Advanced TEM investigation of the plasticity mechanisms in nanocrystalline freestanding palladium films with nanoscale twins
Advanced TEM investigation of the plasticity mechanisms in nanocrystalline freestanding palladium films with nanoscale twins
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DOI：
10.1016/j.ijplas.2012.04.003
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发表时间：
2012-10-01
影响因子：
9.8
通讯作者：
Schryvers, D.
中科院分区：
文献类型：
--
作者：
Wang, B.;Idrissi, H.;Schryvers, D.
纳米晶钯薄膜沉积的电子束蒸发和变形的片上拉伸测试显示出令人惊讶的大应变硬化能力时，考虑到小的类似25 nm的晶粒尺寸。所生长的薄膜包含几个相干的单重和多重孪晶界。由于位错/孪晶界面相互作用，孪晶界面的一致性随着变形而显著降低。这些反应是基于使用高分辨率TEM，包括像差校正显微镜位于孪晶界的位错的数量和类型的详细分析。在孪晶/基体界面处观察到无座弗兰克位错，这解释了由于伯格斯矢量指向孪晶平面之外而导致的TB相干性的损失。晶界介导的过程被排除作为主导的机制的塑性变形的基础上的晶粒尺寸分布的调查，以及使用自动晶体取向指数TEM的晶体织构。使用分析TEM研究了影响塑性变形的其他因素，例如杂质和在膜表面处的原生钝化氧化物层的存在。本工作中观察到的孪晶界面通过提供随变形而增加的位错运动阻力和位错增殖的来源，部分解释了高应变硬化能力。(C)2012爱思唯尔有限公司保留所有权利。
Nanocrystalline palladium thin films deposited by electron-beam evaporation and deformed by on-chip tensile testing reveal a surprisingly large strain hardening capacity when considering the small similar to 25 nm grain size. The as-grown films contain several coherent single and multifold twin boundaries. The coherency of the twin boundaries considerably decreases with deformation due to dislocation/twin boundary interactions. These reactions are described based on a detailed analysis of the number and the type of dislocations located at the twin boundaries using high-resolution TEM, including aberration corrected microscopy. Sessile Frank dislocations were observed at the twin/matrix interfaces, explaining the loss of the TB coherency due to the Burgers vector pointing out of the twinning plane. Grain boundary mediated processes were excluded as a mechanism dominating the plastic deformation based on the investigation of the grain size distribution as well as the crystallographic texture using Automated Crystallographic Orientation Indexation TEM. Other factors influencing the plastic deformation such as impurities and the presence of a native passivation oxide layer at the surface of the films were investigated using analytical TEM. The twin boundaries observed in the present work partly explain the high strain hardening capacity by providing both increasing resistance to dislocation motion with deformation and a source for dislocation multiplication. (C) 2012 Elsevier Ltd. All rights reserved.