CHARACTERIZATION OF PARTICULATE-...

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International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 9, September 2017, pp. 178–190, Article ID: IJCIET_08_09_020

Available online at http://http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=8&IType=9

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

CHARACTERIZATION OF PARTICULATE-

REINFORCED ALUMINIUM 7075 / TIB2

COMPOSITES

P. Pradeep, P. S. Samuel Ratna Kumar

Assistant Professor, Department of Mechanical Engineering,

Kumaraguru College of Technology, Coimbatore, India

Daniel Lawrence I

Faculty, Department of Mechanical Engineering,

Anna University Regional Campus Madurai, India

Jayabal S

Assistant Professor, Department of Mechanical Engineering,

A.C College of Engg and Tech, Karaikudi, India

ABSTRACT

Aluminum-based metal matrix composite (MMC) materials are used in the design

of ground transportation vehicles and aircraft structures due to its light weight and

high strength to weight ratio. Compared with conventional, unreinforced alloys,

composite materials usually exhibit higher strength, both at ambient and elevated

temperatures, as well as good fatigue strength and wear resistance. Stir casting

process is one of the most effective methods for manufacturing Metal matrix

composites (MMCs) due to its high volume reinforcement and fairly uniform

distribution. This work deals with the production of Aluminium 7075 alloy reinforced

with TiB2 particle. The composites were fabricated by three varying the volume % of

Titanium diboride (TiB2) particles. The mechanical properties and microstructure

analysis are identified from the experimental results and the ability of the

manufactured aluminium matrix composite from the different reinforcements.

Keywords: Metal matrix composite, Reinforcement, Microstructure, Mechanical

properties

Cite this Article: P. Pradeep, P. S. Samuel Ratna Kumar, Daniel Lawrence I and

Jayabal S, Characterization of Particulate-Reinforced Aluminium 7075 / Tib2

Composites, International Journal of Civil Engineering and Technology, 8(9), 2017,

pp. 178–190.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=9

P. Pradeep, P. S. Samuel Ratna Kumar, Daniel Lawrence I and Jayabal S


1. INTRODUCTION

Nowadays metal matrix composites are widely used in engineering application for the

replacement of heavy metals and also the development of metal matrix composites increase

the efficiency of the product and cost. The primary use of high-strength aluminum alloys is in

aircraft construction; the airframe of modern aircraft is approximately 80 percent aluminum

by weight (Marceau, 1994). Traditionally, the structural aluminum alloys in aircraft have been

2024 in damage-critical areas and 7075 in strength-critical areas (Starke and Staley, 1996).

The goal of aircraft designers to improve durability and save weight has led to the

development of new aluminum alloys that provide improved combinations of specific

strength, durability, and damage tolerance. The tighter controls on chemistry and processing

parameters may cause an increase in the cost of the material, but production applications of

improved alloys show that this cost can be offset by benefits in performance or durability. The

comparative study on hot dynamic compaction and quasi-static hot pressing of Al7075 is

mechanically milled with 0%, 5%, and 10% compositions of SiC. The maximum level of

kinetic energy distributed to specimen may result increase in impact strength therefore fine

particles are easily merged leading to reduction of porosity and increase in green density.

Enhancing the dislocation density by strengthening mechanism increases the hardness by 20%

with respect to monolithic material for dynamically compacted specimen. The uniform

distribution of micro hardness noticed in hot static compaction and also increases strength

with increase in SiC reinforcement [1]

. Specific wear rate of Al7075 with 7% of SiC and 3%

of graphite acts as a solid lubricant this composition is prepared by stir casting method. The

results of hybrid composites compared with the unreinforced alloy with various parameters

like loads, sliding speed, and sliding distance. The Al7075 hybrid composite prepared by stir

casting method at 600rpm with 1% of mg further it is heat treated and solution treated at

490oC for 2hours then this samples is also undergoes water quenching and aging process at

120oC for 20hours.The test conducted in pin on disc testing machine at ambient temperature

without lubrication and the structure of the samples were examined by micro structural testing

such as SEM, XRD, EDX and RSM. The specific wear rate decrease as sliding speed

increases with above mentioned parameters at low speed and low load condition. Graphite

acts as solid lubricant by creating a protective layer between pin and counter face increases

wear resistance [2]

. The reduction of particle size from micro level to nano level in Al 7075

reinforced with 2% and 5% of ZrO2 by applying milling using only balls gives better results.

