casting which is the technique used forproducing the test bars would preserve copper and mag-nesium in considerable amounts in solid solution due to thehigh solidification rate us by applying artificial agingdirectly after solidification (ie T5 temper) large pro-portions of the dissolved Cu andMg in the solid solution willform strengthening dispersoids e T6 heat treatment onthe other hand involves solutionizing the as-cast structure ata sufficiently high temperature in order to dissolve higheramounts of Cu and Mg in solid solution in order to forma supersaturated solid solution upon quenching and toachieve further modification of the eutectic Si particlesus the artificial aging in the case of T6 treatment willprecipitate fine strengthening particles in larger proportionsthan in the case of T5 treatment which will enhance the alloystrength to a greater extent however at the expense ofductility

For the alloys studied the ambient-temperature tensiletesting data are listed in Table 5 along with the quality indexvalues which were calculated using Equations (1) and (2)according to the models developed by Drouzy et al [47] andCaceres [48] respectively

Q SUTS + dlog ef 1113857 (1)

Qc K (qn)n expminusqn + 04 log(100qn)1113858 1113859 (2)

where Q and Qc (MPa) are the quality indices according toDrouzy and Caceres models SUTS refers to the ultimatetensile strength (MPa) ef refers to the percentage elongationto fracture d is a material constant equal to 150MPaK is thestrength coefficient (MPa) relative quality index (q) and n isthe strain-hardening exponent

Figure 4 shows the quality chart for the alloys studiedbased on Drouzy [47] model and depicts variations in thequality index values based on the chemical composition andthe applied heat treatment Equations (1) and (3) were usedto develop the ldquoiso-Qrdquo and ldquoiso-YSrdquo lines in the chart

Sp(ys) aSUTS minus blog ef 1113857 + C (3)

where coefficients a b and c were quantified as 1 60MPaand minus13MPa respectively

e quality index values Q and Qc listed in Table 5 showthe same trend in variations however with different valuese difference between Q and Qc increases in the T5 and T6heat-treated conditions which can be accredited to the factthat the alloy quality is affected by the net amount by whichthe increase in strength is balanced by the reduction inductility As can be seen from Table 5 and Figure 4 the bestquality values for the alloys are obtained after solution heattreatment attributed to the microstructural changes thattake place during the solution treatment including thedissolution of strengthening elements the homogenization

of the segregated as-cast structure and the spheroidizationof the eutectic silicon particles ese changes will signifi-cantly enhance the alloy ductility in addition to a limitedenhancement in UTS values Consequently the quality in-dex values of the as-quenched (or solution heat-treated)alloys are remarkably higher than those in the as-castcondition

While the T6 heat treatment improves the UTS valuesconsiderably in comparison to the UTS values obtainedafter solution treatment it does so at the expense of theductility is trade-off between UTS and ductility valueswill certainly affect the quality index values and not nec-essarily in a positive way Likewise a similar behavior isnoted for the T5-treated alloys as well as can be inferredfrom Figure 4

It is evident that the superior ductility of the base alloyM1S is the main reason for the improved quality indices ofthis alloy in the majority of the conditions studied On theother hand the mutual enhancement in the strength andductility values of alloys M2S and M3S compared to those ofalloys M4S and M5S is responsible for the higher qualityindices of the former compared to those of the latter

e addition of Mn in alloy M3S results in transformingthe needles of the β-iron phase into the less detrimentalα-iron phase this favorable morphological change is be-lieved to improve the ductility and strength values of alloyM3S Whereas the structure of alloy M2S contains Ni-bearing phases with acicular morphologies and β-ironneedles that negatively affect the mechanical propertiesAccordingly the quality index values of alloy M3S are higherthan those of the 2wt Ni-containing alloy M2S in the as-cast SHT and T5 conditions In contrast the quality indexvalues of the T6-treated alloysM2S andM3S show a reversedbehavior according to the marginal variations in their tensileproperties and hence the quality index values

From Table 5 it is observable that the quality indexvalues calculated using Drouzyrsquos approach are higher thanthose obtained by the model developed by Caceres for alltreatment conditions per each alloy except for solution-treated conditions is can be attributed to the improvedductility of as-quenched conditions that will allow moreaccurate determination of the material parameters (K andn) us it would be advisable to calculate the quality indexvalues of solution-treated conditions using Caceresrsquo modelespecially for materials with low ductility at roomtemperature

322 Elevated-Temperature Tensile Testing Figure 5 revealsthe elevated-temperature tensile properties obtained at250degC for the alloys studied By tensile testing at 250degC allthe investigated alloys endure some softening owing to thepossible coarsening of the strengthening precipitates thatexist during tensile testing at room temperature (Figure 3)Figures 5(a) and 5(b) demonstrate that additions of Ni andMn in different amounts and combinations to the base alloyie alloys M2S through M5S slightly improve the strengthvalues of the base alloy in the range of 5ndash15MPa for both as-cast and T5-treated conditions e tight enhancement in

Advances in Materials Science and Engineering 9

strength values of the T5-treated conditions can be ascribed tothe limited variations in themicrostructural features of as-caststructures as well as to the low proportion of strengtheningprecipitates in the structure of T5-treated alloys

In regard to the ductility values in the as-cast conditionFigure 5(c) reveals that the highest ductility value is observedto be associated with the base alloy M1S with a value of

sim36 followed by the ductility of the Mn-containing alloysM3S andM5S and ending up with the lowest ductility valuesfor alloys M2S and M4S containing 2 and 4wt Ni re-spectively e higher ductility values of the as-cast Mn-containing alloys M3S andM5S can be attributed to the well-refined Si particles Table 4 and the transformation ofa considerable amount of β-Al5FeSi needles which may act

Table 5 Variation in average UTS YS El Qc and Q values of the alloys studied in as-cast SHT and T5- and T6-treated conditionsobtained at ambient temperature

Alloy Condition UTS(MPa)

YS(MPa)

Totalstrain ()

Plasticstrain () E (GPa) n K q Qc

(Equation (2))Q

(Equation (1))Difference

(QminusQc) (MPa)

M1S

As-cast 26086 19439 158 116 6266 018 58056 007 27788 29050 1262SHT 30034 20251 622 574 6250 017 57926 034 51236 41943 minus9293T5 28950 25875 094 048 6306 013 59169 004 21706 28543 6838T6 34195 32499 11075 056 6245 010 57691 006 28153 34860 6707

M2S

As-cast 32035 23585 163 116 6758 019 76378 006 34214 35219 1005SHT 32774 21261 320 270 6623 017 75932 016 53109 40343 minus12766T5 29997 27719 080 034 6564 015 70196 002 16710 28522 11812T6 36233 35157 080 024 6471 011 70779 002 19604 34816 15212

M3S

As-cast 32578 24572 176 126 6473 015 64889 008 35471 36255 784SHT 33475 20943 381 330 6447 012 64647 027 54926 42197 minus12729T5 31458 27939 098 049 6414 013 63449 004 23821 31310 7489T6 35701 35514 075 020 6432 008 62421 002 19202 33850 14648

M4S

As-cast 30440 22461 133 087 6610 020 83677 004 29364 32287 2923SHT 31232 20709 222 175 6656 018 82135 010 46959 36427 minus10532T5 27644 25414 071 031 6843 020 85707 002 9928 25451 15524T6 31598 31598 05705 011 6710 010 63474 001 7752 27941 20189

M5S

As-cast 29707 22659 127 083 6691 020 79201 004 27391 31280 3889SHT 29979 20664 199 154 6735 017 78035 009 43714 34462 minus9252T5 28461 27700 066 022 6474 015 72211 001 9720 25745 16025T6 31404 31404 056 011 6789 011 67764 001 4543 27632 23089

