Thermodynamic Calculations in Mg-alloy Systems

Transcription

1 Karlsruher Institut für echnology (KI) Institut für Angewandte Materialien Angewandte Werkstoffphysik hermodynamic Calculations in -alloy Systems Hans J. Seifert Nadine Heiden, Damian Cupid hermo-calc Anwendertreffen, September 211

2 Institut für Angewandte Materialien Angewandte Werkstoffphysik hermodynamic Calculations in -alloy Systems - Introduction - Calphad - Cast rolling and hot rolling - Phase modeling and calculations - Solidification, microstructure development hermo-calc Anwendertreffen, September 211

3 Equilibrium Calculations Optimization Computational hermodynamics heory Quantum Mechanics, Statistical hermodynamics Estimates Experiments DA, Calorimetry, EMF, Knudsen Effusion, Metallography, X-ray Diffractometry,... CALPHAD Models with adjustable Parameters CALculation of PHAse Diagrams Ab-initio Calculation Adjustment of Parameters hermodyn. Functions, H, S, C p Storage in Databases Equilibria Phase Diagrams raphical Representation Application Kinetics

4 Computational hermodynamics, Integration of Methods Molecular dynamics Ab-initio calculations Experiments hermodynamic data, Phase diagrams Data for interface energies, lattice parameters, elastic constants Kinetic data Reactor simulation CALPHAD Scheil solidifiaction hermodynamic databases Databases for interfacial energies, lattice parameters, elastic constants Kinetic databases Phase field methods Physical data of materials Sharp Interface Microstructure development

5 ICME Integrated Computational Materials Engineering, ICME, is the integration of materials information, captured in computational tools, with engineering product performance analysis and manufacturing-process simulation Pollock M, lison JE, Backman D, Boyce MC, ersh M, Holm EA, LeSar R, Long M, Powell IV AC, Schirra JJ, Demania Whitis D, Woodward C, Integrated Computational Materials Engineering A ransformational Discipline for Improved Competitiveness and National Security, Washington, DC he National Academies Press, 28. <http//

6 Magnesium alloys in light construction Density of Magnesium, ρ = 1,74 g/cm 3 75% lighter than steel 35% lighter than uminum Hexagonal close packed crystal structure < 225 C Base gliding twins > 225 C new glide systems Forming difficult and expensive Door inner reinforcement Melting point 65 C 4% Schwindung during solidification Roof inner reinforcement

7 F Magnesium Flachprodukte, Freiberg (Sachsen) Cast rolling + hot rolling Door inner reinforcement 53 Ingots Coils Endabmessungsnahe Fertigung 97 e.g. AZ31-Legierung, 2,5-3,%,,6-1,%Zn + other elements according to ASM B9/B9M-93 Roof inner reinforcement

8 F Magnesium Flachprodukte, Freiberg (Sachsen) Cast rolling + hot rolling Roughed strip Strip > 55 C - AZ alloy 4 C

9 --Zn-Cu System Commercial loys -loys AZ-Series e.g. AZ91 -loys 7XXX-Series e.g. AA775-6 Zn Experimental Investigations hermodynamic Simulations

10 --Zn System 34 ernary loys Induction melting of initial mixtures (raphite-crucible in water-cooled Cu-crucible, He-atmospheres); Heat treatment at 335 C and 4 C, 19 days ICP-AES, REM /EDX, XRD, DA, DSC, EPMA Zn

11 . EPMA + (), 19d f + (), 19d + f+

12 Compound Energy Formalism Surface of Reference (A,B) k (D,E) l Solution Phase with wo Sublattices (S) and 4 Species (J)

13 Modeling of the -Phase in the --Zn(-Cu) System 32 (,Zn) 49, Pearson Symbol CI162, Space roup Im3 () 26 (,) 6 (,Zn,) 48 () 1 ibbs Free Energy of the Solution Phase Ideal mix Excess mix

14 Compound Energy Formalism Surface of Reference () 26 (,) 6 (,Zn,) 48 () 1 6 formal compounds Zn Zn Zn Zn fcc fcc fcc 7 fcc fcc 8 fcc hcp hcp hcp hcp 48 hcp hcp 48 hcp Zn hcp Zn

15 Compound Energy Formalism Surface of Reference () 26 (,) 6 (,Zn,) 48 () 1 6 formal compounds Zn Zn Zn Zn59.26

16 Compound Energy Formalism Surface of Reference () 26 (,) 6 (,Zn,) 48 () 1 6 Compounds Zn Zn o be adjusted precisely o be adjusted precisely Describes -rich limit of Describes -poor limit of Describes -poor limit of Not significant. Antistructure atoms on sublattices 2 and 3.