The structure of ZrO2 gets destabilized from tetragonal to monoclinic were maximum level of

ZrO2 takes more time to achieve dispersion and also cubic structure is noticed which can be

stabilized by adding oxides such as yttria Y2O3 for minimum amount. The powder which is

obtained from grinding undergoes annealing process at 415oC for 48 hours in felisa furnace.

The particle size reduced from 37µm to 108nm by continuous milling for 140 hours further

increase in time doesn’t tend to any changes [3]

. This study deals with the mechanical behavior

of Al7075 reinforced with 1%, 3%, and 5% of nano size Alumina (Al2O3) alloy by

mechanical alloying to produce high performance composites. The structure, grain size and

crystallite size were studied by taking SEM, TEM and XRD test along with this lattice strain

are predicted by Williamson –Hall equation. The increase in Al2O3 leads to reduction in

fracture toughness which may also reduce particle size. The maximum hardness obtained at

5% of Al2O3 is 204HB whereas the tensile strength rises from 276 to 443MPa which is 60.5%

higher than base matrix [4]

.

The super plasticity of material can be fabricated by friction stir processing. Three

different profiles were selected such as square, pentagon, and hexagon. The poor joint

strength in Al7075 exhibits hot cracking this can be overcome by using this alloy without

joint. Three Stir process samples were produced at 1500 rpm rotational speed with the

Characterization of Particulate-Reinforced Aluminium 7075 / Tib2 Composites


temperature maintained approximately 305oC. The hardness of the materials is 100, 116, and

115 for square, pentagon and hexagon respectively. The microstructure without cavitations

was observed only in square pin which also exhibit super plastic behaviour by achieving

227% of uniform elongation [5]

. Machinability of TiB2 particle reinforced in Al7050 has been

investigated. PCD tool sustains least tool wear due to hardness and wear resistance with

Minimum surface roughness was observed. Al7056-T6 alloy blended with 6% of TiB2 with

grain size ranges from 50 to 200nm was machined in conventional lathe and surface

roughness and morphology tested by SEM, XRD and contact surface roughness tester

accordingly. Surface roughness of tools decreases with cutting speed and decrease of feed

speed were TiB2 particles give better surface quality. Better surface roughness can be

achieved by implementing PCD and PCBN due to higher hardness also sustains least tool

wear [6]

. The knuckle joint made up of Al/TiC, unreinforced alloy and graphite has been

evaluated by finding the load bearing capacity for automobile applications. Aluminium LM6

mixed with TiC material by stir casting method with a speed of 900 rpm for 10min at 800oC.

Micro structural shows more Al3Ti and Al4C3 blocks formed at 750oC which gets reduced

with rise in temperature [7]

. The hardness of the Al 6061–TiB2–Gr composite was increased

mainly due to the weight percentage of the TiB2 and Gr. The hardness and tensile strength

decreases with increase in graphite content and addition of TiB2 raises strength value to some

extent. TiB2 material increases density with increase in hardness. The acoustic emission

technique (non-destructive test) is used to measure acoustic energy released during

deformation process and early crack detection with UTM interfaced to acoustic emission

recorder in wave form which helps to detect failure during manufacturing [8]

.

