Analysis of Peritectic Solidification of Ag–Sn Alloys by Unidirectional Solidification Experiment

Abstract

In the peritectic solidification, the same solute has been ejected toward the liquid during the growth of primary and secondary phases and these two phases grow interacting with each other. In this study, the unidirectional solidification experiments by using binary Ag–Sn alloy have been performed to find the layered structure solidification, in which primary phase and secondary phase alternately grow in hyper-peritectic Ag–Sn alloy. In order to clarify the mechanism of the aforementioned solidification phenomena, the relationship between fractional solid and Sn concentration distribution obtained by FE-EPMA was examined by using the random sampling methods. Through some theoretical analysis, it has been estimated that solute convection due to the density difference between bulk and inter dendritic liquid could occur and the growth and decline of primary phase could be repeated periodically in the unidirectional solidification. Based on these results, a mechanism for the occurrence of the layered structure solidification induced by solute convection was proposed. Furthermore, it was confirmed that the layered structure solidification also occurs in hypo-peritectic under conditions that promote convection, revealing that the presence or absence of convection directly influences the occurrence of the layered structure solidification.