1

23

12

3

1 2

3

12

3

1 23

250

300

350

400

05 5

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

Drouzy quality index chart room temperature

M1SM2SM3S

M4SM5S

4 4

44

YS = 350 MPa

Q = 500 MPaQ = 450 MPa

Q = 350 MPa

Q = 250 MPa

Q = 300 MPa

Q = 400 MPa

YS = 250 MPa

4

1 as-cast2 SHT3 T54 T6

Figure 4 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast SHT and T5- and T6-treated conditions obtained at ambient temperature

10 Advances in Materials Science and Engineering

as crack initiators into the less detrimental α-Al15(MnFe)3Si2 phase with script-like andor sludge morphologies

e addition of Ni on the other hand lowers theductility values even for alloy M5S that contains 075wtMn when compared to alloy M3S which is Ni-free ereduction in ductility values of the as-cast Ni-containingalloys can be directly correlated to the presence of acicularNi-bearing phases with sharp edges such as Al3Ni Al9FeNiand Al3CuNi phases Variation in chemical compositionshas a limited eiexclect on the ductility values obtained at 250degCfor the T5-treated alloys since the maximum absolutediiexclerence in the ductility values of alloys M2S through M5Sis found to be sim044 Application of T5 and T6 heattreatments reduces the ductility observed in the as-castcondition e ductility values in the T6-treated conditionare generally lower than those obtained with T5 treatmentconditions

e application of the T6 heat treatment enhances thestrength values of as-cast conditions regardless the alloycomposition as shown in Figures 5(a) and 5(b) e en-hanced strength values of alloy M4S after T6 heat treatmentmay be attributed to the presence of δ-Al3CuNi and eutecticAl-Al3Ni phases that prove to contribute eiexclectively to theelevated-temperature strength of alloy M4S in spite ofa considerable amount of Cu that is consumed in formingthe δ-Al3CuNi phase which will certainly aiexclect the amount

of ne Al2Cu dispersoids formed which is consistent withthe ndings reported in references [38 49]

Interestingly alloys M3S (354 + 075wt Mn) and M4S(354 + 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the diiexclerent conditions ex-amined Moreover alloy M3S is considered to be morefavorable between the two since it exhibits higher ductilitythan that of the Ni-containing alloy M4S ese two alloysexhibit the best strength values (UTS and YS) in the T6-treated conditions among the investigated alloys whereasthe strength values of the other three alloys ie alloys M1SM2S and M5S are close to each other and lower than thestrength values obtained for alloys M3S and M4S bysim36MPa is observation would emphasize the advanta-geous role of adding Mn instead of Ni to enhance theelevated-temperature tensile properties along with its eco-nomic impact

Generally the closeness of the elevated-temperaturestrength values of the alloys studied can be credited tothe presence of 03 wt Zr in each alloy whereby theformation of the ne metastable L12-Al3Zr particles is ex-pected in the microstructures of all the alloys which in turnwill improve the alloy strength in a common manner

For elevated-temperature tensile properties the conceptof the quality index will be discussed according to theconcept of Drouzy et al [47] (Q) Table 6 demonstrates the

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditionsM1SM2SM3S

M4SM5S

(a)

M1SM2SM3S

M4SM5S

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditions

(b)

M1SM2SM3S

M4SM5S

005

115

225

335

445

AC T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

(c)

Figure 5 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in the as-cast solution heat-treated (SHT) and T5-and T6-treated conditions obtained at 250degC

Advances in Materials Science and Engineering 11

elevated-temperature tensile data along with the quality indexvalues (Q) of the alloys studied calculated using Equation (1)Figure 6 shows the quality chart obtained based on the cal-culations of Drouzy et al [47] As may be seen the qualityindex values obtained at 250degC do not show wide variation invalues as was observed in the case of the ambient-temperature data is limited variation can be understoodin light of the balanced variation in UTS and ductility valuesobtained at the elevated temperature of 250degC For examplethe base alloyM1S in the as-cast condition exhibits the highestductility value of 367 and a UTS value of 16995MPa whilethe lowest ductility is experienced by alloy M4S for the T6-treated condition with a value of 106 along with a UTSvalue of 25358MPa By calculating the quality indices of thesetwo conditions they revealQ values of 26395 and 25735MPafor as-cast M1S and T6-treated M4S respectively ose twoextreme conditions show that despite the considerable vari-ation in the UTS values on the one hand and ductility valueson the other for these two conditions the quality indices inboth cases remain almost unchanged due to the balancedtrade-off between the UTS and ductility values e relativelylowUTS and ductility values obtained at elevated temperature(250degC) for the T5-treated condition result in the T5-treatedalloys exhibiting minimum Q values among the conditionsstudied

Another interesting observation is that the quality indexvalues for alloys M2S and M3S in the T6-treated conditionare found to be the maximum for the alloys and conditionsstudied is observation highlights the enhanced charac-teristics of alloy M3S which contains 075wt Mn andemphasizes the positive influence of the high Mn-additionon the elevated-temperature tensile properties which arefound to be more or less comparable to those obtained withthe addition of 2 and 4wt Ni to the same base alloy

e favorable role of the blocky α-Al15(Fe Mn)3Si2phase termed as sludge particles in improving the tensileproperties of alloy M3S at 25degC and 250degC can be witnessed

from the fractograph of alloy M3S after testing at 250degCpresented in Figure 7 e sludge particles appear to retardthe propagation of the cracks developed in the other phaseswhich will subsequently enhance the mechanical propertiesof the respective alloy Yet another interesting observationmade from this figure is that while many of the intermetallicphase particles appear cracked as indicated by the solidarrows the sludge particles however are crack-freeWhereas the multiple cracked Ni-rich phases exist on thefracture surface of alloy M2S after testing at 250degC are be-lieved to contribute to the crack initiation process and hencedeteriorate the tensile properties of this alloy as witnessed inFigure 8

323 Hardness Values Figure 9 illustrates the variation inthe hardness values of the alloys as a function of the appliedheat treatment At first glance one can observe from Figure 9that the hardness values of different alloys show insignificantvariations for the same conditions For each alloy the peak-aged condition exhibits the highest hardness value among allconditions Also the tailored alloys ie M2S through M5Sshow better hardness values than those obtained for the basealloy in all the conditions studied

Variations in hardness values of the alloys in the as-castcondition can be attributed to the additions of Ni andor Mnmade to the base alloy M1S It was seen that additions of Niandor Mn in various amounts increased the volume frac-tions of intermetallic compounds considerably as listed inTable 3 e variations in hardness values follow the sametrend as variations in the percentage volume fraction ofintermetallic compounds us the base alloy M1S exhibitsthe lowest hardness value in the as-cast condition having thelowest volume fraction according to Table 3 and the highesthardness value of the same condition is associated with alloyM4S that has the highest volume fraction of intermetalliccompounds is observation highlights the effective role ofintermetallic compounds in enhancing the hardness values[19 50]

e dissolution of the strengthening elements over thecourse of the solution treatment reduces the hardness valuesin spite of the expected improved homogeneity in com-position and evolution of the eutectic silicon morphologyfollowing solution treatment is behavior emphasizes thecrucial role of intermetallic phases in influencing the me-chanical performance of alloys It is established that thehardness value of a specific alloy corresponds to the com-bination of the tensile yield strength and work-hardeningrate of the alloy [50 51] e order of the alloys studiedaccording to the hardness value in the as-quenched con-dition matches to a large extent their order with respect totheir yield strength in the same as-quenched condition(Figure 3)

Direct artificial aging following casting of test barsie T5-temper treatment introduces slight improvements inthe hardness values with respect to those obtained for the as-cast condition is can be attributed to the limited changesin the microstructure of the as-cast alloysbars followingdirect artificial aging without solution treatment e slight

Table 6 Variation in average UTS YS El and Q values of thealloys studied in as-cast and T5- and T6-treated conditions ob-tained at 250degC

Alloy Condition UTS(MPa)

YS(MPa) El Q (Equation (1))

