Correction of artefacts associated with large area EBSD

Abstract 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. There are long-range distortions, which can be caused by the interaction of the sample and the beam geometry and it can also arise from sample or beam drift. In addition there are shorter range artefacts arising from topological 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. Long-range distortions (due to drift) equating to around 10μm across a 200μm x 175μm area map, and short-range distortions (due to topographical effects) as large as 3μm over a distance of 40 microns 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.