Influence of solutal convection on solute distribution of melt during preparation of directionally solidified Sn–36 at.%Ni peritectic alloy

Abstract

Experiments consisting of melting followed by thermal stabilization on Sn–36at.%Ni peritectic alloy have been carried out in a Bridgman-type furnace. Due to imposed temperature gradient, a mushy zone is created between the complete liquid zone and the non-molten zone. Microstructure evolution and solute distribution in the melt during thermal stabilization have been characterized. As thermal stabilization time increases, the volume fraction of liquid in the mushy zone decreases. A Sn boundary layer which results from evacuation of liquid in the mushy zone is built up at the solid/liquid interface at the initial of thermal stabilization then gradually disappears. A model is proposed to describe this boundary layer which is influenced by solutal convection during thermal stabilization. It is found that solute segregation in the complete liquid zone can be destroyed by solutal convection. This solute boundary layer can lead to further downward migration of the solid/liquid interface during thermal stabilization.