M1SAs-cast 16995 15756 367 25465T5 17207 16151 202 21791T6 21765 21365 192 26014

M2SAs-cast 18632 17284 225 23915T5 19625 17885 160 22671T6 22372 22233 215 27365

M3SAs-cast 17576 16284 285 24399T5 18107 17745 161 21216T6 24874 24562 154 27668

M4SAs-cast 18053 16735 177 21757T5 18186 17913 132 19985T6 25358 25332 106 25735

M5SAs-cast 17648 16232 245 23492T5 19110 18402 176 22786T6 22209 22055 132 23996

12 Advances in Materials Science and Engineering

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

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strength values of the T5-treated conditions can be ascribed tothe limited variations in themicrostructural features of as-caststructures as well as to the low proportion of strengtheningprecipitates in the structure of T5-treated alloys

In regard to the ductility values in the as-cast conditionFigure 5(c) reveals that the highest ductility value is observedto be associated with the base alloy M1S with a value of

sim36 followed by the ductility of the Mn-containing alloysM3S andM5S and ending up with the lowest ductility valuesfor alloys M2S and M4S containing 2 and 4wt Ni re-spectively e higher ductility values of the as-cast Mn-containing alloys M3S andM5S can be attributed to the well-refined Si particles Table 4 and the transformation ofa considerable amount of β-Al5FeSi needles which may act

Table 5 Variation in average UTS YS El Qc and Q values of the alloys studied in as-cast SHT and T5- and T6-treated conditionsobtained at ambient temperature

Alloy Condition UTS(MPa)

YS(MPa)

Totalstrain ()

Plasticstrain () E (GPa) n K q Qc

(Equation (2))Q

(Equation (1))Difference

(QminusQc) (MPa)

M1S

As-cast 26086 19439 158 116 6266 018 58056 007 27788 29050 1262SHT 30034 20251 622 574 6250 017 57926 034 51236 41943 minus9293T5 28950 25875 094 048 6306 013 59169 004 21706 28543 6838T6 34195 32499 11075 056 6245 010 57691 006 28153 34860 6707

M2S

As-cast 32035 23585 163 116 6758 019 76378 006 34214 35219 1005SHT 32774 21261 320 270 6623 017 75932 016 53109 40343 minus12766T5 29997 27719 080 034 6564 015 70196 002 16710 28522 11812T6 36233 35157 080 024 6471 011 70779 002 19604 34816 15212

M3S

As-cast 32578 24572 176 126 6473 015 64889 008 35471 36255 784SHT 33475 20943 381 330 6447 012 64647 027 54926 42197 minus12729T5 31458 27939 098 049 6414 013 63449 004 23821 31310 7489T6 35701 35514 075 020 6432 008 62421 002 19202 33850 14648

M4S

As-cast 30440 22461 133 087 6610 020 83677 004 29364 32287 2923SHT 31232 20709 222 175 6656 018 82135 010 46959 36427 minus10532T5 27644 25414 071 031 6843 020 85707 002 9928 25451 15524T6 31598 31598 05705 011 6710 010 63474 001 7752 27941 20189

M5S

As-cast 29707 22659 127 083 6691 020 79201 004 27391 31280 3889SHT 29979 20664 199 154 6735 017 78035 009 43714 34462 minus9252T5 28461 27700 066 022 6474 015 72211 001 9720 25745 16025T6 31404 31404 056 011 6789 011 67764 001 4543 27632 23089

1

23

12

3

1 2

3

12

3

1 23

250

300

350

400

05 5

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

Drouzy quality index chart room temperature

M1SM2SM3S

M4SM5S

4 4

44

YS = 350 MPa

Q = 500 MPaQ = 450 MPa

Q = 350 MPa

Q = 250 MPa

Q = 300 MPa

Q = 400 MPa

YS = 250 MPa

4

1 as-cast2 SHT3 T54 T6

Figure 4 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast SHT and T5- and T6-treated conditions obtained at ambient temperature

10 Advances in Materials Science and Engineering

as crack initiators into the less detrimental α-Al15(MnFe)3Si2 phase with script-like andor sludge morphologies

e addition of Ni on the other hand lowers theductility values even for alloy M5S that contains 075wtMn when compared to alloy M3S which is Ni-free ereduction in ductility values of the as-cast Ni-containingalloys can be directly correlated to the presence of acicularNi-bearing phases with sharp edges such as Al3Ni Al9FeNiand Al3CuNi phases Variation in chemical compositionshas a limited eiexclect on the ductility values obtained at 250degCfor the T5-treated alloys since the maximum absolutediiexclerence in the ductility values of alloys M2S through M5Sis found to be sim044 Application of T5 and T6 heattreatments reduces the ductility observed in the as-castcondition e ductility values in the T6-treated conditionare generally lower than those obtained with T5 treatmentconditions

e application of the T6 heat treatment enhances thestrength values of as-cast conditions regardless the alloycomposition as shown in Figures 5(a) and 5(b) e en-hanced strength values of alloy M4S after T6 heat treatmentmay be attributed to the presence of δ-Al3CuNi and eutecticAl-Al3Ni phases that prove to contribute eiexclectively to theelevated-temperature strength of alloy M4S in spite ofa considerable amount of Cu that is consumed in formingthe δ-Al3CuNi phase which will certainly aiexclect the amount

of ne Al2Cu dispersoids formed which is consistent withthe ndings reported in references [38 49]

Interestingly alloys M3S (354 + 075wt Mn) and M4S(354 + 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the diiexclerent conditions ex-amined Moreover alloy M3S is considered to be morefavorable between the two since it exhibits higher ductilitythan that of the Ni-containing alloy M4S ese two alloysexhibit the best strength values (UTS and YS) in the T6-treated conditions among the investigated alloys whereasthe strength values of the other three alloys ie alloys M1SM2S and M5S are close to each other and lower than thestrength values obtained for alloys M3S and M4S bysim36MPa is observation would emphasize the advanta-geous role of adding Mn instead of Ni to enhance theelevated-temperature tensile properties along with its eco-nomic impact

Generally the closeness of the elevated-temperaturestrength values of the alloys studied can be credited tothe presence of 03 wt Zr in each alloy whereby theformation of the ne metastable L12-Al3Zr particles is ex-pected in the microstructures of all the alloys which in turnwill improve the alloy strength in a common manner

For elevated-temperature tensile properties the conceptof the quality index will be discussed according to theconcept of Drouzy et al [47] (Q) Table 6 demonstrates the

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditionsM1SM2SM3S

M4SM5S

(a)

M1SM2SM3S

M4SM5S

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditions

(b)

M1SM2SM3S

M4SM5S

005

115

225

335

445

AC T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

(c)

Figure 5 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in the as-cast solution heat-treated (SHT) and T5-and T6-treated conditions obtained at 250degC

Advances in Materials Science and Engineering 11

elevated-temperature tensile data along with the quality indexvalues (Q) of the alloys studied calculated using Equation (1)Figure 6 shows the quality chart obtained based on the cal-culations of Drouzy et al [47] As may be seen the qualityindex values obtained at 250degC do not show wide variation invalues as was observed in the case of the ambient-temperature data is limited variation can be understoodin light of the balanced variation in UTS and ductility valuesobtained at the elevated temperature of 250degC For examplethe base alloyM1S in the as-cast condition exhibits the highestductility value of 367 and a UTS value of 16995MPa whilethe lowest ductility is experienced by alloy M4S for the T6-treated condition with a value of 106 along with a UTSvalue of 25358MPa By calculating the quality indices of thesetwo conditions they revealQ values of 26395 and 25735MPafor as-cast M1S and T6-treated M4S respectively ose twoextreme conditions show that despite the considerable vari-ation in the UTS values on the one hand and ductility valueson the other for these two conditions the quality indices inboth cases remain almost unchanged due to the balancedtrade-off between the UTS and ductility values e relativelylowUTS and ductility values obtained at elevated temperature(250degC) for the T5-treated condition result in the T5-treatedalloys exhibiting minimum Q values among the conditionsstudied

