The deformation mechanism in cold-welded gold nanowires due to dislocation emission

Abstract

Though dislocation emission was known to be critical in the deformation and fracture process of metallic nanowires, the corresponding mechanism in cold-welded metallic nanowires has never been clarified. In order to understand the dislocation-mediated deformation mechanism in cold-welded nanowires, large-scale atomistic simulations are employed in this work. During dislocation emission, the formation and motion of only unclosed shear loops are observed inside nanowires. We prove from a theoretical viewpoint that unclosed shear dislocation loops can induce material transport and hence plastically deform cold-welded nanowires. For a better clarification, through running simulation replicates, we propose a novel approach to single out the displacement field solely due to shear loop emission. Regarding the pattern of material transport, our simulated atom arrangement near the dislocation core is found consistent with that captured by high-resolution transmission electron microscopy (HRTEM) of a stressed Au nanocrystal. Our analysis clarifies that the emission of unclosed shear loop plays a crucial role in not only the tensile deformation, but also the fracture process of cold-welded nanowires. It should be regarded as a general mechanism that shear loop emission can induce surface deformation and redistribute mass in the process of plasticity.