Assessment of local deformation using EBSD: Quantification of accuracy of measurement and definition of local gradient

Electron backscatter diffraction (EBSD) in conjunction with scanning electron microscopy was used to assess the magnitude of microstructural scale deformation (local deformation) for deformed Type 316 stainless steel. Local misorientation, which is an averaged misorientation between neighboring measurement points, is often used for assessment of local deformation. However, the local misorientation is unsuitable for a quantitative evaluation because it depends not only on the local deformation but also on various factors such as measurement accuracy and the distance between points used in the misorientation calculation (step size). In this study, first, the measurement accuracy was quantified by a parameter called background noise. The factors which affect the measurement accuracy were then discussed from measurements under various conditions. Secondly, in order to reduce the influence of measurement conditions and exclude the dependency of step size in the local deformation assessment, a parameter called the local gradient GL was proposed. The local gradient clearly showed the spatial distribution of local deformation regardless of the measurement accuracy, and it had hardly any effect from grid pattern and step size. Finally, the local gradient was correlated with the plastic strain from which it was revealed that the strain gradient near a notch root could be estimated by the EBSD measurement.