January 18 @ 3:30 pm - 4:30 pm
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High Energy X-ray Diffraction Microscopy Study of Coarsening in Iron
Robert M. Suter
Professor of Physics, Carnegie Mellon University
High energy x-ray diffraction microscopy (HEDM) allows the imaging of large numbers of crystalline grains inside of bulk polycrystalline materials. Sensitivity to grain shapes, locations, and unit cell orientations and strain states yields unique three dimensional maps with micron spatial resolution in data sets spanning cubic millimeter volumes. Since the measurements are non-destructive, responses of microstructures to applied thermal, mechanical, or other excitation fields can be tracked. This talk will begin with a summary of current practice in data collection and reconstruction of microstructures. Application of HEDM to thermally induced coarsening in an iron sample will be presented. This work, based on the mapping of several thousand grains, indicates that while isotropic models of grain boundary motion can describe average evolution properties, more detailed models that include the variation of boundary energy and mobility over the space of grain boundary character will be required to predict even which grains will grow and which will shrink, much less the extent of such changes. Finally, an NSF/MRI funded project to build a second, “high throughput,” dedicated HEDM instrument at the Advanced Photon Source will be described.
Suter has been Professor of Physics at Carnegie Mellon University for over 35 years with a courtesy appointment in Materials Science and Engineering since 2006; he recently became an Emeritus Professor but maintains an active research program. Over his career he has applied x-ray diffraction and reflection to the study of two dimensional phases adsorbed on surfaces, complex surfactant fluid thin films, and lipid membrane systems. Most recently, his research group has been instrumental in the development and application of high energy x-ray methods for the study of polycrystalline materials. His group, in collaboration with staff at Sector 1 of the Advanced Photon Source (APS) at Argonne National Laboratory, has developed both hardware and software for near-field High Energy Diffraction Microscopy (nf-HEDM) measurements. Algorithms and codes for applying high performance computing to the reconstruction of microstructures from large sets of diffraction images have been developed and made available to the user community. The group at Carnegie Mellon has applied the nf-HEDM technique to study both thermal and mechanical responses of microstructures. Current work focuses on accelerating data collection, broadening the range of applicability and information extracted. Suter has been active in developing the scientific justification for the Upgrade of the APS facility and he currently leads a consortium, funded by the NSF Major Research Infrastructure program, which is building a new high throughput HEDM instrument at the Advanced Photon Source.