Strengthening and weakening in the processing of ultrafine-grained metals

Abstract

It is now well established that ultrafine-grained (UFG) metals, with average grain sizes below 1 μm, may be produced by applying severe plastic deformation to bulk metals using processing procedures such as equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). Generally, these procedures lead to a significant strengthening in the material but there are some examples where processing by ECAP or HPT produces a significant weakening. This report examines examples of both strengthening and weakening in the processing of UFG metals.