Correction of artefacts associated with large area EBSD

B Winiarski; A Gholinia; K Mingard; M Gee; G Thompson; P J Withers

doi:10.1016/j.ultramic.2021.113315

Correction of artefacts associated with large area EBSD

Ultramicroscopy. 2021 Jul:226:113315. doi: 10.1016/j.ultramic.2021.113315. Epub 2021 May 14.

Authors

B Winiarski¹, A Gholinia², K Mingard³, M Gee³, G Thompson⁴, P J Withers⁵

Affiliations

¹ Department of Materials, University of Manchester, Manchester, M13 9PL, United Kingdom; Thermo Fisher Scientific, 62700 Brno, Czech Republic.
² 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. Electronic address: ali.gholinia@manchester.ac.uk.
³ Materials Division, National Physical Laboratory, Teddington, TW11 0LW, United Kingdom.
⁴ Department of Materials, University of Manchester, Manchester, M13 9PL, United Kingdom.
⁵ 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.

PMID: 34049196
DOI: 10.1016/j.ultramic.2021.113315

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. 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.

Keywords: Broad ion beam polishing; Cermet; Computed tomography (CT); Serial block face sectioning electron microscopy (SBFSEM); electron back scatter diffraction; focused ion beam (FIB).