The study revealed that the creep properties of β-phase titanium alloy with the addition of

neutral element Zr were investigated through powder metallurgy. The pre-alloyed powder

with higher aluminium content with 5 different alloy compositions Ti–45Al–5Nb– (1, 2, 3, 4,

5) Zr–0.2B–0.2C were blended at 120oC for 2000rpm. The formation of a Zr-enriched γ phase

at colony boundaries was promoted by elemental Zr additions, which was an effect of the

specific powder metallurgy processing of these alloys. The results shows Zr will increase the

hardenss and creep resistance [9]

. Fine grained beta titanium alloy (Ti-40Nb) was successfully

prepared by mechanical alloying of TiH2 and Nb by spark plasma sintering which increases

hardness with increase in temperature. The MA also led to the lowering of dehydrogenation

temperature of hydride particles. Sintering of MAed powders under low temperature

conditions (1223 K, & 1373 K) resulted in the fine-grained heterogeneous microstructure

consisting of a, b, and unreacted pure Nb phase. Brittle TiH2, unlike pure titanium powder,

avoids agglomeration, cold welding, and sticking to the milling balls and vials during ball

milling or mechanical alloying process, leading to almost 100% recovery of milled powders [10]

. The energy efficient surface composite is produced by Friction stir processing and Al

7075 reinforced with B4C shows maximum level of increase in wear resistance with 40-70%

of increase in hardness. The matrix with more B4C particle shows higher coefficient of

friction as 0.6 which enhances resistance to wear [11]

. The piston material is made up of Al-Si

alloy reinforced with 4% of TiB2 and the alloy treated at temperature of 350oC. Fractographic

morphology studies were done which shows the changes in the material from phase brittle to

ductile with rise in temperature from 25-350oC were separated TiB2 particles leads to crack

[12]. The reciprocating wear behavior of AL7075/SiC was compared with 6061Al/Al2O3

composites. The Composite pins are prepared with three different weight percentages of SiC

and Al2O3 particles with size of 36 μm. Hardness of these composites increases with increase

in wt. % of reinforcement. However, the impact strength decreases with increase in wt. % of

SiC and Al2O3 reinforcement content [13]

.

The mechanical behavior, modeling and optimization of wear parameters on hybrid

composites reinforced with B4C and graphite. Aluminium alloy 6061 and 7075 were



reinforced with 10 wt. % of B4C and 5 wt. % of graphite through liquid casting technique. For

improving wettability of B4C with aluminium alloy at below 850 ºC, Potassium Hexa Fluro

Titanate (K2TiF6) flux is added as same quantity of B4C. The addition of Graphite in

aluminium matrix, leads to reduction in hardness and flexural strength to overcome this, one

of the most promising ceramic material boron carbide (B4C) is included. The high hardness,

increased % of elongation and wear resistance obtained in the AA 7075 hybrid composite

compared to the AA 6061 alloy [14]

. Microstructure and mechanical properties of high volume

content SiCp / 7075Al composites is prepared by pressure infiltration method. Contrary to

other SiCp / Al composites prepared by the pressure infiltration method, an interface layer

was witnessed between SiC particles and Al matrix. Furthermore, high-resolution

transmission electron microscopy (HRTEM) observation specified that this interface layer

was coherent/semi-coherent with that of the SiC particles. Al7075 with 45 vol. % of SiCp

reveals high tensile strength (630 MPa) and micro-ductility. High density dislocations were

found around SiC / Al interface in SiCp / 7075Al composite after water-quenching and aging

treatment. Fine dispersed nano - ή phases were observed after the aging treatment. Compared

to aged SiCp/2024Al composite, the aged SiCp / 7075Al composite showed an increase of

about 200% in the tensile strain and 90% in the tensile strength, respectively. It is conjectured

that nano-ή phases in the Al matrix significantly contributed to the strengthening effect while

the interface layer between SiC and Al matrix might be beneficial aspect to the strength and

plasticity composite [15]

. This paper investigates manufacturing of Aluminium Alloy (Al7075)

reinforced with SiC replacing the existing components that are manufactured with Aluminium

oxide reinforcement due to their higher wear resistance and creep resistance applications. The

present work was focused on the manufacturing of gear with AMMC material using stir

casting process. Since, we know that gear plays a dynamic role in manufacturing sector to

transmit power. The particle size of the selected material is 20µm were preheated before

introducing into the molten metal. Stirring were accomplished for 10 min at 400rpm.Post

processing temperature was 720oC. It was observed that there is an increase in strength and

hardness by 10% compared to Al6061.Significantly SiC contributes an improving of wear

resistance in Al7075/SiC composites [16]

.

