Secondary dendrite arm migration caused by temperature gradient zone melting in the directionally solidified Sn–40 at.% Mn peritectic alloy

Abstract

Sn-40 at.% Mn peritectic alloys were directionally solidified at different growth rates (1-100 lm/s) under a steep temperature gradient (40 K/mm). The migration of secondary dendrite arm was observed in this peritectic alloy in which both the primary phase and the peritectic phase are intermetallic compounds with nil solubility. This migration is caused by coupling remelting/solidification at the hot/cold sides of the liquid pool between two adjacent secondary dendrite arms by temperature gradient zone melting. Its novel feature is that the remelting temperature of primary phase is a little higher than the solidification temperature of peritectic phase. Analytical solutions based on the assumption that the solubility of both primary and peritectic phases are nil have been proposed to describe this migration. It has also been found that the migration of secondary dendrite arm is most obvious at intermediate growth rates under steep temperature gradient in the directionally solidified Sn-40 at.% Mn peritectic alloy.