17 Compound Energy Formalism Surface of Reference () 26 (,) 6 (,Zn,) 48 () 1 Interaction parameters L, Zn L, L, L, Zn L, Zn L, Zn

18 hcp fcc hcp Zn hcp fcc Zn hcp fcc hcp fcc hcp Zn hcp fcc Zn hcp fcc Zn Zn Zn Zn L L L L L L,,,,,, ibbs Free Energy of -Phase () 26 (,) 6 (,Zn,) 48 () 1

19 Extrapolation - emperature - Composition Section at 2at% Zn Mol%

20 loys in the --Zn System Extrapolations in comparison with experimental data emperature-concentration sections Zn 1, 2, 3 mass% Zn 4, 5, 6 mass% Zn 7, 8, 9 mass% 2

21 emperature-concentration Sections 2, 43 mol% Zn Zn Zn 2 36 mol%

22 Partial and integral enthalpies of Zn in ternary liquid phase, 66 C =13 =31

23 Partial and integral enthalpies of in ternary liquid phase, 61 C 61 C Zn=32 61 C

24 - - Zn System Isothermal section at 35 C

25 - - Zn System Isothermal section at 25 C

26 - - Zn System Projection of solvus surface for ()-rich side Partial isothermal section at 25 C

27 - - Zn System Dataset for --Zn refined -Zn Phase diagram according to P. Liang (1998) separate thermodynamic description of pure (stable) phases and Zn Implemented in the dataset by R. Schmid-Fetzer, J. röbner (21) uniform description of both hcp phases

28 Solidification of AZ91 -loy ()-Solvus und Solidus im --Zn System

29 Equilibrium Solidification of AZ91 -loy Equilibrium Solidification 456 C

30 Scheil Solidification C f k kc (1 f ) s s s 1 f f L 1 1 k 1 Local equilibrium at the solid / liquid interface Rapid diffusion of the elements in the liquid phase No diffusion in the solid phase C s C f s L f k Composition of the solid phase Composition of the alloy Fraction of the solid phase Liquidus temperature Solidus temperature Partition coefficient

31 Solidification of AZ91 -alloy Solidification 456 C () Δ 118 C Solidification 338 C () γ ()

32 Scheil solidification of AZ91 -alloy Heat evolution AZ91 alloy microstructure after casting () Liquid, () () () Liquid, (), γ γ

33 Scheil solidification of AZ91 -alloy Weight fraction of elements, (ss) Weight fraction of elements, liquid phase

34 Coupling with phase field method Calculated primary crystallization fields for the ternary system --Zn (dashed line) and the quaternary --Mn-Zn-system with 1% wt. Zn (dashed lines). Symbol Composition of the AZ31 alloy. roup of Prof. Rainer Schmid-Fetzer, U Clausthal B. Böttger, J. Eiken, M. Ohno,. Klaus, M. Fehlbier, R. Schmid-Fetzer, I. Steinbach, A. Bührig-Polaczek, Adv. Engin. Mater. 8 (26)

35 Coupling with phase field method Directional growth of AZ31 in experiment and qualitative comparison to simulation. B. Böttger, J. Eiken, I. Steinbach, Acta Materialia 54 (26)

36 Coupling with phase field method AZ31 reference alloy composition raised from 3 to 6 wt.% Seed density function raised by factor 5 Heat extraction rate increased from 25 to 1 J/cm -1 s -1 Simulated solidification microstructures for AZ31 alloy B. Böttger, J. Eiken, I. Steinbach, Acta Materialia 54 (26)

37 High Strength loy AA775-6 Component Mass% Cu Zn Cr Fe max..5 Mn max..3 Si max..4 Other, each max..5 Other, total max..15

38 loys, Series 7 in the -Cu--Zn System Zn Cu 38

39 -Cu--Zn System - 673K, 4 at.% section indicated Zn Cu

40

41 Conclusions - hermodynamic simulations describe multi-component systems in a reasonable way - Confirmation of calculations from experimental results - High-temperature stabilities, -compatibilities and reactions - Coupling with Phase Field Methods is possible hermodynamic modeling, Computer simulations + Experiments, analyses, tests Efficient materials analysis and materials development

42 Acknowledgements

43 loy AA775 Element solubility in uminium Phase fraction diagram Calculation with JMatPro 43

44 loy AA775 Metastable phase formation η, S,, P Calculation with JMatPro f f -Diagram exp N t ransition fraction, rowth rate, t 3 N ime Nucleation rate, Johnson-Mehl-Avrami Equation

45

46 -Cu--Zn System, 673K Zn Cu

47 -Cu--Zn System - 673K, 33.3 at.% section indicated Zn Cu

48 Cu

49 -Cu--Zn System - 673K, Cu = 65 section indicated Zn Cu

50 Cu