Combined size and texture-dependent deformation and strengthening mechanisms in Zr/Nb nano-multilayers
Combined size and texture-dependent deformation and strengthening mechanisms in Zr/Nb nano-multilayers
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DOI：
10.1016/j.actamat.2016.11.007
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发表时间：
2017-02-01
期刊：
影响因子：
9.4
通讯作者：
Polcar, T.
中科院分区：
文献类型：
--
作者：
Callisti, M.;Polcar, T.
结合透射电子显微镜分析和纳米力学测量，在这项研究中进行，以揭示发生在溅射Zr/ Nb纳米金属多层膜（Nb）与周期（L）在6-167 nm的范围内的变形和强化机制。电子衍射分析表明，当L <60 nm时，α-Zr的晶体取向发生了变化，其强化机制符合Hall-Petch模型，而当27 < L < 60 nm时，则符合改进的CLS模型。当L < 27 nm时，强度降低，这不能简单地用失配和Koehler应力来解释。对于L < 27 nm，在压缩的N2 O3上测量的塑性应变揭示了α-Zr的塑性行为的变化，其经历了硬到软的转变。在这些长度尺度下，发现两个结构因素的组合影响强度。这些与较弱界面的形成有关，这些界面延长了强势垒之间的有效距离，从而产生软化效应。第二个效应与α-Zr在L < 27 nm时表现出的晶体取向变化有关，从而导致主导滑移系的变化。通过在界面屏障强度模型中考虑这些结构方面，有效地量化了这些较小长度尺度下的实际强度。(c)2016 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
A combination of transmission electron microscopy analyses and nanomechanical measurements was performed in this study to reveal deformation and strengthening mechanisms occurring in sputtered Zr/ Nb nanoscale metallic multilayers (NMMs) with a periodicity (L) in the range 6-167 nm. Electron diffraction analyses revealed a change in the crystallographic orientation of alpha-Zr when L 60 nm, the strengthening mechanism is well described by the Hall-Petch model, while for 27 < L < 60 nm the refined CLS model comes into picture. A decrease in strength is found for L < 27 nm, which could not be simply explained by considering only misfit and Koehler stresses. For L < 27 nm, plastic strain measured across compressed NMMs revealed a change in the plastic behaviour of alpha-Zr, which experienced a hard-to-soft transition. At these length scales, the combination of two structural factors was found to affect the strength. These relate to the formation of weaker interfaces which extend the effective distance between strong barriers against dislocation transmission, thus producing a softening effect. The second effect relates to the crystallographic orientation change exhibited by alpha-Zr for L < 27 nm with a consequent change of the dominant slip system. The actual strength at these smaller length scales was effectively quantified by taking these structural aspects into account in the interface barrier strength model. (c) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.