Enhanced strain-rate sensitivity in fcc nanocrystals due to grain-boundary diffusion and sliding
Enhanced strain-rate sensitivity in fcc nanocrystals due to grain-boundary diffusion and sliding
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DOI：
10.1016/j.actamat.2007.12.028
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发表时间：
2008-05
期刊：
影响因子：
9.4
通讯作者：
Yujie Wei;A. Bower;Huajian Gao
中科院分区：
文献类型：
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作者：
Yujie Wei;A. Bower;Huajian Gao
最近的实验面心立方（fcc）和六方密排（hcp）纳米晶金属报道增加了超过10倍的应变率敏感性，与传统的粗晶粒的同行。为了提高我们对这个问题的理解，我们考虑一个介观连续模型的二维多晶体的变形机制，包括晶粒内部塑性，晶界扩散和晶界滑动。该模型捕获的过渡，从滑动和扩散为主的蠕变在纳米晶体中具有相对较小的晶粒尺寸在低应变速率的塑性为主的流动在纳米晶体中具有较大的晶粒尺寸在较高的应变速率。从我们的计算得到的应变率敏感性匹配以及与纳米晶铜的实验数据。在此基础上，提出了一个分析模型，结合晶粒内部塑性和晶界变形机制之间的竞争，提供了一个直观的理解过渡的应变率敏感性的纳米结构金属。
Recent experiments on face-centered cubic (fcc) and hexagonal close packed (hcp) nanocrystalline metals reported an increase of more than 10-fold in strain-rate sensitivity in contrast to their conventional coarse-grained counterparts. To improve our understanding of this issue, we consider a mesoscopic continuum model of a two-dimensional polycrystal with deformation mechanisms including grain interior plasticity, grain-boundary diffusion and grain-boundary sliding. The model captures the transition from sliding- and diffusion-dominated creep in nanocrystals with relatively small grain sizes at low strain rates to plasticity-dominated flow in nanocrystals with larger grain sizes at higher strain rates. The strain-rate sensitivity obtained from our calculations matches well with the experimental data for nanocrystalline Cu. Based on this analysis, an analytical model incorporating the competition between grain interior plasticity and grain-boundary deformation mechanisms is proposed to provide an intuitive understanding of the transition in strain-rate sensitivity in nanostructured metals.