Synthesis of nanostructured materials by mechanical milling: Problems and opportunities

Mechanical attrition as a method to produce nanocrystalline (nc) materials is reviewed. its advantages include the fact that all classes of materials-including brittle compounds-are amenable to the method; it can be easily scaled up to tonnage quantities. The phenomenology and suggested mechanisms for formation of nc microstructures are discussed for ball milling of single component powders, mechanical alloying of multicomponent powders, and mechanical crystallization of amorphous alloys. The phenomenology is well documented but microscopic mechanisms await better understanding of the nature of deformation processes in nc materials. The problems of contamination and powder consolidation are briefly considered. (C) 1997 Acta Metallurgica Inc.