New procedure to generate stable nanocrystallites by severe plastic deformation

A new method to produce bulk nanocrystalline metal matrix composites is presented. A metal powder is treated to obtain a relatively brittle layer with a defined thickness on the surface. The precompacted powder is deformed by high-pressure torsion until a dense bulk nanocrystalline material is formed. Due to fragmentation of the thin layer, it is possible to incorporate nanometre-sized dispersions into the nanocrystalline metal matrix. As an example, an oxidized nickel powder is investigated in which the thermal stability and microhardness are extraordinarily enhanced.