Another interesting observation is that the quality indexvalues for alloys M2S and M3S in the T6-treated conditionare found to be the maximum for the alloys and conditionsstudied is observation highlights the enhanced charac-teristics of alloy M3S which contains 075wt Mn andemphasizes the positive influence of the high Mn-additionon the elevated-temperature tensile properties which arefound to be more or less comparable to those obtained withthe addition of 2 and 4wt Ni to the same base alloy

e favorable role of the blocky α-Al15(Fe Mn)3Si2phase termed as sludge particles in improving the tensileproperties of alloy M3S at 25degC and 250degC can be witnessed

from the fractograph of alloy M3S after testing at 250degCpresented in Figure 7 e sludge particles appear to retardthe propagation of the cracks developed in the other phaseswhich will subsequently enhance the mechanical propertiesof the respective alloy Yet another interesting observationmade from this figure is that while many of the intermetallicphase particles appear cracked as indicated by the solidarrows the sludge particles however are crack-freeWhereas the multiple cracked Ni-rich phases exist on thefracture surface of alloy M2S after testing at 250degC are be-lieved to contribute to the crack initiation process and hencedeteriorate the tensile properties of this alloy as witnessed inFigure 8

323 Hardness Values Figure 9 illustrates the variation inthe hardness values of the alloys as a function of the appliedheat treatment At first glance one can observe from Figure 9that the hardness values of different alloys show insignificantvariations for the same conditions For each alloy the peak-aged condition exhibits the highest hardness value among allconditions Also the tailored alloys ie M2S through M5Sshow better hardness values than those obtained for the basealloy in all the conditions studied

Variations in hardness values of the alloys in the as-castcondition can be attributed to the additions of Ni andor Mnmade to the base alloy M1S It was seen that additions of Niandor Mn in various amounts increased the volume frac-tions of intermetallic compounds considerably as listed inTable 3 e variations in hardness values follow the sametrend as variations in the percentage volume fraction ofintermetallic compounds us the base alloy M1S exhibitsthe lowest hardness value in the as-cast condition having thelowest volume fraction according to Table 3 and the highesthardness value of the same condition is associated with alloyM4S that has the highest volume fraction of intermetalliccompounds is observation highlights the effective role ofintermetallic compounds in enhancing the hardness values[19 50]

e dissolution of the strengthening elements over thecourse of the solution treatment reduces the hardness valuesin spite of the expected improved homogeneity in com-position and evolution of the eutectic silicon morphologyfollowing solution treatment is behavior emphasizes thecrucial role of intermetallic phases in influencing the me-chanical performance of alloys It is established that thehardness value of a specific alloy corresponds to the com-bination of the tensile yield strength and work-hardeningrate of the alloy [50 51] e order of the alloys studiedaccording to the hardness value in the as-quenched con-dition matches to a large extent their order with respect totheir yield strength in the same as-quenched condition(Figure 3)

Direct artificial aging following casting of test barsie T5-temper treatment introduces slight improvements inthe hardness values with respect to those obtained for the as-cast condition is can be attributed to the limited changesin the microstructure of the as-cast alloysbars followingdirect artificial aging without solution treatment e slight

Table 6 Variation in average UTS YS El and Q values of thealloys studied in as-cast and T5- and T6-treated conditions ob-tained at 250degC

Alloy Condition UTS(MPa)

YS(MPa) El Q (Equation (1))

M1SAs-cast 16995 15756 367 25465T5 17207 16151 202 21791T6 21765 21365 192 26014

M2SAs-cast 18632 17284 225 23915T5 19625 17885 160 22671T6 22372 22233 215 27365

M3SAs-cast 17576 16284 285 24399T5 18107 17745 161 21216T6 24874 24562 154 27668

M4SAs-cast 18053 16735 177 21757T5 18186 17913 132 19985T6 25358 25332 106 25735

M5SAs-cast 17648 16232 245 23492T5 19110 18402 176 22786T6 22209 22055 132 23996

12 Advances in Materials Science and Engineering

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

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Submit your manuscripts atwwwhindawicom

as crack initiators into the less detrimental α-Al15(MnFe)3Si2 phase with script-like andor sludge morphologies

e addition of Ni on the other hand lowers theductility values even for alloy M5S that contains 075wtMn when compared to alloy M3S which is Ni-free ereduction in ductility values of the as-cast Ni-containingalloys can be directly correlated to the presence of acicularNi-bearing phases with sharp edges such as Al3Ni Al9FeNiand Al3CuNi phases Variation in chemical compositionshas a limited eiexclect on the ductility values obtained at 250degCfor the T5-treated alloys since the maximum absolutediiexclerence in the ductility values of alloys M2S through M5Sis found to be sim044 Application of T5 and T6 heattreatments reduces the ductility observed in the as-castcondition e ductility values in the T6-treated conditionare generally lower than those obtained with T5 treatmentconditions

e application of the T6 heat treatment enhances thestrength values of as-cast conditions regardless the alloycomposition as shown in Figures 5(a) and 5(b) e en-hanced strength values of alloy M4S after T6 heat treatmentmay be attributed to the presence of δ-Al3CuNi and eutecticAl-Al3Ni phases that prove to contribute eiexclectively to theelevated-temperature strength of alloy M4S in spite ofa considerable amount of Cu that is consumed in formingthe δ-Al3CuNi phase which will certainly aiexclect the amount

of ne Al2Cu dispersoids formed which is consistent withthe ndings reported in references [38 49]

Interestingly alloys M3S (354 + 075wt Mn) and M4S(354 + 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the diiexclerent conditions ex-amined Moreover alloy M3S is considered to be morefavorable between the two since it exhibits higher ductilitythan that of the Ni-containing alloy M4S ese two alloysexhibit the best strength values (UTS and YS) in the T6-treated conditions among the investigated alloys whereasthe strength values of the other three alloys ie alloys M1SM2S and M5S are close to each other and lower than thestrength values obtained for alloys M3S and M4S bysim36MPa is observation would emphasize the advanta-geous role of adding Mn instead of Ni to enhance theelevated-temperature tensile properties along with its eco-nomic impact

Generally the closeness of the elevated-temperaturestrength values of the alloys studied can be credited tothe presence of 03 wt Zr in each alloy whereby theformation of the ne metastable L12-Al3Zr particles is ex-pected in the microstructures of all the alloys which in turnwill improve the alloy strength in a common manner

For elevated-temperature tensile properties the conceptof the quality index will be discussed according to theconcept of Drouzy et al [47] (Q) Table 6 demonstrates the

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditionsM1SM2SM3S

M4SM5S

(a)

M1SM2SM3S

M4SM5S

100

150

200

250

300

AC T5 T6

Stre

ngth

(MPa

)

Treatment conditions

(b)

M1SM2SM3S

M4SM5S

005

115

225

335

445

AC T5 T6

el

onga

tion

to fr

actu

re

Treatment conditions

(c)

Figure 5 Variation in average (a) UTS (b) YS and (c) El values of the alloys studied in the as-cast solution heat-treated (SHT) and T5-and T6-treated conditions obtained at 250degC

Advances in Materials Science and Engineering 11

elevated-temperature tensile data along with the quality indexvalues (Q) of the alloys studied calculated using Equation (1)Figure 6 shows the quality chart obtained based on the cal-culations of Drouzy et al [47] As may be seen the qualityindex values obtained at 250degC do not show wide variation invalues as was observed in the case of the ambient-temperature data is limited variation can be understoodin light of the balanced variation in UTS and ductility valuesobtained at the elevated temperature of 250degC For examplethe base alloyM1S in the as-cast condition exhibits the highestductility value of 367 and a UTS value of 16995MPa whilethe lowest ductility is experienced by alloy M4S for the T6-treated condition with a value of 106 along with a UTSvalue of 25358MPa By calculating the quality indices of thesetwo conditions they revealQ values of 26395 and 25735MPafor as-cast M1S and T6-treated M4S respectively ose twoextreme conditions show that despite the considerable vari-ation in the UTS values on the one hand and ductility valueson the other for these two conditions the quality indices inboth cases remain almost unchanged due to the balancedtrade-off between the UTS and ductility values e relativelylowUTS and ductility values obtained at elevated temperature(250degC) for the T5-treated condition result in the T5-treatedalloys exhibiting minimum Q values among the conditionsstudied

