Solidification of ternary metal alloys .2. Predictions of convective phenomena and solidification behavior in Pb-Sb-Sn alloys

In Part I of this work, the continuum mixture model for binary alloys was extended to three component systems and used an idealized ternary phase diagram to provide the supplemental thermodynamic relations needed to close the model. In this paper, the new model is applied to the solidification of four lead-rich Pb-Sb-Sn alloys. System-specific information needed to close the model presented in Part I is extracted from the lead-antimony-tin phase diagram. Numerical simulations are performed to demonstrate similarities and differences between the macrosegregation patterns and convective flows of these ternary alloys and of two component systems. Macrosegregation of the solutes is altered significantly from the familiar patterns of the binary systems only when solidification in the doubly saturated binary troughs occurs near the liquidus interface. If the secondary and tertiary crystallization occur deep in the mushy zone, the resulting microsegregation has only small effects on the final redistribution of solute. (C) 1997 Elsevier Science Ltd.