Enhanced EBSD calibration accuracy based on gradients of diffraction patterns

Abstract

High-resolution electron backscatter diffraction (HR-EBSD) attracts increasing attention in materials researches, and correlating simulated and experimental diffraction patterns is a major HR-EBSD branch. However, the correlation accuracy is limited by several secondary effects generally not accounted for in pattern simulations, such as the non-uniform electron energy, Kikuchi band (K-band) asymmetry or gray level reversal. Although some of these phenomena can be simulated by Monte Carlo method and dynamical simulation, the computation is highly demanding and their effects on EBSD calibration are not systematically analyzed. Recently, it has been shown that the precise locations of K-band edges were better identified using the gradient of the diffraction patterns, in particular with the presence of K-band asymmetry. In the present study, it is proposed to use a similar strategy, in Integrated Digital Image Correlation to circumvent the systematic errors, and lack of accuracy due to these asymmetry artefacts. Gray level profiles of the K-bands are analyzed to assess the correctness of image registration. High-definition experimental EBSD datasets show that crystal orientation uncertainty improves by 0.01° when using gradients. Another evidence of the enhanced calibration accuracy is the improved continuity of the calibrated projection center position at grain boundaries by about 50%. In view of these results, it is suggested to systematically use gradients of diffraction patterns in all high-resolution EBSD analyses when correlating experimental and simulated patterns.