NUCLEATION ISSUES IN SOLID-STATE AMORPHIZATION

There are two important nucleation problems in solid state amorphization. One is to understand how an amorphous phase forms at an interface between two crystalline elements; the other is to explain how nucleation of a crystalline compound at an advancing interface between an amorphous alloy and a crystalline element is suppressed until the amorphous layer has attained a temperature- and system-dependent critical thickness. This article discusses both issues. It also examines the relationship between transient nucleation and competitive growth models for phase suppression in thin-film diffusion couples. A transient-nucleation model is used to represent information about the transition from growing amorphous alloy to growing a crystalline intermetallic on two kinds of map: one of layer thickness against temperature, the other of temperature against anneal time. The discussion concentrates upon the most-studied amorphizing system, Ni-Zr, though the points made may be relevant in interpreting solid state amorphization in other systems. © 1990 Taylor & Francis Ltd.