Improving EBSD precision by orientation refinement with full pattern matching

Abstract

Summary We present a comparison of the precision of different approaches for orientation imaging using electron backscatter diffraction (EBSD) in the scanning electron microscope. We have used EBSD to image the internal structure of WC grains, which contain features due to dislocations and subgrains. We compare the conventional, Hough‐transform based orientation results from the EBSD system software with results of a high‐precision orientation refinement using simulated pattern matching at the full available detector resolution of 640 × 480 pixels. Electron channelling contrast imaging (ECCI) is used to verify the correspondence of qualitative ECCI features with the quantitative orientation data from pattern matching. For the investigated sample, this leads to an estimated pattern matching sensitivity of about 0.5 mrad (0.03°) and a spatial feature resolution of about 100 nm. In order to investigate the alternative approach of postprocessing noisy orientation data, we analyse the effects of two different types of orientation filters. Using reference features in the high‐precision pattern matching results for comparison, we find that denoising of orientation data can reduce the spatial resolution, and can lead to the creation of orientation artefacts for crystallographic features near the spatial and orientational resolution limits of EBSD.

Experimental and numerical investigation of key microstructural features influencing the localization of plastic deformation in Fe-TiB2 metal matrix composite

“…The precision of orientation measurements could be further increased with the use of techniques such as pattern matching [35,36,39] or High-Resolution EBSD (HR-EBSD) [40,41]. However, these techniques are still not adapted to large EBSD datasets.…”

Kikuchi pattern simulations of backscattered and transmitted electrons

“…Model parameters were determined via fitting to the experimental Kikuchi pattern, as described in Refs. 24 and 25 . The best‐fit parameters were determined at the maximum of the normalised cross‐correlation coefficient (NCC) between the simulated pattern and the experimental pattern.…”

“…Kikuchi diffraction simulations are also applied to estimate continuous parameters from experimental patterns. This includes the calibration of the geometrical setup, 17–20 the indexing and refinement of crystal orientations 8,21–27 and the quantification of local changes in lattice parameters, 28–31 including the possible role of defects 32 …”

Refined Calibration Model for Improving the Orientation Precision of Electron Backscatter Diffraction Maps

“…In order to obtain the experimental estimations c (i) E = (PCX i , PCY i , PCZ i , 1) of the PC coordinates from the experimental Kikuchi patterns, individual values for the orientation and the projection center c (i) E of a map point i where determined by a best-fit pattern matching approach as described in [28,42]. The best fit parameters were determined at the maximum of the normalized cross correlation coefficient (NCC) between the simulated pattern and the experimental pattern.…”

“…In addition to EBSD, the technique of electron channeling orientation determination (eCHORD) also requires an accurate knowledge of the incident beam geometry for precise orientation determination when large sample areas are scanned [22,23]. The assumption of an incorrect projection center can bias the local crystallographic parameters which are obtained by the analysis of EBSD patterns, and thus has a direct influence on the precision of orientation data from the sample, the lattice parameters, the sensitivity to pseudosymmetry issues, and the quality of phase discrimination, among other issues [20,21,[24][25][26][27][28]. In this way, the projection center is of key importance for the principle of the EBSD method, but its quantitative influence on errors of the final EBSD orientation data often is not completely transparent.…”