Nanocrystallization of metallic glasses

The paper summarizes briefly the current status of research in the field of nanocrystallization of metallic glasses especially highlighting the influence of glass composition and conditions of devitrification process on size, morphology and composition of crystallization products. Conventional crystallization creates a nanocrystalline structure only in glasses with particular compositions. Any metallic glass, decomposing in a primary crystallization process, can be converted into partially nano crystalline material using non-conventional methods of heat treatment, e.g. high-temperature or low-temperature nanocrystallization. Temperature of devitrification process influences sizes and compositions of crystallization products for any volume fraction of crystalline phase. The change of crystallites sizes can change their morphologies. The change of a crystallite composition usually affects the lattice parameter but also can result in a change of crystallographic structure of the same phase or in formation of another phase. Composition of primary crystallites is dependent on temperature as well as on time of devitrification process. The lower the annealing temperature and the shorter the annealing time (smaller crystallites) the more the crystallites composition differs from the equilibrium state. (C) 2001 Elsevier Science B.V. All rights reserved.