Combination of in situ straining and ACOM TEM: A novel method for analysis of plastic deformation of nanocrystalline metals
Combination of in situ straining and ACOM TEM: A novel method for analysis of plastic deformation of nanocrystalline metals
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DOI：
10.1016/j.ultramic.2012.12.019
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发表时间：
2013-05-01
期刊：
影响因子：
2.2
通讯作者：
Kuebel, C.
中科院分区：
文献类型：
--
作者：
Kobler, A.;Kashiwar, A.;Kuebel, C.
与粗晶金属相比，纳米晶金属表现出不同的变形机制，因为随着晶粒度的减小，位错存储能力降低，晶界中介过程变得更加明显。作为一种直接成像和量化纳米晶薄膜塑性变形过程的新方法，发展了一种将微探针STEM模式下的自动晶体取向映射与透射电子显微镜内的原位应变相结合的方法。ACOM-TEM通过提供纳米分辨率的全取向图，缩小了EBSD和BF/DFTEM之间的差距。这种与原位应变相结合的新方法首次提供了在纳米尺度上直接成像和量化薄膜系综中所有微晶在机械变形过程中结构变化的可能性。用它表征了磁控溅射制备的纳米金薄膜在拉伸变形过程中的金相变化。在全球(微米尺寸范围内的平均颗粒)和局部(选定颗粒的组装)尺度上对晶粒度、晶向和孪晶的研究有助于深入了解变形过程。晶界运动和局部晶界旋转是消除外加应力的两个过程。此外，在应变过程中，孪晶/去孪晶同时发生。这些过程在当地已经发生在微塑性区域，导致了从向宏观塑性变形区域的过渡开始的全球晶粒生长。(C)2013爱思唯尔B.V.保留所有权利。
Nanocrystalline metals are expected to exhibit different deformation mechanisms when compared to their coarse grained counterparts because the dislocation storage capacity decreases and the grain boundary mediated processes become more pronounced with decreasing grain size. As a new approach to directly image and quantify the plastic deformation processes in nanocrystalline thin films, a combination of automated crystal orientation mapping in microprobe STEM mode with in situ straining inside a TEM was developed. ACOM-TEM closes the gap between EBSD and BF/DFTEM by providing full orientation maps with nanometer resolution. The novel combination with in situ straining provided for the first time the possibility to directly image and quantify the structural changes of all crystallites in the ensemble of a thin film at the nanometer scale during mechanical deformation. It was used to characterize the metallographic changes during tensile deformation of a nanocrystalline Au thin film prepared by magnetron sputtering. The investigation of the grain size, grain orientation and twinning on a global (grain average over a micron sized area) and local (assembly of selected grains) scale allowed for the development of an in depth picture of the deformation processes. Grain boundary motion and local grain rotation were two of the processes acting to dissipate the applied stress. Additionally, twinning/detwinning occurred simultaneously during straining. These processes, which occurred locally already in the micro-plastic regime, led to global grain growth starting at the transition to the macro-plastic deformation regime. (C) 2013 Elsevier B.V. All rights reserved.