Investigation of fine-scale dislocation distributions at complex geometrical structures by using HR-EBSD and a comparison with conventional EBSD

Abstract

Dislocation distribution is one of the elementary factors that directly influence deformation processes in structural components. Electron backscatter diffraction (EBSD) analysis is one of the experimental techniques that allow for a semi-quantitative evaluation of the Geometrically Necessary Dislocation (GND) distribution in polycrystals. Owing to its noise floor the accuracy of conventional Hough transformed-based GND analysis is restricted to relatively large plastic strains. This problem can be overcome by using the cross-correlation-based high angular resolution electron backscatter diffraction (HR-EBSD) method. The present study demonstrates the improvements in characterizing localized dislocation distribution using the HR-EBSD method compared to the conventional approach. To demonstrate the efficacy, we investigated two more extreme examples of deformation conditions in polycrystalline zirconium (Zr), 1) a plastically deformed crack tip in presence of applied strain, and 2) a misfit plastic field around a hydride precipitate. The edge, screw and total GND components are compared for both cracked and hydride specimens. Dissimilarities in the identification of screw dislocations and subtle features with misorientation uncertainties are reported using HR-EBSD and conventional EBSD. A direct correlation between slip bands and the HR-EBSD estimated GNDs is presented, enhancing the scope of this approach to identify individual slip bands, which is traditionally challenging for any misorientation-based characterization technique.