Effects of grain growth on grain-boundary diffusion creep by molecular-dynamics simulation |
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| Affiliation: | 1. Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong SAR, China;2. Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China;3. Hong Kong Institute for Advanced Study, City University of Hong Kong, Hong Kong SAR, China;4. Institute of Scientific Computing, TU Dresden, 01062 Dresden, Germany;5. Dresden Center for Computational Materials Science, TU Dresden, 01062 Dresden, Germany;1. Institute of Scientific Computing, TU Dresden, Dresden 01062, Germany;2. Dresden Center for Computational Materials Science, TU Dresden, Dresden 01062, Germany;3. Hong Kong Institute for Advanced Study, City University of Hong Kong, Hong Kong SAR, China;4. Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, China;5. Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong SAR, China |
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| Abstract: | Molecular-dynamics simulations are used to elucidate the effects of grain growth on grain-boundary diffusion creep and grain-boundary sliding during high-temperature deformation of a nanocrystalline Pd model microstructure. The initial microstructure consists of a 25-grain polycrystal with an average grain size of about 15 nm and a columnar grain shape. Prior to the onset of significant grain growth, the deformation proceeds via the mechanism of Coble creep accompanied by grain-boundary sliding. While grain growth is generally known to decrease the creep rate due to the increase of the average grain size, the results obtained in this study reveal an enhanced creep rate at the onset of the grain growth, when rapid grain-boundary migration occurs. The enhanced creep rate is shown to arise from topological changes during the initial growth phases, which enhance both the stress-induced grain-boundary diffusive fluxes and grain-boundary sliding. Dislocations generated as a result of grain-rotation-induced grain coalescence and grain-boundary decomposition in the vicinity of certain triple junctions also contribute to the deformation. |
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