Stress-induced phase transformation and strain rate effect in polycrystalline Mo nanowires

Abstract

Using molecular dynamics and modified analytic embedded atom methods, the stress-induced phase transformation and strain rate effect on deformation characteristics of polycrystalline molybdenum nanowires are studied at room temperature under uniaxial tensile strain. The results show the tensile ductility of the nanowires increases with increasing strain rate. The surface rupture occurs at one position as the strain is bigger than 6% at a strain rate of 0.01% ps −1, but it does at multiple positions in the range of larger strain at higher strain rate. Moreover, an increased strain rate delays the appearance of “face-centered cubic (fcc)” atoms, but increases the peak fraction of “fcc” atoms. During the deformation process, two kinds of structure transformation are observed: (1) the “body-centered cubic (bcc)” configuration transforms into “other” configurations, and subsequently the “other” configurations transform into the “fcc” or “hexagonal close-packed (hcp)” configuration and (2) the “fcc” configuration converts into “other” configurations, and then into “bcc” or “hcp” configuration. In addition, the mechanical properties of the polycrystalline nanowires are compared with those of single-crystalline nanowires.