This study shows the influence of rutile (TiO2) content on wear and micro hardness

characteristics of aluminium-based hybrid composites are synthesized by powder metallurgy.

The proposed content of TiO2 (0, 4%, 8%, 12% of mass fraction) was blended to Al−15%SiC

composites through powder metallurgy process. The mean diameter of aluminium particle

chosen based on ASTM B−214 is 37μm and TiO2 particles with an average diameter of 44μm,

respectively. The powders were preheated to 200 °C before compaction. Powders were cold

compacted at 800 MPa in a uniaxial press. Optical micrographs showed the uniform

distribution of TiO2 throughout the matrix. Quantitative results indicate better wear resistance

and micro hardness than the unreinforced Al−SiC composites and the base matrix with the

increase of TiO2 content. SEM images unveil that high wear resistance is recognized to high

dislocation density of deformed planes and high hardness of TiO2. The micrograph of the

wear debris collected for the hybrid composites shows reduced mean size as the content of

TiO2 (rutile) increases [17]

. The Corrosion of Al7075 during the production of aeronautical

components: Influence of process parameters at the deburring / adjustment stage on the

development of surface defects in parts. The results showed that the degreasing bath

concentration and temperature, the immersion time of the aluminium parts in the degreasing

solution, and the use of solvent pre-cleaning had no significant influence on the quantity of

surface defects. The degreasing process includes different steps, solvent cleaning, water

washing, alkaline degreasing, and drying. The surface defects found were classified and

quantified considering their frequency and size. The corrosiveness of the degreaser was

shown to least time of usage [18]

. Comparatively studied the composites reinforced with SiC



and TiB2. Two specimens were fabricated by adding 10 wt % of SiC and TiB2 with

aluminium (6061Al-T6) metal matrix fabricated by using stir casting route with bottom

pouring technique. A silicon carbide particle of average size of 25 microns is selected as

reinforcement for the first specimen. Titanium diboride particles size of 10 microns is added

as reinforcement for the second specimen. The wt % of reinforcement for both specimens is

10 %. SiC particles were preheated at 1000°C for 2 hours to improve the wettability by

removing the absorbed hydroxide and other gases. TiB2 is preheated up to 200°C. The furnace

temperature was raised to 750°C to melt the matrix completely. At this stage the preheated

SiC particles were added and mixed. Mg 2gms is added in order to increase the wettability.

Mechanical stirring was carried out for 15 min at 350 rpm average stirring speed. Tensile

strength has been observed that, TiB2 composite is 30 % higher than SiC composite and also

hardness value of SiC is higher than TiB2 composites [19]

. The Effect of Ti content and stirring

time on microstructure and mechanical behavior of Al-B4C composites were investigated. A

simple way to fabricate tri-modal Al-B4C-Al3Ti composites was proposed and efforts have

been made to correlate microstructure evolution with mechanical response of the composites.

Commercially available pure aluminium (99.7%), Al-5 wt% Ti and B4C powders with

diameter from 2 to 50 mm were the raw materials. After removing the slag from the melt, B4C

particles were gradually added as reinforcement. The mechanical stirrer was hold at 500 rpm

after all the B4C powders were incorporated and the stable vortex lasted for 10 min to 20 min

respectively. Consequently, increasing Al3Ti volume fraction and particle size, growing Tib2

layer interface together resulted in gradual increase in tensile strength and the transformation

in particle arrangement was responsible for the leap in strength and more uniform particle

spatial distribution was achieved [20]

. The reinforcement of different volume % of

molybdenum particles with Al6082 produced by friction stir processing to improve ductility

of material. Rolled Aluminium alloy plates with 50mm breath and 100mm length were

machined at the middle using EDM to create groove and Mo particles (25 µm) were packed

with various volume fraction. It is identified that the Mo particles are distributed

homogenously in the composite which improves the tensile strength without compromising

on ductility [21]

.

