INVESTIGATION OF MICROSTRUCTURE FEATURES OF AlMg9 ALLOY

Transcription

1 INVESTIGATION OF MICROSTRUCTURE FEATURES OF AlMg9 ALLOY Zdenka Zovko Brodarac, Jožef Medved 2, Primož Mrvar 2 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

2 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

3 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

4 INTRODUCTION Al-Mg SYSTEM Al-Mg-Si SYSTEM Solid phase distribution in aluminum reach corner of the Al Mg Si diagram. Aluminum corner of the Al Mg phase diagram Invariant reactions in ternary alloys of the Al-Mg-Si system Compositions of liquid Reaction T / C Mg / mass. % Si /mass.% L α Al + Mg 2 Si (quasibinary section) 595 8,15 7,75 L α Al + (Si) + Mg 2 Si 555 4,96 12,95 L α Al + Mg 2 Si + Al 8 Mg ,2 0,37

5 INTRODUCTION THE AIM OF THIS INVESTIGATION: 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 (N A ) of the corresponding microstructure related to the cooling rates.

6 EXPERIMENTAL CHEMICAL ANALYSIS: charge material - ingots of the quality EN (AlMg9) alloy chemical composition - spectrometer Spectro DIN 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. 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.

7 EXPERIMENTAL 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 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 EDS

8 EXPERIMENTAL SAMPLE FROM THE CRONNING CELL 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; x - X series of the microphotographs recording; (100x) SAMPLE FROM THE CONIC MOULD

9 RESULTS AND DISCCUSSION 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 1,212 0,757 0,0543 0, ,08 0,0034 0,0086 0,0231 0,0904 AlMg9 w mass.% 8,0 - EN AC-AlMg9 2,5 1,0 0,10 0,55 0,25 0,20 10,5

10 RESULTS AND DISCCUSSION THERMODYNAMICAL MODELING OF THE PHASE DIAGRAM OF AN AlMg9 ALLOY BY THE ThermoCalc (TCW 5.0) SOFTWARE -initial condition: T = 743 C, p = 10 5 MPa, default chemical composition PHASES EVALUATION: Al 13 Fe 4 Al 6 Mn α Al Mg 2 Si AlMg-β Thermodynamical calculation of the equilibrium phase diagram of examined AlMg9 alloy. Polytherm section of the equilibrium phase diagram. T L 658,25 3,54 % Si 5 % Cu 2,29 % Fe 1,90 % Mn 5 % Mg 2,25 % Zn = 597,3 C T 410,09 140,17 % Si 3 % Cu 0,57 % Fe 7,96 % Mn 2,23 % Mg 10,76 % Zn = 559,5 C E, Mg Si 2

11 RESULTS AND DISCCUSSION RESULTS OF SIMPLE AND SIMULTANEOUS THERMAL ANALYSES Dependence of the significant temperature of phase transformations from the cooling rate of the AlMg9 alloy.

12 RESULTS AND DISCCUSSION QUALITY ANALYSIS OF MICROSTRUCTURAL CONSTITUENTS OF AlMg9 ALLOY A B 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. C α Al (matrix) - D Al x (Fe,Mn) y Si z (white phase) - B Mg 2 Si (black phase) - C Al 8 Mg 5 (light grey phase) - A D

13 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.

14 RESULTS AND DISCCUSSION Grain size per surface area dependence from the cooling rate. N A = e (-rc / 4.53) 3.60 e (-rc / ) No.gr./mm 2 R 2 =1

15 RESULTS AND DISCCUSSION PHASE ANALYSIS OF AlMg9 ALLOY 3 K/s 7 K/s 55 K/s 150 K/s Micrographs (SEM row) and by software analyzed corresponding micrographs (PHASE ANALYSIS row), magnification 200X, all in relation to cooling rate.

16 RESULTS AND DISCCUSSION MICROSTRUCTURE DEVELOPMENT OF THE AlMg9 ALLOY 160,00 140,00 120,00 100,00 Alx(Fe,Mn)ySiz Mg2Si Al8Mg5 12,00 P / mm 2 80,00 60,00 f (X, AlMg9) / area % 10,00 8,00 6,00 4,00 Alx(Fe,Mn)ySiz Mg2Si Al8Mg5 40,00 20,00 0,00 6, r c / K/s Surface area of particular phases Alx(Fe,Mn)ySiz Mg2Si Al8Mg5 2,00 5,00 4,00 0, r c / K/s Sample phase ratio l / mm 3,00 2,00 1,00 0, r c / K/s Lenght of particular phases

17 CONCLUSION Thermal and microstructure analysis enables calculation of mathematical models which reveals that increase of cooling rate induce: Lowering of significant temperatures of phase transformations T L, T E1 and T S Narrowing of solidification interval Significant growth of N A (6 11) Fine and homogeneous distribution of microstructural constituents Increase of Mg 2 Si phase ratio; Al x (Mn,Fe) y Si z and Al 8 Mg 5 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.

18 THANK YOU FOR YOUR ATTENTION!!!