Restriction or acceleration: Investigation on the remelting/resolidification process during Sn–Ni peritectic solidification in a temperature gradient

Abstract

In this work, extensive remelting/resolidification process induced by diffusion on the secondary dendrite arms in the mushy zone was confirmed in a Sn–Ni peritectic alloy. Examination on the dependence of λ2 on local solidification time showed that the remelting/resolidification process on secondary dendrite arm by the Gibbs-Thomson effect was restricted at the initial of peritectic reaction. Then, this restriction turns to disappear as directional solidification proceeds. Experimental observation shows that the remelting/resolidification on secondary dendrite arm could be attributed to both the Gibbs-Thomson and temperature gradient zone melting (TGZM) effect. Further analysis showed that this remelting/resolidification process was complicated in peritectic alloys due to interaction between peritectic reaction and the TGZM effect by the imposed temperature gradient. It was found that the influence of peritectic reaction on the remelting/resolidification process was different at different stages of solidification. The restriction or acceleration of the Gibbs-Thomson effect by peritectic reaction at different stages of solidification was clarified by diffusion-controlled analytical model describing the remelting/resolidification process. The dependence of the remelting/resolidification process on secondary dendrite arm on solidification time can be attributed to the interaction between peritectic reaction, the Gibbs-Thomson and TGZM effects.