Entropic stabilization of nanoscale voids in materials under tension.

Abstract

While preexisting defects are known to act as nucleation sites for plastic deformation in shocked materials, the kinetics of the early stages of plastic yield are still poorly understood. We use atomistic simulation techniques to investigate the kinetics of plastic yield around small preexisting voids in copper single crystals under uniaxial tensile strain. We demonstrate that at finite temperatures, these voids are stabilized by strong entropic effects that confer them significant lifetimes even when the static mechanical instability limit is exceeded. By virtue of its entropic nature, this effect is shown to be proportionally stronger at higher temperatures. Even accounting for thermal activation, very small voids prove to be extremely inefficient nucleation sites for plasticity.