Another interesting observation is that the quality indexvalues for alloys M2S and M3S in the T6-treated conditionare found to be the maximum for the alloys and conditionsstudied is observation highlights the enhanced charac-teristics of alloy M3S which contains 075wt Mn andemphasizes the positive influence of the high Mn-additionon the elevated-temperature tensile properties which arefound to be more or less comparable to those obtained withthe addition of 2 and 4wt Ni to the same base alloy

e favorable role of the blocky α-Al15(Fe Mn)3Si2phase termed as sludge particles in improving the tensileproperties of alloy M3S at 25degC and 250degC can be witnessed

from the fractograph of alloy M3S after testing at 250degCpresented in Figure 7 e sludge particles appear to retardthe propagation of the cracks developed in the other phaseswhich will subsequently enhance the mechanical propertiesof the respective alloy Yet another interesting observationmade from this figure is that while many of the intermetallicphase particles appear cracked as indicated by the solidarrows the sludge particles however are crack-freeWhereas the multiple cracked Ni-rich phases exist on thefracture surface of alloy M2S after testing at 250degC are be-lieved to contribute to the crack initiation process and hencedeteriorate the tensile properties of this alloy as witnessed inFigure 8

323 Hardness Values Figure 9 illustrates the variation inthe hardness values of the alloys as a function of the appliedheat treatment At first glance one can observe from Figure 9that the hardness values of different alloys show insignificantvariations for the same conditions For each alloy the peak-aged condition exhibits the highest hardness value among allconditions Also the tailored alloys ie M2S through M5Sshow better hardness values than those obtained for the basealloy in all the conditions studied

Variations in hardness values of the alloys in the as-castcondition can be attributed to the additions of Ni andor Mnmade to the base alloy M1S It was seen that additions of Niandor Mn in various amounts increased the volume frac-tions of intermetallic compounds considerably as listed inTable 3 e variations in hardness values follow the sametrend as variations in the percentage volume fraction ofintermetallic compounds us the base alloy M1S exhibitsthe lowest hardness value in the as-cast condition having thelowest volume fraction according to Table 3 and the highesthardness value of the same condition is associated with alloyM4S that has the highest volume fraction of intermetalliccompounds is observation highlights the effective role ofintermetallic compounds in enhancing the hardness values[19 50]

e dissolution of the strengthening elements over thecourse of the solution treatment reduces the hardness valuesin spite of the expected improved homogeneity in com-position and evolution of the eutectic silicon morphologyfollowing solution treatment is behavior emphasizes thecrucial role of intermetallic phases in influencing the me-chanical performance of alloys It is established that thehardness value of a specific alloy corresponds to the com-bination of the tensile yield strength and work-hardeningrate of the alloy [50 51] e order of the alloys studiedaccording to the hardness value in the as-quenched con-dition matches to a large extent their order with respect totheir yield strength in the same as-quenched condition(Figure 3)

Direct artificial aging following casting of test barsie T5-temper treatment introduces slight improvements inthe hardness values with respect to those obtained for the as-cast condition is can be attributed to the limited changesin the microstructure of the as-cast alloysbars followingdirect artificial aging without solution treatment e slight

Table 6 Variation in average UTS YS El and Q values of thealloys studied in as-cast and T5- and T6-treated conditions ob-tained at 250degC

Alloy Condition UTS(MPa)

YS(MPa) El Q (Equation (1))

M1SAs-cast 16995 15756 367 25465T5 17207 16151 202 21791T6 21765 21365 192 26014

M2SAs-cast 18632 17284 225 23915T5 19625 17885 160 22671T6 22372 22233 215 27365

M3SAs-cast 17576 16284 285 24399T5 18107 17745 161 21216T6 24874 24562 154 27668

M4SAs-cast 18053 16735 177 21757T5 18186 17913 132 19985T6 25358 25332 106 25735

M5SAs-cast 17648 16232 245 23492T5 19110 18402 176 22786T6 22209 22055 132 23996

12 Advances in Materials Science and Engineering

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

CorrosionInternational Journal of

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Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

elevated-temperature tensile data along with the quality indexvalues (Q) of the alloys studied calculated using Equation (1)Figure 6 shows the quality chart obtained based on the cal-culations of Drouzy et al [47] As may be seen the qualityindex values obtained at 250degC do not show wide variation invalues as was observed in the case of the ambient-temperature data is limited variation can be understoodin light of the balanced variation in UTS and ductility valuesobtained at the elevated temperature of 250degC For examplethe base alloyM1S in the as-cast condition exhibits the highestductility value of 367 and a UTS value of 16995MPa whilethe lowest ductility is experienced by alloy M4S for the T6-treated condition with a value of 106 along with a UTSvalue of 25358MPa By calculating the quality indices of thesetwo conditions they revealQ values of 26395 and 25735MPafor as-cast M1S and T6-treated M4S respectively ose twoextreme conditions show that despite the considerable vari-ation in the UTS values on the one hand and ductility valueson the other for these two conditions the quality indices inboth cases remain almost unchanged due to the balancedtrade-off between the UTS and ductility values e relativelylowUTS and ductility values obtained at elevated temperature(250degC) for the T5-treated condition result in the T5-treatedalloys exhibiting minimum Q values among the conditionsstudied

Another interesting observation is that the quality indexvalues for alloys M2S and M3S in the T6-treated conditionare found to be the maximum for the alloys and conditionsstudied is observation highlights the enhanced charac-teristics of alloy M3S which contains 075wt Mn andemphasizes the positive influence of the high Mn-additionon the elevated-temperature tensile properties which arefound to be more or less comparable to those obtained withthe addition of 2 and 4wt Ni to the same base alloy

e favorable role of the blocky α-Al15(Fe Mn)3Si2phase termed as sludge particles in improving the tensileproperties of alloy M3S at 25degC and 250degC can be witnessed

from the fractograph of alloy M3S after testing at 250degCpresented in Figure 7 e sludge particles appear to retardthe propagation of the cracks developed in the other phaseswhich will subsequently enhance the mechanical propertiesof the respective alloy Yet another interesting observationmade from this figure is that while many of the intermetallicphase particles appear cracked as indicated by the solidarrows the sludge particles however are crack-freeWhereas the multiple cracked Ni-rich phases exist on thefracture surface of alloy M2S after testing at 250degC are be-lieved to contribute to the crack initiation process and hencedeteriorate the tensile properties of this alloy as witnessed inFigure 8

323 Hardness Values Figure 9 illustrates the variation inthe hardness values of the alloys as a function of the appliedheat treatment At first glance one can observe from Figure 9that the hardness values of different alloys show insignificantvariations for the same conditions For each alloy the peak-aged condition exhibits the highest hardness value among allconditions Also the tailored alloys ie M2S through M5Sshow better hardness values than those obtained for the basealloy in all the conditions studied

