Correction of artefacts associated with large area EBSD

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 WC-Co hardmetal. Longrange distortions (due to drift) equating to around 10 mu m across a 200 mu m x 175 mu m area map, and short-range distortions (due to topographical effects) as large as 3 mu m over a distance of 40 & micro;m 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.

Automated summary

Large 2D or 3D EBSD maps may contain distortions, including long-range distortions caused by drift and short-range artefacts from topographical features. SEM calibrations and sample alignment can minimize geometrical distortions, but long-range distortions become more prevalent in large 2D EBSD maps. Correcting these distortions is necessary for proper interpretation of morphological features in large 3D EBSD datasets.