Compressive deformation of Fe nanopillar at high strain rate: Modalities of dislocation dynamics

Unlike the twinning-dominated tensile mode, compressive deformation of a bcc metallic nanostructure is known to be mediated by the glide of screw dislocations. Although the unusual attributes of bcc screw dislocations are well understood, it is still unclear how these unique effects are manifested in a nanoscale solid. In the present study, atomistic simulations render a close look at the dislocation activities underlying the compressive deformation of bcc-iron nanopillars at high strain rate. It is found that instead of performing simple glide motion, the line defects exhibit a host of complex features. In this regard, the temperature is observed to have a pronounced effect on the dislocation activities and consequently, on the overall plastic response of the material. Additionally, the simulations exhibit a direct correspondence between bursts in dislocation activities and jerky deformation of the pillar. This understanding is employed to gain an atomistic perspective of the statistical behavior of jerky yielding of these nanomaterials. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.