Molecular dynamics study of the mechanical behavior of nickel nanowire: Strain rate effects

We present the analysis of uniaxial deformation of nickel nanowires using molecular dynamics simulations, and address the strain rate effects on mechanical responses and deformation behavior. The applied strain rate is ranging from 1 × 108 s−1 to 1.4 × 1011 s−1. The results show that two critical strain rates, i.e., 5 × 109 s−1 and 8 × 1010 s−1, are observed to play a pivotal role in switching between plastic deformation modes. At strain rate below 5 × 109 s−1, Ni nanowire maintains its crystalline structure with neck occurring at the end of loading, and the plastic deformation is characterized by {1 1 1} slippages associated with Shockley partial dislocations and rearrangements of atoms close to necking region. At strain rate above 8 × 1010 s−1, Ni nanowire transforms from a fcc crystal into a completely amorphous state once beyond the yield point, and hereafter it deforms uniformly without obvious necking until the end of simulation. For strain rate between 5 × 109 s−1 and 8 × 1010 s−1, only part of the nanowire exhibits amorphous state after yielding while the other part remains crystalline state. Both the {1 1 1} slippages in ordered region and homogenous deformation in amorphous region contribute to the plastic deformation.