Nucleation issues in solid state amorphization

Abstract 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.