The diffusion-controlled remelting/resolidification process in directionally solidified Sn-Mn peritectic alloy

Abstract

The Sn-40at.%Mn peritectic alloy were directionally solidified in a temperature gradient at different growth velocities. It was demonstrated that the diffusion-controlled remelting/resolidification process occurred on the secondary dendrite arms in the mushy zone of Sn-40at.%Mn peritectic alloy. Theoretical analysis has shown that the diffusion-controlled solute transport which occurred between secondary dendrite arms was produced by both the temperature gradient zone melting (TGZM) and the Gibbs-Thomson effects (capillary effect). An analytical model was established to describe the diffusion-controlled solute transport during the remelting/resolidification process. The coupling influences of the TGZM and Gibbs-Thomson effects on the remelting/resolidification process during peritectic solidification was analyzed in terms of the specific surface area (SV) of dendrites. It was found that the remelting/resolidification process by the Gibbs-Thomson effect was retarded by peritectic reaction, while that by the TGZM effect was accelerated by peritectic reaction. Since the diffusion-controlled solute transport by the TGZM effect is dominant as compared with that by the Gibbs-Thomson effect in this work, the diffusion-controlled remelting/resolidification process of dendrites is accelerated during peritectic solidification in a temperature gradient.