A model of micro-pillar plasticity controlled by the nucleation of dislocations at free surfaces was developed using methods of dislocation dynamics innovated by Johnston and Gilman 50 years ago. It was shown that the stress dependence of the rate of nucleation could be related to the dependence of the flow strength upon the diameter of the pillar. The steady state flow stress in this model depended only upon the kinetics of nucleation, whereas the transient deformation behaviour depended upon the initial dislocation density and the dislocation mobility, as well as the rate of nucleation. The model could describe not only the dependence of the strength upon pillar diameter, but also recent experiments on face-centered cubic gold crystals, wherein pre-straining led to softening and annealing led to hardening. The model did not account for the stochastic, jerky nature of plastic flow in micro-pillars and was not meant to apply to pillars large enough to support substructure formation.

Micro-Pillar Plasticity Controlled by Dislocation Nucleation at Surfaces. W.D.Nix, S.W.Lee: Philosophical Magazine, 2011, 91[7-9], 1084-96