Variations in hardness values of the alloys in the as-castcondition can be attributed to the additions of Ni andor Mnmade to the base alloy M1S It was seen that additions of Niandor Mn in various amounts increased the volume frac-tions of intermetallic compounds considerably as listed inTable 3 e variations in hardness values follow the sametrend as variations in the percentage volume fraction ofintermetallic compounds us the base alloy M1S exhibitsthe lowest hardness value in the as-cast condition having thelowest volume fraction according to Table 3 and the highesthardness value of the same condition is associated with alloyM4S that has the highest volume fraction of intermetalliccompounds is observation highlights the effective role ofintermetallic compounds in enhancing the hardness values[19 50]

e dissolution of the strengthening elements over thecourse of the solution treatment reduces the hardness valuesin spite of the expected improved homogeneity in com-position and evolution of the eutectic silicon morphologyfollowing solution treatment is behavior emphasizes thecrucial role of intermetallic phases in influencing the me-chanical performance of alloys It is established that thehardness value of a specific alloy corresponds to the com-bination of the tensile yield strength and work-hardeningrate of the alloy [50 51] e order of the alloys studiedaccording to the hardness value in the as-quenched con-dition matches to a large extent their order with respect totheir yield strength in the same as-quenched condition(Figure 3)

Direct artificial aging following casting of test barsie T5-temper treatment introduces slight improvements inthe hardness values with respect to those obtained for the as-cast condition is can be attributed to the limited changesin the microstructure of the as-cast alloysbars followingdirect artificial aging without solution treatment e slight

Table 6 Variation in average UTS YS El and Q values of thealloys studied in as-cast and T5- and T6-treated conditions ob-tained at 250degC

Alloy Condition UTS(MPa)

YS(MPa) El Q (Equation (1))

M1SAs-cast 16995 15756 367 25465T5 17207 16151 202 21791T6 21765 21365 192 26014

M2SAs-cast 18632 17284 225 23915T5 19625 17885 160 22671T6 22372 22233 215 27365

M3SAs-cast 17576 16284 285 24399T5 18107 17745 161 21216T6 24874 24562 154 27668

M4SAs-cast 18053 16735 177 21757T5 18186 17913 132 19985T6 25358 25332 106 25735

M5SAs-cast 17648 16232 245 23492T5 19110 18402 176 22786T6 22209 22055 132 23996

12 Advances in Materials Science and Engineering

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

increase in the hardness values in the T5-treated conditionemphasizes the positive role of employing a high solidifi-cation rate in the casting process e high solidification rateallows for partial solubility of Cu and Mg in the α-Al matrixsuch that subsequent artificial aging will precipitate a limitedamount of strengthening precipitates to produce themarginal increase in hardness values observed

With respect to the peak-aged condition the hardnessvalues of alloys M2S through M5S are almost identicalapproaching sim100HRF whereas the hardness value of thebase alloy for the same T6-treated condition is sim96HRF isvariation can be ascribed to the combined effect of thestrengthening precipitates and intermetallic compounds in

the four alloyse improvement in hardness of the base alloyin the T6-treated condition compared to the as-cast case ismainly attributed to the effect of the strengthening pre-cipitates formed after the T6 treatment because of the lowvolume fraction of intermetallic phases observed in the mi-crostructure of the base alloy as listed in Table 3 (namelysim251 in the as-cast condition and 111 in the as-quenchedcondition) which is too low compared to the other alloys

324 Impact Properties e impact bars used in the presentstudy were not notched based on three considerations (i) theexpected low toughness of 354-type alloys (ii) increasing the

12

3

12

3

12

3

12

3

12

3

100

150

200

250

300

1 10

Ulti

mat

e ten

sile s

tren

gth

(MPa

)

Elongation to fracture ()

M1SM2SM3S

M4SM5S

Drouzy quality index chart elevated temperature

YS = 250 MPa

YS = 150 MPa

YS = 50 MPa

Q = 300 MPa

Q = 350 MPa

Q = 400 MPa

Q = 150

Q = 200 MPa

Q = 250 MPa

Figure 6 Drouzy quality chart representing the relation between the UTS and the percent elongation to fracture values of the alloys studiedin the as-cast and T5- and T6-treated conditions obtained at 250degC

Sludge particles

Spectrum 3

(a) (b)

Figure 7 SEM images of T6-treatedM3S alloy after testing at 250degC (a) BSE image showing various cracked intermetallic phases and crack-free sludge particles and (b) EDS spectrum corresponding to the point of interest in (a)

Advances in Materials Science and Engineering 13

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

measurement accuracy by excluding uncertainties associatedwith machining of notches and (iii) emphasizing the eiexclectsof microstructural constituents

e variation in the toughness values of the alloysstudied as a function of the applied heat treatment is dis-played in Figure 10 It is evident that values of the totalabsorbed energy for the alloys studied are relatively low inthe as-cast T5-treated and T6-treated conditions comparedto those obtained in the solution heat-treated conditions

e morphology of the eutectic silicon particles and thevolume fraction of intermetallic compounds [52] present aresupposed to determine the impact properties of the as-castalloys studied in the present investigation It is worthmentioning that the sphericity and roundness parameters(in percentage) of the eutectic silicon particles in the as-castcondition did not vary substantially with respect to the alloycomposition as shown in Table 4 erefore the only

parameter aiexclecting the impact properties of the as-castalloys is the presence of intermetallic compounds As canbe inferred from Figure 10 the order of alloys according tothe absorbed energy during impact testing matches that withrespect to the volume fraction of intermetallic compoundsshown in Table 3 us it can be deduced that increasing thevolume fraction of intermetallic compounds will increase theamount of absorbed energy and hence improve the impactproperties

ermal-modication of eutectic silicon particles asso-ciated with solution heat treatment can contribute positivelyto the impact properties by (i) producing more roundededges of the Si particles instead of the relatively sharp edgesobtained in as-cast conditions and hence better resistance tocracks initiation and propagation resulting in highertoughness values and (ii) producing well-separated siliconparticles through the fragmentation of the interconnected

Spectrum 2

(a) (b)

Figure 8 SEM images of T6-treatedM2S alloy after testing at 250degC (a) BSE image showingmicrocracks associated with Ni-rich phases and(b) EDS spectrum corresponding to the point of interest in (a)

70

75

80

85

90

95

100

AC SHT T5 T6

Har

dnes

s (H

RF)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 9 Variation in Rockwell hardness value (HRF) as a func-tion of heat treatment conditions for the alloys studied

0

5

10

15

20

25

AC SHT T5 T6

Tota

l im

pact

ener

gy (J

)

Treatment condition

Alloy M1SAlloy M2SAlloy M3S

Alloy M4SAlloy M5S

Figure 10 Variation in total impact energy value as a function ofheat-treatment conditions for the alloys studied

14 Advances in Materials Science and Engineering

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

CorrosionInternational Journal of

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Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

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Analytical ChemistryInternational Journal of

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ScienticaHindawiwwwhindawicom Volume 2018

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Advances in Condensed Matter Physics

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High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

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ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

fibrous silicon structure present in the Sr-modified as-caststructures which will make available greater areas of theductile α-Al matrix and hence improve the impact properties[50] In light of the aforementioned points the impactproperties of the alloys studied in the as-cast conditionsubstantially improved by applying solution heat treatmentat 495degC for 5 hours e increase in the total absorbedenergy values for each alloy after solution treatment are asfollows (i) 15 J for the base alloy M1S (ii) 11 J for alloy M2S(iii) 12 J for alloy M3S (iv) 9 J for alloy M4S and (v) 8 J foralloy M5S

e impact properties of an alloy are directly related toits ductility Figure 11 illustrates the relationship between theimpact properties and ductility values of the alloys studiede relationship between these two properties shows a lineartrend with a high goodness of fitting represented by the highvalue of R2 e order of alloys with respect to their impactenergy values (Figure 10) matches with the order of thealloys with respect to the ductility values (Figure 3(c)) ob-tained from room temperature tensile testing

e impact properties of the investigated alloys in T5-and T6-treated conditions are close in values and lower thanthe values obtained in the as-cast and as-quenched condi-tions respectively For the alloy studied the presence of fineprecipitates in T5- and T6-treated conditions promotes theinitiation of fine cracks which will eventually reduce theimpact properties [53] is would explain the reducedimpact properties observed in the T5- and T6-treatedconditions of the alloys studied

e Al2Cu phase particles seem to control the impactproperties of the alloys studied rather than the eutecticsilicon particles due to the following observations eimpact properties of the investigated alloys have no sig-nificant variations with respect to the condition studiedie the total energies absorbed by the five alloys in the as-cast condition are close in their values the same for the T5-and T6-treated conditions is may be ascribed to the samecopper content in the studied alloys and the existence ofAl2Cu-phase particles in their microstructures On the otherhand the total absorbed energy values vary widely for the as-quenched alloys is wide variation can be attributed to thedissolution of Al2Cu phase particles during the course ofsolution treatment so that the impact properties are nolonger dependent on the Al2Cu particles but on other mi-crostructural features reported to have noticeable differ-ences Similar observations have been previously reportedfor copper containing alloys by Paray et al [53]

