Solidification of a ternary metal alloy: A comparison of experimental measurements and model predictions in a Pb-Sb-Sn system

Experiments were performed with a Pb-5 pct Sb-35 pct Sn system to experimentally validate simulations made with a continuum mixture model for ternary alloy solidification. Temperature histories were measured during casting, and composition profiles were found in the solidified ingot. Dendritic arm spacings were found from optical micrographs of the alloy microstructure and used to determine a constant in the Blake-Kozeny submodel for the mushy zone permeability in the liquid-solid interaction term of the momentum equations. Scaling analysis from a previous work and a large uncertainty in the permeability constant suggested that predictions of the composition are extremely sensitive to the choice of a permeability model. Three simulations were performed using the permeability constant as a parameter, and measured temperatures and compositions were compared with predictions based on different model constants. While the thermal histories had good agreement, the results near the liquidus interface, where all of the significant advection of solute occurs, suggest that the Blake-Kozeny model significantly underpredicts the resistance of the dendritic array to fluid flow.