About this Abstract |
Meeting |
2021 TMS Annual Meeting & Exhibition
|
Symposium
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Computational Thermodynamics and Kinetics
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Presentation Title |
Vacancy-mediated Phase Selection in High-entropy Alloys |
Author(s) |
Prashant Singh, Shalabh Gupta, A V Smirnov, Matthew J Kramer, Duane D Johnson |
On-Site Speaker (Planned) |
Prashant Singh |
Abstract Scope |
We highlight the importance of vacancy-mediated stability in refractory high-entropy alloys (HEAs), where even small amounts of vacancies suppress chemical short-range order (SRO) and drive vacancy ordering. As an example, phase selection in Ti-Zr-Hf-Al alloys was investigated by in-situ high-energy X-ray diffraction, single-crystal X-ray diffraction, and density-functional-theory electronic-structure methods that address chemical disorder, including vacancies, predicting formation enthalpy, structure, density, and chemical SRO. Samples with varying Al content were synthesized, characterized, and computationally assessed to ascertain the composition-dependent phase selection, as increased Al content often acts as a stabilizer of a body-centered-cubic structure. Equiatomic TiZrHfAl was especially interesting due to its observed bcc superstructure, a variant of gamma-brass with 4 vacancies per cell. We highlight how vacancies mediate selection of this variant, driven by vacancy-atom SRO. As vacancies are inherent in processing refractory systems, similar discoveries may await in other high entropy alloys or in revisiting older experimental data. |
Proceedings Inclusion? |
Planned: |
Keywords |
High-Entropy Alloys, Characterization, Modeling and Simulation |