Chemical and Biological Engineering, Materials Science and Engineering, Physics and Astronomy, Ames Laboratory
Journal or Book Title
Phase selection in Ti-Zr-Hf-Al high-entropy alloys was investigated by in-situ high-energy X-ray diffraction, single-crystal X-ray diffraction, and density-functional theory based electronic-structure methods that address disorder and vacancies, predicting formation enthalpy and chemical short-range order (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 γ-brass with 4 vacancies per cell (not 2 as in γ-brass). We highlight how vacancy ordering mediates selection of this variant of γ-brass, which is driven by vacancy-atom SRO that dramatically suppress all atomic SRO. As vacancies are inherent in processing refractory systems, we expect that similar discoveries await in other high entropy alloys or in revisiting older experimental data.
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This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Acta Materialia Inc.
Singh, Prashant; Gupta, Shalabh; Thimmaiah, Srinivasa; Thoeny, Bryce; Ray, Pratik K.; Smirnov, Andrei V.; Johnson, Duane D.; and Kramer, Matthew J., "Vacancy-mediated complex phase selection in high entropy alloys" (2020). Materials Science and Engineering Publications. 360.
Available for download on Tuesday, May 17, 2022