In-situ Observtion of Annealing Behaviors of Bulk Metallic Polycrystals

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TECHNICAL SUMMARY: Polycrystals are ubiquitous materials that serve in extreme and mundane environments, ranging from nuclear reactors and turbine blades to structural supports and transportation infrastructure. Until recently, it has not been possible to spatially resolve relevant structural details deep inside polycrystalline materials as they evolve in response to, for example, thermal annealing. In this project focused high energy x-rays generated at the Advanced Photon Source at the Argonne National Laboratory will be used in combination with the National Science Foundation's TeraGrid supercomputer network to non-destructively measure and reconstruct the crystallographic orientation field of polycrystals in three dimensions. In well-ordered materials, crystalline grain ensembles will be observed as they evolve during annealing; both statistical and local information will be extracted from large microstructure data sets. In materials with significant defect contents, it will be possible to measure orientation gradients within grains and to watch defect structures move and evolve as the material reaches a lower energy, more ordered state. Work under this grant will advance understanding of how polycrystalline materials respond to high temperatures. The results will be used to develop improved understanding of previously hidden phenomena with the goal of establishing validated models with predictive power.NON-TECHNICAL SUMMARY: Because polycrystals are so broadly used in industrial, energy, and defense systems, the potential economic and energy impact of improved basic scientific understanding of how polycrystalline microstructures evolve during annealing can be huge. The experiments in this project will use a Department of Energy national user facility (the Advanced Photon Source at Argonne National Laboratory, one of the world's most powerful x-ray sources) while the analysis of data will involve the National Science Foundation's TeraGrid supercomputer network. The resulting data will provide a unique look at the quantities that are relevant for building theories of how materials behave. A major objective of the research is to apply the understanding gained to the development of materials with improved properties. Graduate and undergraduate students, working with faculty and post-doctoral researchers from science, mathematics and engineering departments, will be mentored. They will become skilled in x-ray science that can be applied to many materials problems and will experience the high-performance computing world. The broad impact of the experimental program will be substantially increased through interactions with the modeling community.