A new strain-rate-induced deformation mechanism of Cu nanowire: Transition from dislocation nucleation to phase transformation

The plastic deformation mechanism of Cu nanowires is studied using the molecular dynamics simulation method by applying uniaxial tension along the [1 0 0] direction at a constant strain rate and constant temperature. At high strain rate and low temperature, we find a new face-centered cubic-body-centered cubic-hexagonal close-packed (fcc-bcc-hcp) phase transformation mechanism, which controls the plastic deformation of the Cu nanowire. If we raise the nanowire's temperature at a high strain rate, the plastic deformation mechanism will transform from the fcc-bcc-hcp phase transformation mechanism to the well-known momentum-induced-melting mechanism. On the other hand, if we reduce the applied strain rate to a certain level, the plastic deformation mechanism will transform into a dislocation nucleation mechanism. Based on the present study we have proposed a strain rate-temperature plastic deformation map for Cu nanowires. This map tells a vivid story about the transition among the three different plastic deformation mechanisms, and will help us develop a deep understanding of the plastic deformation of Cu nanowires.