Winiarski B, Gholinia A, Mingard K, Gee M, Thompson G, Withers P J
Department of Materials, University of Manchester, Manchester, M13 9PL, United Kingdom; Thermo Fisher Scientific, 62700 Brno, Czech Republic.
Department of Materials, University of Manchester, Manchester, M13 9PL, United Kingdom; Henry Royce Institute, Department of Materials, University of Manchester, Manchester, M13 9PL, United Kingdom.
Ultramicroscopy. 2021 Jul;226:113315. doi: 10.1016/j.ultramic.2021.113315. Epub 2021 May 14.
There is an increasing requirement for the acquisition of large two (2D) or three (3D) dimensional electron back scattered diffraction (EBSD) maps. It is a well-known, but largely neglected fact, that EBSD maps may contain distortions. These include long-range distortions, which can be caused by the interaction of the electron beam with the sample geometry and it can also arise from sample or beam drift. In addition there are shorter range artefacts arising from topographical features, such as curtaining. The geometrical distortions can be minimised by careful SEM calibrations and sample alignment. However, the long-range distortions become increasingly prevalent when acquiring large area 2D EBSD maps which take a long time to acquire and thus are especially prone to drift. These distortions are especially evident in serial section tomography (SST) when 2D maps are stacked on top of one another to produce 3D maps. Here we quantify these distortions for large area EBSD data by referencing them to secondary electron (SE) images for 3D-EBSD data acquired on a WCCo hardmetal. Long-range distortions (due to drift) equating to around 10μm across a 200μm x 175 μm area map, and short-range distortions (due to topographical effects) as large as 3 μm over a distance of 40 µm were observed. Methods for correcting these distortions are then proposed. This study illustrates the benefits and necessity of such corrections if morphological features are to be properly interpreted when collecting large 3D EBSD datasets, for example by mechanical sectioning, serial block face SEM ultramicrotomy, laser sectioning, FIB-SEM tomography, PFIB spin milling, etc.
获取大面积二维（2D）或三维（3D）电子背散射衍射（EBSD）图谱的需求日益增加。EBSD图谱可能包含畸变，这是一个众所周知但在很大程度上被忽视的事实。这些畸变包括长程畸变，其可能由电子束与样品几何形状的相互作用引起，也可能源于样品或电子束漂移。此外，还有由地形特征引起的短程伪像，例如拖尾现象。通过仔细的扫描电子显微镜（SEM）校准和样品对齐，可以将几何畸变降至最低。然而，在获取大面积2D EBSD图谱时，长程畸变变得越来越普遍，因为获取这些图谱需要很长时间，因此特别容易发生漂移。当将2D图谱堆叠在一起以生成3D图谱时，这些畸变在连续切片断层扫描（SST）中尤为明显。在这里，我们通过将大面积EBSD数据的畸变与在WC-Co硬质合金上采集的3D-EBSD数据的二次电子（SE）图像进行对比，对这些畸变进行了量化。在一个200μm×175μm的区域图谱中，观察到长程畸变（由于漂移）相当于约10μm，在40μm的距离上短程畸变（由于地形效应）高达3μm。然后提出了校正这些畸变的方法。这项研究表明，如果要在收集大型3D EBSD数据集时正确解释形态特征，例如通过机械切片、连续块面SEM超薄切片、激光切片、聚焦离子束扫描电子显微镜断层扫描、等离子聚焦离子束旋转铣削等方法，进行此类校正的好处和必要性。