2. MATERIALS AND METHODOLOGY

2.1 Preparation of composites

Al7075 alloy has been selected as the matrix and the chemical composition and mechanical

properties of the matrix material is given in the Table 1 and Table 2 respectively. The

reinforcing material was taken TiB2 with 4%, 6% and 8% weight respectively. The chemical

composition and the mechanical properties of the Titanium diboride are given in the Table 3

and Table 4 respectively. The metal was first melted above the super heating 700°C in

Titanium diboride is added in the graphite crucible under a cover of nitrogen gas by using an

electrical resistance-heating furnace. During this process, the molten metal was well agitated

by a mechanical stirrer to create turbulence motion. The depth of the immersed impeller was

approximately 2/3 of the height of the molten metal from the bottom of the crucible and the

speed of the stirrer maintained at 500 rpm. The detail of composite composition, particle size

and their respective densities are illustrated in Table5. During mechanical stirring 1 wt. %

magnesium was also added to increase the wettability of reinforcing particles. The presence of

magnesium in aluminum matrix composite not only has the beneficial effects of alloying but

also reduces the surface tension and better wetting dispersion respectively.



Table 1 Chemical Composition of Al7075

Element Percentage

(%)

Cu 1.2-2

Cr 0.18- 0.28

Mn 0.3

Mg 2.1-2.9

Si 0.4

Ti 0.2

Zn 5.1-6.1

Fe 0.5

Al balance

Table 2 Mechanical properties of Al 7075

Density 2.81g/cc

Hardness, Vickers 175 HV

Ultimate Tensile

Strength 572MPa

Tensile Yield Strength 503MPa

Modulus of Elasticity 71.7GPa

Thermal Conductivity 130 W/m-K

Melting Point 477-635oC

Table 3 Chemical Composition of TiB2

Element Titanium Boron

Content

% 68.88 31.15

Table 4 Mechanical properties of Titanium diboride (TiB2)

Density 4.52 g/cc

Melting Point 2970o C

Modulus of Rupture 410-448

Hardness 1800 knop

Elastic modulus 510 -575 Gpa

Poisson's Ratio 0.1 - 0.15

Volume resistivity at

20°C 15x10

-6 ohm.cm

Thermal conductivity 25 W/m.K

Table 5 Details of Reinforcement (TiB2)

Reinforcement Grain Size(µm) Density(g/cc) Purity (%)

TiB2 20 4.52 99

The microstructure of the Al 7075 matrix and TiB2 reinforced material is obtained by

scanning electron microscope and displayed figure 1 (a) and (b). The pin on disc shows in

figure 2. Wear is erosion or sideways displacement of material from its derivative and original

position on a solid surface performed by the action of another surface. It is related to



interactions between surfaces and specifically the removal and deformation of material on a

surface because of mechanical action of the opposite surface. Wear of metals occurs by the

plastic displacement of surface and near-surface material and by the detachment of particles

that form wear debris. The size of the generated particles may vary from millimeter range

down to an ion range. This process may occur by contact with other metals, nonmetallic

solids, flowing liquids, or solid particles or liquid droplets entrained in flowing gasses. The

pin dimensions are 8mm diameter and 32mm length. The high carbon high Chromium disc

was selected with diameter of 165mm and hardness 62HRC

Figure 1 (a) SEM image of Al7075; (b) SEM image of TiB2

Figure 2 PIN – ON – DISC SETUP

2.2 Experimental procedure

Steps to be followed in order to conduct the experiment are:

1. Place the test metal disc on DC motor.

2. Place the pin over the disc.

3. Run the motor at full speed and ON the range meter.

4. Place the weights in the pan and observe the wear pattern on disc made by pin.

Simultaneously, note the reading from range meter.

