Post on 06-Sep-2020
INVESTIGATION OF MICROSTRUCTURE FEATURES OF AlMg9 ALLOY
Zdenka Zovko Brodarac, Jožef Medved2, Primož Mrvar2 1 University of Zagreb Faculty of Metallurgy, Aleja narodnih heroja 3, Sisak, Croatia 2 University of Ljubljana Faculty of Natural Sciences and Engineering, Aškerčeva cesta 12, Ljubljana, Slovenia
OUTLINE
INTRODUCTION - AIM OF INVESTIGATION:
Importance and application of Al-Mg alloys
Al-Mg(-Si) system
EXPERIMENTAL:
Materials and methodology
RESULTS AND DISCUSSION:
Thermodynamic analysis
Metallographic analysis
Microstructure features analysis
Correlation of microstructure features to cooling rate
CONCLUSION
INTRODUCTION
WHY Al-Mg ALLOYS? low density high strength and hardness achieved by natural aging significant corrosion resistance in see water and atmosphere dimensional stability excellent weldability suitability for recycling
APPLICATION! tool plates
complex thin-walled shapes - rotor limbs
cooling plates used by mechanical
processing
instruments housing
ship parts
gun frames
optical systems
architecture and decorative purposes
INTRODUCTION
Aluminum corner of the Al – Mg phase diagram
Solid phase distribution in aluminum reach
corner of the Al – Mg – Si diagram.
Reaction T / °C
Compositions of liquid
Mg / mass. % Si /mass.%
L→ αAl + Mg2Si (quasibinary section) 595 8,15 7,75
L→ αAl + (Si) + Mg2Si 555 4,96 12,95
L→ αAl + Mg2Si + Al8Mg5 449 32,2 0,37
Invariant reactions in ternary alloys of the Al-Mg-Si system
Al-Mg SYSTEM Al-Mg-Si SYSTEM
Characterization of microstructure features of AlMg9 alloy in different cooling condition based on:
influence of different cooling rate on the significant temperature of phase transformations during solidification and grain size of the AlMg9
alloy
phase analysis, surface area, elongation and number of grains per surface area (NA) of the corresponding microstructure related to the
cooling rates.
INTRODUCTION
THE AIM OF THIS INVESTIGATION:
EXPERIMENTAL
CASTING OF THE TEST SAMPLES -melting in the graphite pot into the induction furnace till approximately 730 °C -melt casting into the measuring cells to achieve different cooling rates in the sample:
cronning cell (standard Quick Cup equipped by the thermoelement Ni-CrNi) grey iron permanent mould of the conic shape.
CHEMICAL ANALYSIS: charge material - ingots of the quality EN 51200 (AlMg9) alloy chemical composition - spectrometer Spectro DIN 31051
THERMODYNAMICAL MODELING OF THE PHASE DIAGRAM OF THE AlMg9 ALLOY BY THE SOFTWARE Thermo-Calc (TCW 5.0) phase equilibrium - software ThermoCalc (TCW 5.0) - enable calculation of the thermodynamical stability of particular phases related to the chosen initial conditions: temperature, pressure and chemical compositions, on the foundation of the data basis.
EXPERIMENTAL
METALOGRAPHIC ANALYSIS -samples: taken in instant neighboring of the thermoelement positions, prepared by standard methods of grinding and polishing:
microstructural examination - etched in diluted HF grain size determination - electrolytic etching: U=23V, t=40s, Barker reagent
-optical microscope Olympus BX61, equipped by the automatic image analysis (Analysis®MaterialsResearchLab) -scanning electron microscope JEOL 5610 + EDS
SIMPLE AND SIMULTANEOUS THERMAL ANALYSIS -data acquisition:
Simple TA - measuring card DAQ Pad-MI0-16XE-50 and analysis by software LabView 7.0; cooling curves - drawn and processed by software Origin 7.0 Simultaneous TA - DSC by the instrument Netzsch STA 449C Jupiter; sample heating till 720 °C, heating/cooling rate 10 K/min
Marks:
- MIA – Multiple Image
Analysis; (100x)
- R – outer edge of the
sample;
- S – middle of the sample,
position where
thermoelement was placed;
Magnification:
1 – 50x; 2 – 100x; 3 – 200x;
4 – 500x; 5 – 1000x
- X – series of the
microphotographs recording;
(100x)
SAMPLE FROM THE CRONNING CELL
SAMPLE FROM THE CONIC MOULD
EXPERIMENTAL
CHEMICAL ANALYSIS
Compared chemical composition of the examined multicomponent technical alloy AlMg9 with those prescribed by norm EN 1706:2010 .