4 Conclusions

is article discussed the effects of the addition of transitionelements and applied heat treatments on the microstructuralcharacteristics of test bars of Zr-containing 354-type Al-Si-Cu-Mg cast alloys including volume fractions of in-termetallic compounds formed and the eutectic siliconparticle characteristics followed by evaluating the ambient-and elevated-temperature tensile properties hardness andimpact properties e most important findings are asfollows

(1) e proposed additions and heat treatments enhancethe overall mechanical performance of the alloysnamely the ambient- and elevated-temperaturetensile properties hardness and impact properties

(2) For the Mn-containing alloys the improvement inproperties results from the formation of polygonalsludge particles in the form of blocky α-Al15(FeMn)3Si2 alongside the script-like α-iron phase whichresists crack propagations

(3) Blocky sludge particles prove to be beneficial to themechanical properties through blocking the propa-gation of cracks and stand crack-free after the tensiletesting till fracture

(4) Alloys M3S (354 + 075wt Mn) and M4S (354+ 4wt Ni) exhibit the highest and almost identicalstrength values at 250degC for the different conditionsexamined

(5) Addition of 075wt Mn to the base alloy is con-sidered more favorable than adding 4wt Ni sinceit results in higher ductility values (cf 154 in alloyM3S and 106 in M1S for T6-treated conditionstested at 250degC) this finding is of considerableeconomic benefits

(6) e variations in hardness values and impactproperties followed the same trend as variations inthe percentage volume fraction of intermetalliccompounds

(7) e impact properties of the alloys are highlyinfluenced by the Al2Cu phase particles rather thanthe eutectic silicon particles

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that they have no conflicts of interest

R2 = 08865

10

12

14

16

18

20

22

0 1 2 3 4 5 6 7

Tota

l abs

orbe

d en

ergy

(J)

elongation

M4S

M1S

M3S

M2S

M5S

Figure 11 Correlation between impact energy and ductility valuesof the alloys studied in the solution-heat treated condition

Advances in Materials Science and Engineering 15

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

Acknowledgments

e authors would like to thank Prof Agnes-Marie Samuelfor her efforts in editing the language of this article and DrEmad Elgallad for his efforts in SEM investigations

References

[1] R Lemon and C Howle ldquoPremium strength aluminumcasting alloys 354 and 359rdquo Trans AFS Transactions vol 71p 465 1963

[2] J G Kaufman and E L Rooy Aluminum Alloy CastingsAmerican Foundry Society Columbus OH USA 2004

[3] J E Hatch Aluminum Properties and Physical MetallurgyASM International Geauga County OH USA 1984

[4] H Ammar Influence of Metallurgical Parameters on theMechanical Properties and Quality Indices of Al-Si-Cu-Mg andAl-Si-Mg Casting Alloys Universite du Quebec a ChicoutimiSaguenay Canada 2010

[5] AFS Society and D L Zalensas Aluminum Casting Tech-nology American Foundrymenrsquos Society Schaumburg ILUSA 1993

[6] A H Volume Properties and Selection Nonferrous Alloys andSpecial-Purpose Materials ASM International GeaugaCounty OH USA 1990

[7] G H Garza-Elizondo Effect of Ni Mn Zr and Sc Additions onthe Performance of Al-Si-Cu-Mg Alloys ProQuest Disserta-tions Publishing Ann Arbor MI USA 2016

[8] C Caceres I L Svensson and J Taylor ldquoStrength-ductilitybehaviour of Al-Si-Cu-Mg casting alloys in T6 temperrdquo In-ternational Journal of Cast Metals Research vol 15 no 5pp 531ndash543 2003

[9] A Mohamed and F Samuel ldquoA review on the heat treatmentof Al-Si-CuMg casting alloysrdquo in Heat Treatment-Conventional and Novel Applications p 229 IntechopenLondon UK 2012

[10] J Hernandez-Sandoval G Garza-Elizondo A SamuelS Valtiierra and F Samuel ldquoe ambient and high tem-perature deformation behavior of AlndashSindashCundashMg alloy withminor Ti Zr Ni additionsrdquo Materials and Design vol 58pp 89ndash101 2014

[11] A Mohamed and F Samuel ldquoMicrostructure tensile prop-erties and fracture behavior of high temperature AlndashSindashMgndashCu cast alloysrdquo Materials Science and Engineering Avol 577 pp 64ndash72 2013

[12] K E Knipling Development of a Nanoscale Precipitation-Strengthened Creep-Resistant Aluminum Alloy ContainingTrialuminide Precipitates Northwestern University EvanstonIL USA 2006

[13] S K Shaha Development and Characterization of CastModified Al-Si-Cu-Mg Alloys for Heat Resistant Power TrainApplications Ryerson University Toronto Canada 2015

[14] D Srinivasan and K Chattopadhyay ldquoMetastable phaseevolution and hardness of nanocrystalline AlndashSindashZr alloysrdquoMaterials Science and Engineering A vol 304 pp 534ndash5392001

[15] Z Yin Q Pan Y Zhang and F Jiang ldquoEffect of minor Sc andZr on the microstructure andmechanical properties of AlndashMgbased alloysrdquo Materials Science and Engineering A vol 280no 1 pp 151ndash155 2000

[16] J Hernandez-Sandoval Improving the Performance of 354Type Alloy Universite du Quebec a Chicoutimi SaguenayCanada 2010

[17] K E Knipling D C Dunand and D N Seidman ldquoCriteriafor developing castable creep-resistant aluminum-basedalloysndasha reviewrdquo Zeitschrift fur Metallkunde vol 97 no 3pp 246ndash265 2006

[18] R Mahmudi P Sepehrband and H Ghasemi ldquoImprovedproperties of A319 aluminum casting alloy modified with ZrrdquoMaterials Letters vol 60 no 21 pp 2606ndash2610 2006

[19] E E Elgallad Effect of additives on the mechanical propertiesand machinability of a new aluminum-copper base alloyUniversite du Quebec a Chicoutimi Saguenay Canada 2010

[20] N Belov A Alabin D Eskin and V Istomin-KastrovskiildquoOptimization of hardening of AlndashZrndashSc cast alloysrdquo Journalof materials science vol 41 no 18 pp 5890ndash5899 2006

[21] D Srinivasan and K Chattopadhyay ldquoNon-equilibriumtransformations involving L1 2-Al 3 Zr in ternary Al-X-Zralloysrdquo Metallurgical and Materials Transactions A vol 36no 2 pp 311ndash320 2005

[22] G Gustafsson T orvaldsson and G Dunlop ldquoe in-fluence of Fe and Cr on the microstructure of cast Al-Si-MgalloysrdquoMetallurgical Transactions A vol 17 no 1 pp 45ndash521986

[23] L F Mondolfo Manganese in Aluminum Alloys e Man-ganese Centre Neuilly sur Seine France 1978

[24] A Couture ldquoIron in aluminum casting alloys-a literaturesurveyrdquo International Cast Metals Journal vol 6 no 4pp 9ndash17 1981

[25] W Bonsack ldquoDiscussion on the effect of minor alloying el-ements on aluminum casting alloysrdquo ASTM Bulletin vol 117p 45 1942

