Synchrotron Polychromatic X-Ray Laue Microdiffraction Study on the Microstructures of Crystalline Materials

With the advent of efficient brightness-preserving X-ray focusing optics and synchrotron radiation-based techniques, local crystal structure, orientation, microscopic elastic strain/stress, and defect type and density can all be probed with a single scan of micro-focused synchrotron polychromatic X-ray Laue diffraction (μXRD), and these microstructural features can be further related to the mechanical and physical properties of the crystals. The μXRD technique is particularly suitable for the non-destructive and quantitative mapping of the microstructural characteristics of inhomogeneous multiphase polycrystalline samples, as well as imperfect epitaxial crystals, without involving any critical sample preparation procedures. In this paper, three examples are introduced in details. First of all, the orientation distribution Nd₂Ir₂O₇ polycrystals, which are brittle and virtually impossible for fine surface polishing, are mapped using the μXRD technique and related to their unique electrical conductance distribution. Secondly, the elastic lattice strain distribution in laser 3D printed Ni-based superalloy is studied and compared to the case in cast bulk materials. Finally, the defect type (mainly dislocations) and density are thoroughly mapped from the matrix to the cladding layers of a laser 3D printed Ni-based superalloy. By studying the nano-hardness of the same region using the technique of nano-indentation, the mechanical properties are successfully linked with the dislocation densities. As μXRD enters its 20^th year of existence and new synchrotron nanodiffraction facilities are being built and commissioned around the world, two dimensional or even three dimensional scans on the testing specimens with tiny scanning steps become possible and giant amount of Laue diffraction data are collected. Therefore new data analysis algorithms and tools are being developed. In this paper we briefly review the new achievements and trends in this field. We take the opportunity to overview the current capabilities as well as the latest technical developments, and hopefully can spur more and more Chinese researchers and scientists to take advantage of the powerful μXRD materials study technique.