Insights into dislocation nucleation obtained from in-situ TEM studies and MD Simulations of deformation of single crystal and twinned Au nanowires

Cynthia Volkert, Georg-August Universität, Göttingen, Germany

Deformation of high quality Au nanowires provides a rare opportunity to gain insights into the fluctuation-controlled process of dislocation nucleation. In the initially dislocation-free nanoscale volumes of the nanowires, deformation proceeds by dislocation nucleation and typically does not involve dislocation interactions, so that the deformation microstructure and morphology can be used to gain indirect insights into dislocation creation. In this combined experimental-computational study we compare in-situ TEM observations of the evolution of microstructure and morphology during tensile deformation with MD predictions for single crystal Au nanowires and for nanowires containing a single longitudinal twin boundary. We find that many aspects of the experimental deformation morphologies are in excellent agreement with the simulations, including the occurrence of coordinated deformation twinning in both grains of the longitudinally twinned nanowires, which controls the ductility. Furthermore, simulations of effects of surface roughness on surface nucleation provide a likely explanation for the experimentally observed variation in flow stress. However, a number of experimental observations of dislocation and stacking fault annihilation while the wires are still under tension or as they fail, cannot be reproduced up until now by the simulations. Possible arguments that motivate this surprising behaviour and tactics for optimizing ductility in nanoscale volumes will be discussed.

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Session M3: Moday, 25 June 2018

Start: 04:30 p.m.
End: 05:15 p.m