SOLIDIFICATION OF A BINARY ALLOY FROM A COLD WIRE OR PIPE: MODELING OF THE MIXED-PHASE REGION

Abstract

This paper presents a theoretical study of the heat and mass transfer phenomena occurring during the solidification of a binary alloy from a thin cold wire or pipe modeled as a line heat sink. The study accounts for the existence of a mixed-phase region (mushy zone) separating the solid from the liquid regions. The mushy zone consists of a complex mixture of liquid and dendrites, whose composition depends on both position and time and cannot be prescribed a priori. The growth rate of the mushy zone (which has a paramount effect on the structure of the resulting solid) depends on the heat and mass transport processes that govern the solidification phenomenon. The results of this study illuminate the dependence of the temperature, concentration, and liquid fraction distributions in the mushy zone on several dimensionless groups of the problem. The study also found that the growth rate or even the very existence of the mixed-phase region is controlled by the values of these dimensionless groups.