Macrosegregation during directional solidification of Pb-Sb alloys

Abstract

Macrosegregation of Sb was investigated during directional solidification of binary Pb-Sb alloys containing 2.2 and 5.8 wt% Sb over growth rates varying from 0.8 to 30 μm s-1. The cellular to dendritic transition was observed at a growth rate of 3.0 μm s-1 in Pb-2.2 Sb alloy in contrast to a growth rate of 1.5 μm s-1 in Pb-5.8 Sb alloy. The chemical analysis data revealed considerable macrosegregation of Sb along the longitudinal section of alloys. The degree of macrosegregation increased with a decrease in the growth rate. This behavior is discussed in light of thermo-solutal convection in the mushy zone as well as that in the melt ahead of the solid-liquid interface. © 2009 TIIM, India.