Abstract
We use classical molecular-dynamics simulations to examine the strain-rate sensitivity of single-crystalline and twinned Au nanowires (NWs) with a diameter of 12.3 nm deformed in tension at temperatures between 10 K and 450 K. It is found that the strain-rate sensitivity above 100 K is significantly smaller in twinned Au NWs with perfectly circular cross-section than in similar NWs without twins, while the activation volume remains in the same range of with the magnitude of Burgers vector. This behavior is markedly different from that generally observed in bulk face-centered cubic metals where addition of nanoscale twins increases both strength and strain-rate sensitivity. Furthermore, our simulations show a threefold decrease in strain-rate sensitivity in twinned Au NWs with zigzag morphology constructed by assembly of {111} surface facets in comparison to the different types of circular Au NWs. The rate-controlling deformation mechanisms related to surface dislocation emission and twin-slip interaction, and their dependence on temperature and surface morphology are analyzed in detail. The combination of ultrahigh strength and decreased sensitivity to strain-rate predicted above 100 K in twinned Au NWs with faceted surface morphology holds great promise for creating metallic nanostructures with increased failure resistance to extreme loading conditions.
2 More- Received 16 December 2009
DOI:https://doi.org/10.1103/PhysRevB.81.155430
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