Temperature and Strain-Rate Dependence of Surface Dislocation Nucleation

TLDR

Dislocation nucleation is essential to plastic deformation in small-volume crystalline solids, and free surfaces can act as effective dislocation sources to initiate and sustain plastic flow. The study aims to develop an atomistic modeling framework to investigate the probabilistic nature of surface dislocation nucleation. The framework employs atomistic simulations to model surface dislocation nucleation. The activation volume for surface dislocation nucleation is 1–10 b³, making the nucleation stress highly sensitive to temperature and strain rate and setting an upper bound on the size–strength relation in nanopillar compression.

Abstract

Dislocation nucleation is essential to the plastic deformation of small-volume crystalline solids. The free surface may act as an effective source of dislocations to initiate and sustain plastic flow, in conjunction with bulk sources. Here, we develop an atomistic modeling framework to address the probabilistic nature of surface dislocation nucleation. We show the activation volume associated with surface dislocation nucleation is characteristically in the range of 1-10b3, where b is the Burgers vector. Such small activation volume leads to sensitive temperature and strain-rate dependence of the nucleation stress, providing an upper bound to the size-strength relation in nanopillar compression experiments.