Investigations on interfacial reactions at reentrant corners

Abstract

Interfacial reactions in Bi/Ni, Sn/Co, and Sn/Te systems that exhibit unique cruciform pattern formation are investigated. Different from the couples examined in the past, the solid substrates, Ni, Co, and Te, are placed outside the couples while constituents of low melting temperature, Bi and Sn, are placed in the center. With interfacial reactions proceeding in these couples, the reaction products grow inwardly at reentrant corners, and shrinking of the reaction layer at the corner is observed. As a result of the volumetric changes caused by interfacial reactions, stresses are built up in the couples, and stress-intensified locations are found at reentrant corners. The built-up stresses alter the diffusion rates and thus retard the reaction at the corners. Instead of forming cruciform patterns, the inner reactant is of flat shuriken shape after reactions.