multi-phase micro-segregation modelling during solidification of...

Prof. Dr. Ing. A. Bührig-Polaczek

Thermo-Calc Anwendertreffen, Aachen 2007

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


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


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


Specific Problems Modelling Ductile Iron

φG γ L

G

γL

- Morphology (graphite nodule in an austenite shell), mixed morphology: primary austenite and secondary eutectic cells

ΔT

Pop

ulat

ion

(m-3

)

N‘

ΔTN

ΔTσ

- Nucleation of stable and meta-stable phases- Cross-diffusion of C-Si-Cu in austenite

- Solid state transformations


MicroPhaseA Multi-Phase Micro-Segregation Model

Lα

β

Lxαx


Rough Flow Chart of MicroPhase

START Micro-Module

Temperature Criterion

Termination Criteria

END Micro-Module

Micro-SegregationObtaining Phase Fractions

Enthalpy of the SystemEnergy Conservation

No

Yes

No

Yes

Thermodynamic CalculationEquilibrium Concentrations

Solving Flux-BalancesNew Phase Fractions

Calculating DiffusionSolving Solutal Conservation Equations

Solving Flux-BalancesLiquid Concentrations due to Diffusion


Discretised Solutal Balance Equations Across Solid-Liquid Interfaces


Discretised Solutal Conservation Equationfor a Volume Element k


Typical ResultsPhase-Fractions, Temperature Curves

GJS-AX-NiCr 20 2Fe C3 Si2 Mn2 Ni20 Cr2 Cu0.5


Typical ResultsMaterial Properties (Cp, ρ, H, S, Lf, fs)



Comparing Liquid Fraction for an Equilibrium, A Gulliver-Scheil, and a Diffusion Controlled Approach



The Representative Volume Elementfor GJS-AX-NiCr 20 2


Process Simulation: Clamp-Ring


MAGMASOFT Using MicroPhase ResultsMaterial Specific Data


MAGMASOFT Using MicroPhase Results Density (T)


MAGMASOFT Using MicroPhase Results Specific Heat Capacity (T)


MAGMASOFT Using MicroPhase Results Solid Fraction (T)


MAGMASOFT Predicting Porosity UsingMicroPhase Data (Specific Heat Extraction Rate)


Solidification Result of MAGMASOFT UsingMicroPhase Data (Spec. Heat Extraction Rate)


Comparing Predicted t-T-CurvesMicroPhase, 1. MAGMA & 2. MAGMA Simulation


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


Principle of CouplingMAGMASOFT, MicroPhase, and Thermo-Calc

Makro-ProgrammMAGMASOFT©

Micro-ProgramMicroPhase

TD-DatenbankSchnittstelle

Main-Processing

h,μ Tx,

THΔΔ

tT Δ,

Post-ProcessingVerbesserte Temperaturrechnung

Charakteristische AbständePhasenanteile

Lunkerprognose

Pre-Processing


Simulated Geometry: ¼ CubeGJS-AX NiCr 20 2 (144 VE‘s in 2h), Green-Sand Mould

x

z


Un-Coupled Solution: Solidification Time


Coupled Solution: wt.-fraction graphite


Coupled Solution: wt.-fraction M7C3


Coupled Solution: wt.-fraction Austenite


Un-Coupled Solution: Porosity

multi-phase micro-segregation modelling during solidification of...

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