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Pseudo-front tracking model for the description of primary and secondary phases formation during solidification of multicomponent alloys

A numerical model based on a pseudo-front tracking method has been developed in order to describe the formation of the microstructure during solidification of multicomponent systems. This two-dimensional model can simulate the growth of individual dendritic or globulo-dendritic grains in a selected zone of a casting. The model provides a direct simulation of the grain morphology evolution and microsegregation patterns. The method is based on the resolution of the solute diffusion equations including the effect of interface curvature. The calculations are performed from the knowledge of the average local concentrations at the end of solidification and of the local thermal history. These quantities are obtained by measurement or from a macroscopic calculation on the scale of the casting.

The pseudo-front tracking model has been extended to describe the formation of the secondary phases in the interdendritic regions, after the temperature for eutectic or peritectic phases has been reached. Considering the effect of back-diffusion and cooling, the model can predict the type, the amount and the spatial distribution of the secondary phases.

The model is coupled to the phase diagram software Thermo-Calc, allowing therefore applications to complex alloys.

During the project the model is validated against experimental data for 3xxx and 5xxx series alloys. This comprehensive microstructure model can be used to perform predictive simulations of as-cast microstructures as a function of alloy composition and cooling conditions. Comparisons with 3xxx and 5xxx series alloys are presently underway.

Reported by

Ecole Polytechnique Fédérale de Lausanne
Laboratoire de métallurgie physique
1015 Lausanne
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