Molecular dynamics simulation of polycrystalline molybdenum nanowires under uniaxial tensile strain: Size effects

Abstract

The effects of grain size and length-to-diameter ratio (LDR) on deformation behaviors of polycrystalline molybdenum nanowires are studied with molecular dynamics simulations at room temperature under uniaxial tensile strain. The results show that the nanowires display the ductile characteristic through the formation of the neck and atom-thick contact before failure. We find the deformation behaviors and fractures of the nanowires that depend heavily on the grain size and LDR, and that the size-dependent deformation behavior of polycrystalline nanowires is originated from rearrangement of atomic positions with grain size and surface effect with LDR. The nanowires with smaller grain size or LDR may exhibit superplasticity behaviors due to an amorphous rearrangement of atomic positions. However, the nanowires with larger grain size and LDR rupture at the strain of 39–76% and keep most crystalline structures. For the moderate grain size nanowires, the stress–strain relation displays a distinct zigzag curve. During the plastic deformation, Mo atom with “bcc” configurations near neck can transform into other configurations due to stress-induced mechanism.