Modeling macrosegregation during direct-chill casting of multicomponent aluminum alloys

A macro segregation model for direct chill casting of multicomponent aluminum alloys is implemented using the macroscopic transfer model, microsegregation model, and phase diagram calculation module, and applied to an Al-Cu-Mg alloy. The phase diagram calculation module is based on the TQ-Interface of CALPHAD software THERMO-CALC and the mapping technique initially proposed by Dore et al. This mapping technique is modified in arranging the mapping axes where the tabulation is performed to increase the access efficiency. This strategy provides a practical solution for quick access to phase diagram data in modeling macrosegregation of multicomponent alloys. It is found from our simulation that the contribution of each of the solute elements to the solutal buoyancy affects the final segregation pattern. The appropriate choice of the solidification path is important for the shrinkage-induced macro segregation. The model is applied to a real direct-chill (DC) casting experiment and a reasonable semiquantitative agreement with experimental data has been obtained, though the model does not take into account the possible contribution of floating grains and exudation.