CAREER: High temperature strengthening via solute-enhanced stacking faults in structural alloys

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PART 1: NON-TECHNICAL SUMMARYSuperalloys, which are comprised of nickel with complex mixtures of other metals, are an important class of metallic high temperature structural materials used in gas turbine engines for transportation, defense, and energy generation applications. The high temperature strength of these superalloys has recently been observed to be controlled by intricate atomistic-level processes that are not well understood due to the nature of the superalloy chemistry. The basic research enabled by this CAREER award will uncover the fundamental, atomistic-level processes governing high temperature strength in model metallic materials. Computational methods and theory will be developed to provide predictive capability of these atomistic processes, and advanced characterization methods will verify those predictions. This research will enable higher strength superalloys, which could increase turbine engine efficiencies and power while decreasing pollution emissions. The fundamental insights garnered from this program will be applicable to a wide range of ceramic, metallic, and semiconductor materials used across numerous industries and could enable new technologies. Outreach efforts as part of this program will include mentoring of local High School students and materials engineering-related learning module development and dissemination.PART 2: TECHNICAL SUMMARYDespite knowledge of solute segregation to stacking faults in crystalline materials, this phenomenon has yet to be utilized as a strengthening mechanism in most structural alloy materials. Recent works in the literature and by the PI have suggested that complex dislocation interactions and minute composition differences in Ni-based superalloys control the solute segregation behavior at stacking faults, and that this segregation behavior can be utilized to increase the high temperature creep strength in Ni-based superalloys. However, due to the complex compositions in advanced superalloys the driving forces governing solute segregation are not well understood. The basic research supported by this CAREER award seeks to uncover the fundamental thermodynamic driving forces for solute segregation to stacking faults in simple alloy compositions. The objective of this work is then to predict and quantify solute segregation at stacking faults during high temperature deformation in Ni-based superalloy compositions in order to utilize Suzuki segregation to further strengthen this important class of structural materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.