Displacive-Diffusive plasticity in nanoporous gold nanowires under tensile creep

Abstract

While creep deformation of nanoporous gold (NPG) was argued to be mainly dislocation mediated, we show using molecular dynamics simulations of tensile creep of NPG nanowires that diffusion plays a significant role. Lower creep stress regimes are influenced by dominant atomic diffusion with negligible dislocation accumulation, while the interplay between surface diffusion and dislocation slips governs the deformation at higher creep stresses. The deformation mechanisms manifest themselves in the calculated activation volumes and creep stress exponents, which are of the same orders of those calculated from indentation creep experiments despite the different length and time scales. The contribution from the dislocation events decreases with increase in the ligament diameter, which is expressed as change in the creep exponents at the higher creep stresses. We suggest that this displacive-diffusion plasticity mechanism is essential to capture creep deformation of NPG structures.