Nano-sized twins induce high rate sensitivity of flow stress in pure copper

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	Nano-sized twins induce high rate sensitivity of flow stress in pure copper
	L. Lu; R. Schwaiger; Z. W. Shan; M. Dao; K. Lu; S. Suresh
	2005
发表期刊	Acta Materialia
ISSN	1359-6454
卷号	53 期号:7 页码:2169-2179
摘要	We have investigated the rate sensitivity of flow stress and the extent of strengthening in polycrystalline copper containing different volume fractions of nano-sized twins, but having the same average grain size. The specimens were produced by pulsed electrodeposition, wherein the concentration of twins was varied systematically by varying the processing parameters. Depth-sensing instrumented indentation experiments performed at loading rates spanning three orders of magnitude on specimens with the higher density of twins (twin lamellae width similar to 20 nm) revealed an up to sevenfold increase in rate-sensitivity of hardness compared to an essentially twin-free pure Cu of the same grain size. A reduction in twin density for the same grain size (with twin lamellae width similar to 90 nm) also resulted in a noticeable reduction in rate-sensitivity and hardness. The presence of a high density of nano-scale twins is also seen to impart significant hardness, which is comparable to that achieved in nano-grained Cu. Post-indentation analyses of indented Cu with nano-scale twins in the transmission electron microscope reveal deformation-induced displacement of coherent twin boundaries (CTBs), formation of steps and jogs along CTBs, and blockage of dislocations at CTBs. These processes appear to significantly influence the evolution of thermal activation volume for plastic flow which is some three orders of magnitude smaller than that known for micro crystalline Cu. Transmission electron microscopy also reveals CTBs with a high density of dislocation debris and points to the possibility that displaced CTBs may serve as barriers to dislocation motion and that they may also provide sources for dislocation nucleation, especially near stress concentrations, very much like grain boundaries. Possible consequences of these trends for deformation are explored. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
部门归属	mit, dept mat sci & engn, cambridge, ma 02139 usa. chinese acad sci, met res inst, shenyang natl lab mat sci, shenyang 110016, peoples r china. forschungszentrum karlsruhe, inst mat res 2, d-76133 karlsruhe, germany. univ pittsburgh, dept mech engn, pittsburgh, pa 15261 usa.;suresh, s (reprint author), mit, dept mat sci & engn, cambridge, ma 02139 usa;ssuresh@mit.edu
关键词	Nanostructured Metals Twins Copper Nanoindentation Rate Sensitivity Activation Volume Strain-rate Sensitivity Thermally-activated Deformation Nanocrystalline Metals Dislocation Nucleation Tensile Behavior Grain Sizes Fcc Metals Crack Tips Bcc Metals Ductility
URL	查看原文
文献类型	期刊论文
条目标识符	http://ir.imr.ac.cn/handle/321006/40021
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	L. Lu,R. Schwaiger,Z. W. Shan,et al. Nano-sized twins induce high rate sensitivity of flow stress in pure copper[J]. Acta Materialia,2005,53(7):2169-2179.
APA	L. Lu,R. Schwaiger,Z. W. Shan,M. Dao,K. Lu,&S. Suresh.(2005).Nano-sized twins induce high rate sensitivity of flow stress in pure copper.Acta Materialia,53(7),2169-2179.
MLA	L. Lu,et al."Nano-sized twins induce high rate sensitivity of flow stress in pure copper".Acta Materialia 53.7(2005):2169-2179.