Vacancy formation energies and migration barriers in multi-principal element alloys

Date
2022-03
Authors
Roy, Ankit
Singh, Prashant
Balasubramanian, Ganesh
Johnson, Duane
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Elsevier
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Ames Laboratory
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Physics and Astronomy
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Materials Science and EngineeringChemical and Biological EngineeringAmes LaboratoryPhysics and Astronomy
Abstract
Multi-principal element alloys (MPEAs) continue to garner interest as structural and plasma-facing materials due to their structural (phase) stability and increased resistance to radiation damage. Despite sensitivity of mechanical behavior to irradiation and point-defect formation, there has been scant attention on understanding vacancy stability and diffusion in refractory-based MPEAs. Using density-functional theory, we examine vacancy stability and diffusion barriers in body-centered cubic (Mo0.95W0.05)0.85Ta0.10(TiZr)0.05. The results in this MPEA show strong dependence on environment, originating from local lattice distortion associated with charge-transfer between neighboring atoms that vary with different chemical environments. We find a correlation between degree of lattice distortion and migration barrier: (Ti, Zr) with less distortion have lower barriers, while (Mo, W) with larger distortion have higher barriers, depending up local environments. Under irradiation, our findings suggest that (Ti, Zr) are significantly more likely to diffuse than (Mo, W) while Ta shows intermediate effect. As such, material degradation caused by vacancy diffusion can be controlled by tuning composition of alloying elements to enhance creep strength at extreme operating temperatures and harsh conditions.
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This is a manuscript of an article published as Roy, Ankit, Prashant Singh, Ganesh Balasubramanian, and Duane D. Johnson. "Vacancy formation energies and migration barriers in multi-principal element alloys." Acta Materialia 226 (2022): 117611. DOI: 10.1016/j.actamat.2021.117611. Copyright 2022 Acta Materialia Inc. Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0). Posted with permission.
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