A statistical study of the relationship between plastic strain and lattice misorientation on the surface of a deformed Ni-based superalloy
A statistical study of the relationship between plastic strain and lattice misorientation on the surface of a deformed Ni-based superalloy
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DOI：
10.1016/j.actamat.2020.05.029
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发表时间：
2020-08-15
期刊：
影响因子：
9.4
通讯作者：
da Fonseca, J. Quinta
中科院分区：
文献类型：
--
作者：
Harte, A.;Atkinson, M.;da Fonseca, J. Quinta
电子背散射衍射 (EBSD) 的定向误差数据通常用于识别应变局部化并量化微观结构尺度的塑性应变。然而，局部塑性应变和取向差之间的确切关系以及它在晶粒和亚晶粒水平上如何变化尚未得到详细研究。我们使用高分辨率数字图像相关 (HRDIC) 来测量应变达 2% 的镍高温合金表面的亚微米级塑性应变。应变值与数百个晶粒的晶粒和亚晶粒尺度上的不同取向差测量相关。我们表明，尽管晶粒平均塑性应变与晶格取向差呈正相关，但相关性存在很大的分散性，这取决于所使用的取向差测量。晶粒应变的大小和晶粒取向导出的参数（例如施密德因子和泰勒因子）之间基本上也没有相关性，这主要是由于介观尺度的变形带不是晶体学的。在这些应变水平下，取向差和塑性应变之间的关系受到滑移（不连续）和晶格旋转（连续）发展方式差异、局部晶粒相互作用和跨晶应变局域化发展的影响。因此，实际上不可能仅使用 EBSD 导出的取向差值来量化单个晶粒内的塑性应变，尽管如果了解潜在的局部塑性现象，一些取向差的测量方法比其他方法更合适。尽管滑移集中在滑移带中，但取向差以与滑移仅在空间上微弱相关的方式平滑变化。这些发现对于使用连续介质力学在微观结构尺度上模拟多晶金属的变形状态具有重要意义。 (C) 2020 Acta Materialia Inc. 由 Elsevier Ltd 出版。
Misorientation data from Electron Backscatter Diffraction (EBSD) is often used to identify strain localisation and quantify plastic strain at the microstructural scale. However, the exact relationship between local plastic strain and misorientation and how it changes at the grain and sub-grain level has not been studied in detail. We have used high resolution digital image correlation (HRDIC) to measure plastic strain at the sub-micron scale on the surface of a nickel superalloy strained to 2%. The strain values have been correlated to different misorientation measures at the grain and subgrain scale, over several hundreds of grains. We show that although the grain mean plastic strain is positively correlated to the lattice misorientation, there is a large scatter in the correlation, which depends on the misorientation measure used. There is also essentially no correlation between the magnitude of grain strain and grain orientation derived parameters like the Schmid factor and the Taylor factor, largely due to deformation bands at the mesoscale that are not crystallographic. At these strain levels, the relationship between misorientation and plastic strain is affected by the differences in how slip (discontinuous) and lattice rotation (continuous) develop, by local grain interactions and the development of transgranular strain localisation. It is therefore effectively not possible to quantify plastic strain within individual grains using EBSD derived misorientation values alone, although some measures of misorientation are more appropriate than others if there is an understanding of the underlying local plastic phenomena. Whereas slip is localised in slip bands, the misorientation varies smoothly in a manner that is only weakly spatially correlated to the slip. These findings have implications for the modelling of the deformed state of polycrystalline metals at the microstructural scale using continuum mechanics. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd.