Collaborative Research: Elucidating High Temperature Deformation Mechanisms in Refractory Multi-Principal-Element Alloys

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

NON-TECHNICAL SUMARY Modern transportation, power generation, space access, and national security all rely on the availability of materials that can maintain their shape and strength at elevated temperatures. The development of nickel-based superalloys, which often contain ten or more elements, are used in jet engines, can withstand temperatures of over 1,000oC, and allow for gas temperatures in excess of 1,400oC. The development of multiple generations of these superalloys occurred over many decades but is reaching its limit. Further temperature advancements would result in better fuel efficiencies, greater thrust, and optimal performance, but novel approaches to alloy development are required. The use of refractory elements that have higher melting temperatures and the creation of equiatomic alloys represent two promising paths forward, but current understanding of how these new alloys deform at extreme temperatures is currently lacking. This study combines advanced computational modeling with novel ultrahigh temperature experiments and detailed electron microscopy to identify the deformation mechanisms that govern the high temperature strength of this new class of refractory multi-principal-element alloys. The proposed collaboration is both rapidly accelerating the rate of alloy discovery while providing meaningful educational and career advancement opportunities, thus expanding and enlarging the workforce in automotive, aerospace, and national defense sectors. TECHNICAL SUMMARY Refractory-multi-principal-element alloys (RMPEAs) hold tremendous potential for use as structural materials that can operate at ultrahigh temperatures (UHT) and in the extreme environments required for energy efficient power generation, hypersonic flight, and space access. Targeted use temperatures cannot be met with conventional superalloys, and current understanding of the UHT mechanical behavior of RMPEAs is still in its infancy and represents a critical impediment to the realization of this new class of alloys. The scientific merit of the proposed research is predicated on the overwhelming need to predict, characterize, and understand the deformation mechanisms that govern the mechanical response of RMPEAs at temperatures approaching 1500oC. The integration of advanced mesoscale modeling of dislocation dynamics, novel sub-scale mechanical testing, and detailed microstructural characterization are being used to gather much needed UHT tensile and creep data to develop a fundamental scientific description of the ultrahigh temperature deformation of nearly equiatomic, compositionally complex, multicomponent alloys. Participation in established programs at Johns Hopkins University and the University of California, Santa Barbara are providing research experiences for under-represented high school and undergraduate students, and the proposed undergraduate student exchanges hold real potential for expanding the pipeline of STEM graduate students, and in time, STEM leaders and role models. 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.