Congratulations to Dr. David Beaudry on successfully defending his thesis, entitled “Lattice Tuning for High-temperature Performance of Refractory Multi-Principal Element Alloys”. Check out the abstract, below. Congratulations, David! We can’t wait to see what you do next!

Abstract: Refractory multi-principal element alloys (RMPEAs), which contain roughly equal proportions of three or more high-melting point elements, are candidates for the next generation of structural materials for service in high-temperature environments. However, development of these alloys has failed to yield synergy between ductility, strength, and oxidation resistance. High-temperature oxidation resistance has only been reported in RMPEAs with high volume fractions of brittle intermetallics that inhibit their processing and structural capabilities. RMPEAs with high concentrations of Mo and W have demonstrated high-temperature strength but lack both oxidation resistance and room-temperature tensile plasticity, which similarly precludes their feasibility as load-bearing components. RMPEAs with a combination of Group IV (Ti, Zr, Hf) and Group V (V, Nb, Ta) elements have been found to possess surprising ductility and toughness to cryogenic temperatures, although at the expense of high-temperature strength.

The first thrust of this work uncovered the fundamental phase evolution during oxidation of ductile Group IV-V RMPEAs which then informed design for improved oxidation resistance without sacrificing mechanical performance. The second thrust probed the effects of composition and local chemical order on the interatomic interactions, including electronic structure and lattice dynamics, that govern plasticity in BCC and refractory alloys. The third thrust produced low-cost, high-temperature precipitation strengthened RMPEAs with a novel intermetallic approach that circumvents the pitfalls of B2 precipitation in RMPEAs. The relevant properties were elucidated through sub-nanometer characterization including Transmission Electron Microscopy, Atom-Probe Tomography, and Inelastic Neutron Scattering. The insights gained in this work will allow for more targeted alloy design to promote simultaneous strength, ductility, and oxidation resistance for next-generation structural components in extreme environments.