Stress relaxation and the structure size-dependence of plastic deformation in nanotwinned copper
Stress relaxation and the structure size-dependence of plastic deformation in nanotwinned copper
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DOI：
10.1016/j.actamat.2009.07.018
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发表时间：
2009-10-01
期刊：
影响因子：
9.4
通讯作者：
Suresh, Subra
中科院分区：
文献类型：
--
作者：
Lu, Lei;Zhu, Ting;Suresh, Subra
对纳米孪晶铜进行了应力松弛实验，以表征激活体积和可移动位错密度对孪晶尺寸的依赖关系。我们发现，激活体积随孪晶厚度的变化可以很好地用Hall-Petch型关系来描述。这种结构尺寸依赖性被解释为，随着孪晶厚度的减小，速率控制机制从孪晶内向孪晶边界介导的过程转变。此外，我们还发现移动位错的耗尽率随着孪晶厚度的减小而减小。这种孪晶尺寸依赖性归因于与高密度的共格孪晶边界相关的高应变硬化速率。结果表明，孪晶界介质位错过程能有效地促进应变硬化并保留可移动位错，从而在保持塑性的同时获得超高强度。(C)2009年Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
Stress-relaxation experiments were performed on nanotwinned Cu to characterize the twin size-dependence of the activation volume and mobile dislocation density. We find that the variation of activation volume as a function of twin lamellae thickness can be captured well by a Hall-Petch-type relation. This structure size-dependence is interpreted to arise from a transition of the rate-controlling mechanism from intra-twin to twin boundary-mediated processes with decreasing twin thickness. Furthermore, we find that the exhaustion rate of mobile dislocations reduces with decreasing twin thickness. Such a twin size-dependence is attributed to the increased strain-hardening rate associated with a high density of coherent twin boundaries. Our results demonstrate that twin boundary-mediated dislocation processes can effectively promote the strain hardening and preserve mobile dislocations, leading to ultrahigh strength while retaining ductility in nanotwinned Cu. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.