NUMERICAL-SIMULATION OF MACROSEGREGATION - A COMPARISON BETWEEN FINITE-VOLUME METHOD AND FINITE-ELEMENT METHOD PREDICTIONS AND A CONFRONTATION WITH EXPERIMENTS

Micro-macrosegregation calculations have been performed for a rectangu lar cavity containing either a Pb-48 wt pct Sn alloy or a Sn-5 wt pct Pb alloy. The numerical results calculated with a finite volume method (FVM) and a finite element method (FEM) are compared with experimenta l results previously obtained by Hebditch and Hunt.([1]) The two metho ds are based on the same average conservation equations governing heat and mass transfer and the same assumptions: lever rule, equal and con stant density of the solid and liquid phases (except in the buoyancy t erm), permeability of the mushy zone given by the Carman-Kozeny relati on, and no transport of the solid phase. Although the same parameters are used in both calculations, small differences are observed as a res ult of the different formulations. In particular, the instabilities ap pearing in the mushy zone (channels) of the Sn-5 wt pct Pb alloy are m ore pronounced with the FVM formulation as compared with FEM, whereas the opposite trend is observed for the Pb-48 wt pct Sn alloy. Neverthe less, the final segregation maps at the end of solidification compare fairly well with the experimental findings.