Multiscale Bragg Coherent Diffraction Imaging for Polycrystals

 Bragg Coherent Diffraction Imaging (BCDI) offers a powerful approach to explorethe structure-property relationships in crystalline materials by providing three-dimensional (3D) nanoscale imaging of strain fields within individual grains and nanoparticles. This thesis delineates significant advancements in extending BCDI capabilities from single-peak to multi-peak and subsequently to multi-grain measurements. We have integrated advanced polycrystal mapping techniques such as High-Energy Diffraction Microscopy (HEDM) and scanning micro-Laue diffraction microscopy into BCDI methods to enhance materials characterization. Significant progress has been made in developing advanced indexation and screening algorithms for crystals, twins, and dislocations. Additionally, we present detailed measurements of the Ti-6Al-4V alloy at the European Synchrotron Radiation Facility (ESRF) using grain orientation and size data pre-characterized by HEDM at the Advanced Photon Source (APS). Our findings underscore the advantages of multi-grain reconstruction, particularly through the characterization of strain dynamics across grain boundaries in matrix-twin-matrix 3-grain oligocrystals of gold on strontium titanate. The ongoing enhancements to APS, which will substantially increase X-ray beam brightness, are anticipated to further facilitate rapid measurements of polycrystalline samples and the observation of dislocation movements.