5. Take the reading from the graph.

Dry sliding wear test was conducted using pin on disk tester according to ASTM G99

standard. The composites are in the form of cylindrical pins of 10mm diameter and 20 mm

length. Pin surface were polished using emery papers with various grid sizes

(200,400,600,800), EN31 hardened steel of 62 HRC with diameter of 165mm and surface

roughness of 0.8µm.All the test are conducted in atmosphere conditions. The wear parameters

selected for the experiment were sliding speed in meter per second (m/s), load in Newton (N)

and sliding distance in meter (m). The non-linear behavior of the process parameters, if exists,

can only be revealed when more than two levels of the parameters are investigated. Therefore,



each parameter was analyzed at three levels and process parameters along with their values at

three levels are given in Table 6 by design of experiments.

3. RESULTS AND DISCUSSION

3.1 Hardness

Hardness test was conducted by Micro Vickers testing machine using 136o included angle

inverted diamond pyramid indenter. The applied load is 0.5 Kgf for a dwell time of 10sec.

Vickers / Micro hardness test procedure as per ASTM E-384, EN ISO 6507, and ASTM E-92

standard specifies making indentation with a range of loads using a diamond indenter which is

then measured and converted to a hardness value. For this purpose as long as test samples are

carefully and properly prepared, the Vickers / Micro hardness method is considered to be very

useful for testing on a wide type of materials, including metals, composites, ceramics, or

applications such as testing foils, measuring surface of a part, testing individual

microstructures, or measuring the depth of case hardening by sectioning a part and making a

series of indentations. Two types of indenters are generally used for the Vickers test family, a

square base pyramid shaped diamond for testing in a Vickers hardness tester and a narrow

rhombus shaped indenter for a Knoop hardness tester. The hardness results for the different

mentioned reinforcements are tabulated in Table 7 by Micro Vickers hardness.

3.2 Effect of Reinforcement on Microstructure Analysis

3.2.1 Optical Microscope

The “As polished” matrix of the metal matrix composite produced by stir casting matrix

shows the distortion of the Composite particles. The particles are uniformly distributed in the

matrix.

Figure 3 (a) 96% Al7075 with 4 % TiB2; (b) 94% Al7075with 6 % TiB2

(c) 92% Al7075 with 8% TiB2



Photo-1 shows the distribution of the particles which are very small but in photo-2 the

particles are clearly resolved in the matrix. The matrix shows no voids/pores between the

grains.

Microstructures of the different fabricated composites are observed by optical microscope

and the images shows the distribution of reinforcement on the matrix material. The 4 wt. % of

TiB2 has uniformly disturbed on the Aluminum composites and mostly particles are in grain

boundaries, 6wt. % of TiB2 has some agglomeration of particles. But 8 wt. % of TiB2 particles

are uniformly disturbed on the Aluminum composites. The better microstructures are

identified in 8 wt. % of TiB2.

3.3 Effect of Reinforcement on Wear Analysis

The Tribological properties of the composites were assessed using a pin-on-disc under

elevated temperature conditions. The fabricated composite specimens have a cylindrical pin

form of 8mm diameter and 50mm height. Pin surface was prepared by grinding against 1000-

grit silicon carbide paper and cleaning with acetone. Initial and final weight of the pins was

weighed using a highly sensitive electronic balance having an accuracy of 0.0001gm to

determine the mass loss.

Weight loss WL (gm.) = WI-WF

Wear volume loss VL (mm3) = WL/ P

Wear rate R (mm3/N-m) = VL/ (N*D)

Where P is the density of pin material, N the normal load (N), D the sliding distance (m),

WI the initial weight of the pin (gm.) and WF is the final weight of the pin (gm.).

