Spherical Indexing of Electron Backscatter Diffraction Patterns from Additively Manufactured Materials

Traditionally Electron Backscatter Diffraction (EBSD) patterns have been analyzed using a Hough Transform approach to determine the position of the diffraction bands within the EBSD patterns to measure the interplanar angles between the crystallographic planes represented by these bands. These measured interplanar angles are then compared to a table of reference angles derived from the crystallographic information of the phase(s) of interest to determine the best-fit solution for crystal orientation and phase. Recently new approaches based on comparing experimental patterns to simulated patterns generated from dynamical diffraction models have been introduced. These approaches provide improved indexing, particularly for lower-quality EBSD patterns. One of these approaches, termed Spherical Indexing, uses cross-correlation of the experimental EBSD pattern with the dynamic simulation using a spherical harmonic transform. This technique has been successfully applied to several severely plastically deformed materials to evaluate the effectiveness of this approach. For additive manufacturing, an orientation refinement routine can also be applied to improve the orientation precision performance relative to traditional Hough-based EBSD. This performance allows for better characterization and visualization of the deformed microstructure present in additively manufactured builds. This presentation will review the Spherical Indexing approach, and present results on different additively manufactured materials.