[26] J Iglessis C Frantz and M Gantois ldquoConditions de for-mation des phases de fer dans les alliages Al-Si de puretecommercialerdquo Memoires Scientifiques de la Revue deMetallurgie vol 73 no 4 pp 237ndash242 1977

[27] G H Garza-Elizondo A M Samuel S Valtierra andF H Samuel ldquoPhase precipitation in transition metal-containing 354-type alloysrdquo International Journal of Mate-rials Research vol 108 no 2 pp 108ndash125 2017

[28] S Shabestari ldquoe effect of iron and manganese on theformation of intermetallic compounds in aluminumndashsiliconalloysrdquo Materials Science and Engineering A vol 383 no 2pp 289ndash298 2004

[29] A Joenoes and J Gruzleski ldquoMagnesium effects on the mi-crostructure of unmodified and modified Al-Si alloysrdquo CastMetals vol 4 no 2 pp 62ndash71 1991

[30] R Dunn and W Dickert ldquoMagnesium effect on the strengthof A380 0 and 3830 aluminum die casting alloysrdquo Die CastEngineering vol 19 pp 2ndash20 1975

[31] W Chen Y Wang J Qiang and C Dong ldquoBulk metallicglasses in the Zr-Al-Ni-Cu systemrdquo Acta Materialia vol 51no 7 pp 1899ndash1907 2003

[32] W Yuying L Xiangfa J Binggang and H ChuanzhenldquoModification effect of Nindash38 wt Si on Alndash12 wt Si alloyrdquoJournal of Alloys and Compounds vol 477 no 1 pp 118ndash1222009

[33] J Jorstad ldquoUnderstanding Sludgerdquo Die Cast Engineeringvol 30 no 6 p 30 1986

[34] J Gobrecht Segregation par Gravite du Fer du Manganese etdu Chrome dans les Alliages Al-Si de Fonderie Fonderievol 367 pp 171ndash173 1977

[35] F Samuel A Samuel and H Liu ldquoEffect of magnesiumcontent on the ageing behaviour of water-chilled Al-Si-Cu-Mg-Fe-Mn (380) alloy castingsrdquo Journal of Materials Sciencevol 30 no 10 pp 2531ndash2540 1995

16 Advances in Materials Science and Engineering

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

[36] A M Samuel A Pennors C Villeneuve F H SamuelH W Doty and S Valtierra ldquoEffect of cooling rate and Sr-modification on porosity and Fe-intermetallics formation inAl-65 Si-35 Cu-Fe alloysrdquo International Journal of CastMetals Research vol 13 no 4 pp 231ndash253 2000

[37] R Molina P Amalberto and M Rosso ldquoMechanical char-acterization of aluminium alloys for high temperature ap-plications part 1 Al-Si-Cu alloysrdquo Metallurgical Science andTechnology vol 29 no 1 p 5 2011

[38] Y Li Y Yang Y Wu L Wang and X Liu ldquoQuantitativecomparison of three Ni-containing phases to the elevated-temperature properties of AlndashSi piston alloysrdquo MaterialsScience and Engineering A vol 527 no 26 pp 7132ndash71372010

[39] D Lee J Park and S Nam ldquoEnhancement of mechanicalproperties of AlndashMgndashSi alloys by means of manganese dis-persoidsrdquo Materials science and technology vol 15 no 4pp 450ndash455 1999

[40] A Farkoosh X G Chen and M Pekguleryuz ldquoInteractionbetween molybdenum and manganese to form effective dis-persoids in an AlndashSindashCundashMg alloy and their influence oncreep resistancerdquo Materials Science and Engineering Avol 627 pp 127ndash138 2015

[41] SW Nam and D H Lee ldquoe effect of Mn on themechanicalbehavior of Al alloysrdquo Metals and Materials Internationalvol 6 no 1 pp 13ndash16 2000

[42] D S Park and S W Nam ldquoEffects of manganese dispersoidon the mechanical properties in Al-Zn-Mg alloysrdquo Journal ofMaterials Science vol 30 no 5 pp 1313ndash1320 1995

[43] J Catherall and R Smart ldquoe effects of nickel in aluminium-silicon eutectic alloysrdquo Metallurgia vol 79 no 476pp 247ndash250 1969

[44] T Takahashi A Kamio and Y Kojima ldquoEffects of Ni and Feaddition on various properties in heat resisting aluminumcasting alloysrdquo Journal of Japan Institute of Light Metalsvol 23 no 1 pp 26ndash32 1973

[45] N Belov D Eskin and N Avxentieva ldquoConstituent phasediagrams of the AlndashCundashFendashMgndashNindashSi system and their ap-plication to the analysis of aluminium piston alloysrdquo ActaMaterialia vol 53 no 17 pp 4709ndash4722 2005

[46] T Savaskan and Y Alemdag ldquoEffect of nickel additions on themechanical and sliding wear properties of Alndash40Znndash3Cualloyrdquo Wear vol 268 no 3 pp 565ndash570 2010

[47] M Drouzy S Jacob and M Richard ldquoInterpretation oftensile results by means of quality index and probable yieldstrength-application to Al-Si7 mg foundry alloys-francerdquoInternational Cast Metals Journal vol 5 no 2 pp 43ndash501980

[48] S Jacob ldquoQuality index in prediction of properties of alu-minum castings-a reviewrdquo in Proceedings of Transactions ofthe American Foundry Society and the One Hundred FourthAnnual Castings Congress Pittsburgh PA USA 2000

[49] A Farkoosh M Javidani M Hoseini D Larouche andM Pekguleryuz ldquoPhase formation in as-solidified and heat-treated AlndashSindashCundashMgndashNi alloys thermodynamic assessmentand experimental investigation for alloy designrdquo Journal ofAlloys and Compounds vol 551 pp 596ndash606 2013

[50] A Mohamed Effect of Additives on the Microstructure andMechanical Properties of Aluminum-silicon Alloys ProQuestAnn Arbor MI USA 2008s

[51] J Barresi Z Chen C Davidson et al ldquoCasting of aluminiumalloy componentsrdquoMaterials Forum vol 20 pp 53ndash70 1996

[52] T Kobayashi and M Niinomi ldquoFracture Toughness and fa-tigue characteristics of aluminum casting alloyrdquo Journal ofJapan Institute of Light Metals vol 41 pp 398ndash405 1991

[53] F Paray B Kulunk and J Gruzleski ldquoImpact properties ofAl-Si foundry alloysrdquo International Journal of Cast MetalsResearch vol 13 no 1 pp 17ndash37 2000

Advances in Materials Science and Engineering 17

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom

CorrosionInternational Journal of

Hindawiwwwhindawicom Volume 2018

Advances in

Materials Science and EngineeringHindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Journal of

Chemistry

Analytical ChemistryInternational Journal of

Hindawiwwwhindawicom Volume 2018

ScienticaHindawiwwwhindawicom Volume 2018

Polymer ScienceInternational Journal of

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

Advances in Condensed Matter Physics

Hindawiwwwhindawicom Volume 2018

International Journal of

BiomaterialsHindawiwwwhindawicom

Journal ofEngineeringVolume 2018

Applied ChemistryJournal of

Hindawiwwwhindawicom Volume 2018

NanotechnologyHindawiwwwhindawicom Volume 2018

Journal of

Hindawiwwwhindawicom Volume 2018

High Energy PhysicsAdvances in

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawiwwwhindawicom

The Scientific World Journal

Volume 2018

TribologyAdvances in

Hindawiwwwhindawicom Volume 2018

Hindawiwwwhindawicom Volume 2018

ChemistryAdvances in

Hindawiwwwhindawicom Volume 2018

Advances inPhysical Chemistry

Hindawiwwwhindawicom Volume 2018

BioMed Research InternationalMaterials

Journal of

Hindawiwwwhindawicom Volume 2018

Na

nom

ate

ria

ls

Hindawiwwwhindawicom Volume 2018

Journal ofNanomaterials

Submit your manuscripts atwwwhindawicom