Physics (Internal)

High Energy X-ray Diffraction Microscopy: Direct Observation of 3D Materials Responses

This event is part of the Biophysics/Condensed Matter Seminar Series.

Abstract: Spatially resolved diffraction of high energy (> 50 keV) monochromatic x-rays is used to non-destructively map microstructure inside of bulk polycrystalline materials. Tracking of structural responses to thermal and mechanical processes allows direct comparisons to computational models; such comparisons have not previously been possible because spatially resolved measurements inside of bulk materials have not been possible. Our measurements take advantage of the unique properties of x-ray beams available at the 1-ID high energy beamline at the Advanced Photon Source, Argonne National Laboratory; facilities have also been developed at other high energy, third generation synchrotrons. Measurements spanning volumes of the order of a cubic millimeter with micron scale resolution generate large, statistically significant data sets. We use a computationally intensive method to reconstruct the crystal lattice orientation field. Using repeated measurements of the same material volume allows the extraction of trends in the response behavior: grain boundary motions, grain rotations, and intra-granular defect accumulation. In this seminar I will outline the measurement and reconstruction methods and give example applications. Three-dimensional anisotropic ordering and coarsening induced by annealing are followed in pure aluminum and pure nickel samples. Twinning transformations and lattice rotations are followed in hexagonal zirconium as it undergoes tensile extension. Finally, on-going developments in the measurement and analysis methods will be summarized.