Strengthening Mechanism in Metals with Nano-scale Twins

Abstract

Methods used to strengthen metals typically also cause a pronounced decrease in ductility. Here we review a novel approach to realize significant strengthening while maintaining a reasonable ductility by nanoscale coherent twins. By introducing a high density of nano-scale twins in pure Cu, high strength and good ductility are achieved simultaneously. Particularly, a maximum strength was found in the nanotwinned Cu at a twin thickness of 15 nm, followed by a rapid softening and a monotonic enhancement in both the strain-hardening and ductility at smaller twin thicknesses. These unique properties and related dislocation–twin boundary strengthening mechanism differ fundamentally from the dislocation-grain boundary strengthening mechanism.