USING A THREE-PHASE MIXED COLUMNAR-EQUIAXED SOLIDIFICATION MODEL TO STUDY MACROSEGREGATION IN INGOT CASTINGS: PERSPECTIVES AND LIMITATIONS

摘要

A three-phase model for mixed columnar-equiaxed solidification was recently developed. The most critical features, necessary for modelling the macrosegregation, were considered: the progressive growth of the columnar dendrite trunks from the ingot surface, the nucleation and growth of the equiaxed crystals including the motion of the equiaxed crystals, the thermal and solutal buoyancy flow and its interactions with the growing crystals (equiaxed and columnar), the transport of solute due to melt convection and equiaxed sedimentation, and the columnar-to-equiaxed transition (CET). Application of the aforementioned model is mainly limited by two factors: one is the extreme computational expense; one is the lack of reliable parameters required by the model. In order to perform a calculation of industry ingot (up to hundreds of tons) on the basis of the current computer resources, a compromise is often made between the model capability and the computational feasibility, i.e. some necessary model simplifications have to be made. In this article the ongoing efforts to scale-up the current model for industry applications are reported on.