Atomistic views of deformation

Abstract

Fully dynamic atomistic simulations of plastic deformation in metals are so computationally demanding that materials physicists have instead developed mesoscale proxies to model dislocation dynamics. In this paper, Vasily Bulatov and colleagues take on the challenge of modelling metal plasticity at the atomic level. Such simulations require models that contain many millions of atoms (the largest simulation in this study contains 268 million atoms), and algorithms are used to process the datasets down to a volume that allows human interpretation. The authors probe ultrahigh-strain-rate deformation in body-centred-cubic tantalum, a model metal, to investigate the limits of metal plasticity. They show that at certain limiting conditions, dislocations can no longer relieve metal loading and twinning takes over. At a strain rate lower than this limit, flow stress and dislocation density achieve a steady state and a sort of metal kneading is observed. The simulations support previous proposals of the maximum dislocation density that can be reached before a metal collapses.