ERI: Mechanical Behavior of Dualphase Complex Concentrated Alloys at Elevated Temperatures

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).This Engineering Research Initiative (ERI) project is to study a special type of alloy called complex concentrated alloys (CCAs). CCAs are materials recently found to have superior mechanical properties. Materials that have high strength at high temperature are highly desirable for many engineering applications. CCAs consist of multiple principal elements and include high-entropy alloys, which contain five or more principal elements. CCAs have been researched as potential structural alloys for high temperature applications, such as heat exchangers, gas turbines, and nuclear reactors. Generally, single-phase face-centered cubic CCAs have low strength at high temperatures. Meanwhile, single-phase body-centered cubic CCAs are brittle at room temperature. Dualphase (face-centered cubic and body-centered cubic) CCAs capture the best of the features. They can exhibit both good ductility at room temperature and high strength at high temperatures. However, the current understanding of the mechanical behavior in dualphase CCAs is limited. This project aims to investigate mechanical behaviors and find the best ways to improve the strengths of dualphase CCAs at various temperatures. The knowledge learned from this project could lead to the design of dualphase CCAs for high temperature applications. The multi-disciplinary research will provide graduate students with diverse training in various engineering fields. This project will also positively impact research opportunities of underrepresented groups and engineering education.The objective of this project is to fundamentally understand how interface, microstructure, and chemistry affect the strength and deformability of dualphase CCAs from room temperature to high temperatures. Specifically, the PI will (1) investigate the interplay between temperature-dependent barrier strength of face-centered cubic and body-centered cubic CCAs; (2) reveal the role of interface on dislocation transmission and plasticity transfer between phases; (3) elucidate the effects of dislocation activities on fracture resistance of dualphase CCAs. To address these scientific questions, this project will employ site-specific nanoindentation to probe the mechanical behavior and deformation mechanisms in dualphase CCAs at various temperatures and perform detailed surface morphology and microstructure characterization through high resolution scanning probe microscopy and electron microscopy. The results of this project can provide knowledge to alleviate the brittle failure of body-centered cubic CCAs at room temperature through interfaces and enhance the high temperature strength of dualphase CCAs.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.