Transition of creep mechanism in nanocrystalline metals
Transition of creep mechanism in nanocrystalline metals
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DOI：
10.1103/physrevb.84.224102
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发表时间：
2011-12-12
影响因子：
3.7
通讯作者：
Ogata, Shigenobu
中科院分区：
文献类型：
--
作者：
Wang, Yun-Jiang;Ishii, Akio;Ogata, Shigenobu
了解原子级蠕变机制对于实现纳米晶(NC)金属在较宽温度范围内的力学和热力学稳定性具有重要意义。在这里，我们报告了由竞争变形机制主导的NC铜蠕变的分子动力学分析。结果表明，随着应力的增加，蠕变机制由晶界扩散转变为晶界滑动，再转变为位错形核。推导出的应力指数、0.1-10b(3)的小激活体积和晶粒度指数都与实验值定量地吻合。我们提出了NC金属的应力-温度变形图，以适应不同应力驱动、热激活过程之间的竞争。该模型具有较强的通用性，能较好地回答NC金属的变形机制随应力变化的问题。
Understanding creep mechanisms with atomistic details is of great importance to achieve the mechanical and thermodynamical stabilities of nanocrystalline (NC) metals over a wide temperature range. Here we report a molecular dynamics analysis of creep in NC copper dominated by competing deformation mechanisms. We found the dominating creep mechanism transits from grain boundary (GB) diffusion to GB sliding, and then dislocation nucleation with increasing stress. The derived stress exponent, small activation volume of 0.1 - 10b(3), and grain size exponent all agree quantitatively with experimental values. We proposed a stress-temperature deformation map in NC metals accommodated by the competition among different stress-driven, thermally activated processes. The model is general to answer the question why deformation mechanism transits with stress in NC metals.