It is observed that the wear and friction behaviour of MMCs having aluminum as matrix

strongly depends on the particles used for reinforcements, its size and volume fraction of

particles. The coefficients of friction of the metal matrix composites are high, if the rate of

reinforcement particle in MMC is low and besides this, the wear resistance increases with

increasing volume fraction of reinforcing particulates. If the particulates used for

reinforcement bonded well to the matrix, the wear resistance of the composite increases

continuously with increase in the volume fraction of reinforcement particles and the critical

volume fraction mostly depends on the load and temperature applied during the wear test. The

experiments are conducted by using taguchi experiments approach. Due to the wide ranges of

parameters selected, it has been decided to use orthogonal array design. The wear parameters

selected for the experiment where load is in Newton (N), sliding speed in meter per second

(m/s) and temperature (°C). The experimental results are tabulated in Table 8 and the

ANOVA analysis results are showed in Table 9.



Figure 4 (a) Wear rate about sliding distance and reinforcement;

(b) Wear rate about load and speed

#Table 6 Wear test parameters and levels

S.NO LOAD

(N)

SPEED

(m/s)

DISTANCE

(m)

REINFORCEMENT

(%)

1 10 1.2 500 4

2 20 1.4 1000 6

3 30 1.6 1500 8

Table 7 Hardness results for the different reinforcements of TiB2

S. No AA7075 + TiB2

COMP/TRIAL 4 % 6 % 8%

1 94.4 105.5 125

2 109.2 100.3 128

3 105.2 110.2 130.5

4 106.2 116.6 138.5

5 105.2 117.6 142.1

MEAN 104.4 110.04 132.82

Table 8 The variable parameters and their results

Run Load (N) Speed (m/s) Sliding

distance (m)

Wt. % of

reinforcement Wear rate

1 10 1.4 1000 6 1.45

2 20 1.4 1500 4 1.758

3 30 1.6 1000 4 2.012

4 20 1.6 500 6 1.55

5 10 1.6 1500 8 1.35

6 30 1.2 1500 6 2.156

7 10 1.2 500 4 1.752

8 20 1.2 1000 8 1.648

9 30 1.4 500 8 2.123



Table 9 ANOVA Analysis and significant

Source Sum of

Squares Mean Square F Value

p-value

Prob > F Suggestion

Model 0.604263 0.15106579 8.8147901 0.0290 Significant

A-Load 0.50402 0.50402017 29.409914 0.0056 -

B-Speed 0.069123 0.06912267 4.0333539 0.1150 -

C-Distance 0.00432 0.00432017 0.2520846 0.6420 -

D-

Reinforcment 0.0268 0.02680017 1.5638077 0.2793 -

Residual 0.068551 0.01713776 - - -

Cor Total 0.672814 - - - -

Figure 4 (c) Wear rate about load and reinforcement

The Model F-value of 8.81 implies the model is significant. There is only a 2.90% chance

that a "Model F-Value" this large could occur due to noise. Values of "Prob > F" less than

0.0500 indicate model terms are significant. The figure 7, 8 and 9 are showed the relationship

between the variable parameters and their responsible wear rate. The increasing wt. % of

reinforcements are in decreased the wear rate.

4. CONCLUSION

This investigation Aluminium matrix composites fabricated for the Aerospace applications.

The Hardness, Microstructure and Wear are evaluvated. Al7075 reinforced with TiB2

composite specimens are prepared using stir casting technique. Hardness of composites is

gradually increased with increasing the reinforcement on the base alloy and the maximum

hardness achieved at 8 Wt. % of the TiB2 reinforced Aluminium matrix. The micro structure

shows the aluminium particles are uniformly distributed in the maximum percentage of

reinforced composite of 8 Wt. % the least value of the wear rate obtained from the 8 Wt. % of

TiB2 reinforced composite and the Speed and the sliding distance are in maximum with the

minimum of load. Specific wear rate decreases as the sliding speed increases up to transition

speed (1.6 m/s) and load, due to work hardening of specimen surface. The developed response

surface model has been validated experimentally and exhibit low value of error up to 7%.



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