Atomistic modeling of plastic deformation in BCC niobium nanowire under bending

Abstract

Design of high-performance nanodevices require nanowires with optimized bending properties, which relies on a thorough understanding of the mechanical behavior of nanowires. To explore the mechanism underlying bending plasticity of the nanowire, we adopted a 〈110〉-oriented body-centered cubic (BCC) Nb nanowire as the model system and performed bending tests at various temperatures by means of molecular dynamics simulation. Our results reveal that the BCC Nb nanowire bends plastically and homogeneously into a smoothed arc shape with significant curvature by slip of perfect dislocations, showing excellent bending plasticity and toughness. The generated dislocations are identified as geometrically necessary dislocation for accommodating the strain gradient related to bending, and they accumulate linearly with the bending angle to a value of an order of 1017 m−2. Temperature dependence was found in both elastic modulus and yield strength of the nanowire. In particular, we find that a completely dislocation-mediated plasticity at high temperature changes into a deformation mechanism involving predominant dislocation slip plus additional anti-twinning as temperature is reduced. Both development of high dislocation density and reduced mobility of dislocation at low temperature contribute to the initiation of anti-twinning. Our findings not only enrich the current understanding of deformation behavior of BCC nanomaterials under non-uniaxial load, but also provide valuable information for design of flexible and stretchable nanodevices based on metallic nanowires.