Analysis of size-dependent slip transfer and inter-twin flow stress in a nanotwinned fcc metal

Abstract

Nanotwinned structures offer the potential to effectively enhance strength while preserving ductility and damage tolerance. In this paper we present an analytical model for quantifying slip transfer across twin boundaries and for deriving the attendant flow stress as a function of the twin lamellae size in nanotwinned face-centered cubic metals. The mechanistic models investigate how single or piled-up screw and non-screw dislocations interact with twin boundaries, by establishing connections with the size dependence of the activation volume. The models correctly predict the trends from a variety of independent prior experimental observations of the dependence of flow stress on twin lamella size in nanotwinned copper. They also rationalize a number of observations made from previous molecular dynamics simulations of the deformation of nanotwinned metals.