In situ mechanical crystallization of amorphous alloys

Abstract

Metallic glasses or amorphous solids are metastable and therefore they transform to the equilibrium stable phases on thermal annealing. In recent years it has been shown that deformation of metallic glasses also results in their crystallization, referred to as mechanical crystallization. Two different types of mechanical crystallization processes have been identified. One is the ex situ mechanical crystallization, a two-stage process, where a metallic glass, produced by any of the non-equilibrium processes, crystallizes on subjecting it to mechanical deformation. The other is in situ mechanical crystallization, a single-stage process, where a metallic glass or an amorphous solid produced by mechanical alloying crystallizes on continued milling for a longer period. This route seems to offer many advantages. The present article reviews the current literature – briefly on ex situ mechanical crystallization, and in detail on in situ mechanical crystallization – and presents the prospects of this interesting route of producing alloys containing either amorphous or crystalline, or different combinations of these two types.