Multi-Phase Micro-Segregation Modelling during Solidification of Ductile Iron

Transcription

1 Multi-Phase Micro-Segregation Modelling during Solidification of Ductile Iron B. Pustal, R. Berger, E. Subasic, G. Laschet, W. Schäfer, C. Bartels, A. Bührig-Polaczek Prof. Dr. Ing. A. Bührig-Polaczek

2 Outline About the Project Specific Problems Modelling Ductile Iron Introduction to MicroPhase Governing Equations Typical MicroPhase Results Results for GJS-AX-NiCr 20 2 Process Simulation Using MicroPhase Results Outlook First Coupled Results

3 Project of the DFG Transfer Domain Modelling Tools Relevant for Practice Sub-Project: A Thermodynamic-Kinetic Micro-Segregation Model - A comprehensive simulation tool for process and material dependent micro-structure simulations is to be developed by the cooperation of the four partners - Prediction of solidification paths of highly alloyed ductile cast irons - to predict feeding due to graphite precipitation and - for alloy, casting, and process development - For research and application of users in practice Clamp-ring made of EN-GJS SiMo 5.1 and EN-GJS-AX-NiCr 20 2

4 Population (m -3 ) Specific Problems Modelling Ductile Iron - Morphology (graphite nodule in an austenite shell), mixed morphology: primary austenite and secondary eutectic cells - Nucleation of stable and meta-stable phases - Cross-diffusion of C-Si-Cu in austenite - Solid state transformations N G γ L ΔT σ φ G γ L ΔT N ΔT

5 MicroPhase A Multi-Phase Micro-Segregation Model α L α x β L x

6 Rough Flow Chart of MicroPhase START Micro-Module Temperature Criterion Yes Micro-Segregation Obtaining Phase Fractions No Thermodynamic Calculation Equilibrium Concentrations Solving Flux-Balances New Phase Fractions No Termination Criteria Yes Enthalpy of the System Energy Conservation Calculating Diffusion Solving Solutal Conservation Equations Solving Flux-Balances Liquid Concentrations due to Diffusion END Micro-Module

7 Discretised Solutal Balance Equations Across Solid-Liquid Interfaces

8 Discretised Solutal Conservation Equation for a Volume Element k

9 Typical Results Phase-Fractions, Temperature Curves GJS-AX-NiCr 20 2 Fe C3 Si2 Mn2 Ni20 Cr2 Cu0.5

10 Typical Results Material Properties (C p, ρ, H, S, L f, f s ) GJS-AX-NiCr 20 2 Fe C3 Si2 Mn2 Ni20 Cr2 Cu0.5

11 Comparing Liquid Fraction for an Equilibrium, A Gulliver-Scheil, and a Diffusion Controlled Approach GJS-AX-NiCr 20 2 Fe C3 Si2 Mn2 Ni20 Cr2 Cu0.5

12 The Representative Volume Element for GJS-AX-NiCr 20 2

13 The Representative Volume Element for GJS-AX-NiCr 20 2

14 Process Simulation: Clamp-Ring

15 MAGMASOFT Using MicroPhase Results Material Specific Data

16 MAGMASOFT Using MicroPhase Results Density (T)

17 MAGMASOFT Using MicroPhase Results Specific Heat Capacity (T)

18 MAGMASOFT Using MicroPhase Results Solid Fraction (T)

19 MAGMASOFT Predicting Porosity Using MicroPhase Data (Specific Heat Extraction Rate)

20 Solidification Result of MAGMASOFT Using MicroPhase Data (Spec. Heat Extraction Rate)

21 Comparing Predicted t-t-curves MicroPhase, 1. MAGMA & 2. MAGMA Simulation

22 Future Work C cross-diffusion through austenite shell Implementation of a statistical nucleation model Direct coupling to MAGMASOFT Implementation of interface kinetics (short range diffusion) Prediction of solid state transformations

23 Principle of Coupling MAGMASOFT, MicroPhase, and Thermo-Calc Pre-Processing Main-Processing μ,h Makro-Programm MAGMASOFT T, Δt Micro-Program MicroPhase x, T TD-Datenbank Schnittstelle ΔH ΔT Post-Processing Verbesserte Temperaturrechnung Charakteristische Abstände Phasenanteile Lunkerprognose

24 Simulated Geometry: ¼ Cube GJS-AX NiCr 20 2 (144 VE s in 2h), Green-Sand Mould z x

25 Un-Coupled Solution: Solidification Time

26 Coupled Solution: wt.-fraction graphite

27 Coupled Solution: wt.-fraction M7C3

28 Coupled Solution: wt.-fraction Austenite

29 Un-Coupled Solution: Porosity