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Materials Science Seminar Series presents Professor Easo George on Thursday, October 5, from 4 to 5 p.m. The seminar is hosted by Professor Hyunseok Oh and will be held in MS&E building room 265. Prof. Easo George will be discussing High-entropy alloys: where do we stand and what are the prospects?
Conventional alloys consist of a primary element chosen with a primary property in mind (e.g., gold for luster) to which secondary elements are added for other properties (e.g., copper to add strength in jewelry). Over the last two decades, a new alloy design strategy has been in vogue where 3-5 elements are mixed in near-equal amounts resulting in alloys with no primary element. These alloys are referred to as high- or medium-entropy alloys after their ideal mixing entropies. Initially, high configurational entropies were thought to not only stabilize single-phase solid solutions but also promote superior mechanical properties. However, our work has shown that is rarely the case. Nevertheless, they are scientifically interesting because textbook theories of dilute solutions break down in concentrated alloys lacking “solvents” or “solutes” in the traditional sense. A handful also exhibit striking mechanical properties at cryogenic temperatures, including strength, ductility, and toughness that are simultaneously enhanced, unlike in conventional materials where they must be traded off. I will also discuss their high-temperature behavior and show that they have a long way to go before being able to surpass state-of-the-art Ni-base superalloys. By reviewing what we have learned about the phase stability and mechanical properties of a few model systems, I hope to show that it is possible to gain broader mechanistic understanding of certain properties and phenomena that will serve as a useful guide in the hunt for next-generation alloys.
Easo George earned his PhD in materials science and engineering from the University of Pennsylvania (1985) and BTech in metallurgical engineering from IIT-Kanpur (1981). Currently, he is Em. Prof. at the University of Tennessee (UT) in Knoxville and apl. Prof. at the Ruhr-Universität Bochum (RUB) in Germany. Prior to that he was the Governor’s Chair for advanced alloy theory and development at Oak Ridge National Laboratory (ORNL) and UT (2017-2022), Professor of Materials Design and Director of the Center for Interface Dominated High Performance Materials at RUB (2017-2022), and a distinguished scientist and leader of the alloy behavior and design group at ORNL (1987-2014). George’s research interests include the physical metallurgy and mechanical properties of high-entropy alloys, iridium alloys used in radioisotope thermoelectric generators that power interplanetary spacecraft, size effects on mechanical behavior, and materials such as intermetallics and refractory metals for high-temperature applications. Among his awards and recognitions are the following: US DOE Secretary’s Honors Award for the Mars 2020 Perseverance Rover Radioisotope Power Systems Team (2022); Clarivate (Web of Science) Highly Cited Researcher (2021); Eminent Scholar Visitation Award: University of New South Wales, Sydney (2019); Invitation Fellowship for Senior Scientists: Japan Society for the Promotion of Science (2013); Elsevier award for top cited paper in Scripta Materialia during 2007-2011; TMS Fellow (2010); Humboldt-Forschungspreis, Alexander von Humboldt Foundation (2000).