Self-Organization in Model Cu Alloys for High-temperature Irradiation Environments

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TECHNICAL SUMMARY:The PIs utilize self-organization reactions to obtain materials that are intrinsically stable under high-temperature irradiation environments. Conventional materials degrade through embrittlement, segregation, creep, and swelling in such environments, caused by the unbalanced flow of point defects to sinks. In order to overcome these detrimental evolutions, self-organization reactions are used here to introduce a high density of stable point-defect traps, thus enhancing recombination. Two separate self-organization mechanisms are considered, involving the competition between ballistic mixing and thermal decomposition, and intra-cascade precipitation. By activating both mechanisms simultaneously, complex core/shell nanostructures are expected with vastly improved stability under irradiation at homologous temperatures as high as 0.80 and with improved mechanical properties. Model Cu-W-X ternary alloys (X = Ag, Fe, Ni) are used to test and validate the approach. Thin films of these alloys are characterized before and after ion irradiation with a combination of techniques, including XRD, TEM, atom probe tomography, and in situ electrical resistivity. Atomistic simulations, including kinetic Monte Carlo simulations that include the creation, recombination and elimination of point defects, are employed to identify the conditions for compositional patterns to remain dynamically stable at elevated temperature and under irradiation. The impact of the program is broadened by developing a new module for a senior laboratory course, highlighting nanoscale precipitation and ordering in thin films, by providing research experience for undergraduates, and by promoting faculty-student interactions and outreach activities through our departmental Material Advantage Chapter.NON-TECHNICAL SUMMARY:The proposed design for the future generations of advanced nuclear power systems rely on materials that need to operate at elevated temperatures and under prolonged irradiation. Current materials cannot operate safely, reliably, and economically in such harsh environments. The present research program proposes to utilize self-organization reactions to design materials that will produce complex nano-scale precipitates. By judicious choice of alloying elements, these nano-precipitates will be optimized to stabilize the microstructure and the mechanical properties of these materials. The resulting high-strength, high-temperature materials will also be of interest for other energy production systems. The research will provide education for two graduate and two undergraduate students, with an emphasis on advanced materials synthesis and characterization techniques and atomistic modeling. Special effort will be made to recruit female and underrepresented minority students. Outreach activities aimed at encouraging high-school students to pursue STEM careers will be initiated and coordinated with our departmental Material Advantage student chapter.