Stochastic size-dependent slip-twinning competition in hexagonal close packed single crystals

Abstract

In this paper, we present an analytical model to investigate stochastic size effects on the critical stress for the activation of non-basal slip and contraction twinning (CT) in miniaturized hexagonal-close packed (HCP) single crystals. The analysis is based on the basic model developed by Parthasarathy et al (Scr. Mater. 56 313–6), but extends it to account for the mechanism-based description of pyramidal slip and CT in HCP metals. The results demonstrate that for a given initial dislocation density, a probabilistic competition exists among CT nucleation, CT growth and pyramidal slip. Based on the stochastic model, we construct a mechanism map that provides regimes of dominant deformation modes that govern the macroscopic yield stress in HCP single crystals.