Alloy Element Si Fe Cu Mn Mg Cr Ni Zn Ti
Investigated AlMg9 w
mass.%
1,212 0,757 0,0543 0,2966 10,08 0,0034 0,0086 0,0231 0,0904
EN AC-AlMg9 2,5 1,0 0,10 0,55 8,0 -10,5
0,25 0,20
RESULTS AND DISCCUSSION
THERMODYNAMICAL MODELING OF THE PHASE DIAGRAM OF AN AlMg9 ALLOY BY THE ThermoCalc (TCW 5.0) SOFTWARE
PHASES EVALUATION:
Al13Fe4
Al6Mn
αAl
Mg2Si
AlMg-β
ZnMgMnFeCuSiTL %25,2%5%90,1%29,2%5%54,325,658 = 597,3 °C
ZnMgMnFeCuSiT SiMgE %76,10%23,2%96,7%57,0%3%17,14009,4102, = 559,5 °C
-initial condition: T = 743 °C, p = 105 MPa, default chemical composition
Thermodynamical calculation of the equilibrium phase diagram of examined AlMg9 alloy. Polytherm section of the
equilibrium phase diagram.
RESULTS AND DISCCUSSION
RESULTS AND DISCCUSSION
Dependence of the significant temperature of phase transformations from the cooling rate of the AlMg9 alloy.
RESULTS OF SIMPLE AND SIMULTANEOUS THERMAL ANALYSES
QUALITY ANALYSIS OF MICROSTRUCTURAL CONSTITUENTS OF AlMg9 ALLOY
A B
C D
Microstructure of the sample cast in croning cell, obtained on the scanning electron microscope (SEM) with the marked
places of quantitative analysis performing by EDS, magnification 200X.
αAl (matrix) - D Alx(Fe,Mn)ySiz (white phase) - B Mg2Si (black phase) - C Al8Mg5 (light grey phase) - A
RESULTS AND DISCCUSSION
METALLOGRAPHIC ANALYSIS OF AlMg9 ALLOY
3 K/s 7 K/s 55 K/s 150 K/s
Micrographs (METALOGRAPHIC ANALYSIS row) and electrolytic etched micrographs (METALOGRAPHIC ANALYSIS-GRAIN SIZE row) for the grain size determination sequence, magnification 200X, all in relation to cooling rate.
RESULTS AND DISCCUSSION
Grain size per surface area dependence from the cooling rate.
NA = -3.32 e(-rc / 4.53) – 3.60 e(-rc / 81.25) + 11.47 No.gr./mm2 R2=1
RESULTS AND DISCCUSSION
PHASE ANALYSIS OF AlMg9 ALLOY
Micrographs (SEM row) and by software analyzed corresponding micrographs (PHASE ANALYSIS row), magnification 200X, all in relation to cooling rate.
3 K/s 7 K/s 55 K/s 150 K/s
RESULTS AND DISCCUSSION
MICROSTRUCTURE DEVELOPMENT OF THE AlMg9 ALLOY
Sample phase ratio
0,00
2,00
4,00
6,00
8,00
10,00
12,00
3 7 55 150r c / K/s
f (X
, A
lMg
9)
/ a
rea
%
Alx(Fe,Mn)ySiz
Mg2Si
Al8Mg5
Surface area of particular phases
0,00
20,00
40,00
60,00
80,00
100,00
120,00
140,00
160,00
3 7 55 150r c / K/s
P
/ m
m2
Alx(Fe,Mn)ySiz
Mg2Si
Al8Mg5
Lenght of particular phases
0,00
1,00
2,00
3,00
4,00
5,00
6,00
3 7 55 150r c / K/s
l / m
m
Alx(Fe,Mn)ySiz
Mg2Si
Al8Mg5
RESULTS AND DISCCUSSION
Thermal and microstructure analysis enables calculation of mathematical models which reveals that increase of cooling rate induce:
Lowering of significant temperatures of phase transformations TL, TE1 and TS
Narrowing of solidification interval
Significant growth of NA (6 →11)
Fine and homogeneous distribution of microstructural constituents
Increase of Mg2Si phase ratio; Alx(Mn,Fe)ySiz and Al8Mg5 ratio stayed unchanged
Decrease of particles length to final ~2 μm.
On the base of particular established phases ratios, surface area and elongation dependence regard cooling rate it is possible to predict microstructure development
of the multicomponent technical AlMg9 alloy.
CONCLUSION
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