Title
Vacancy-mediated complex phase selection in high entropy alloys
Publication Date
8-1-2020
Department
Materials Science and Engineering; Chemical and Biological Engineering; Physics and Astronomy; Ames Laboratory
Campus Units
Ames Laboratory, Chemical and Biological Engineering, Materials Science and Engineering, Physics and Astronomy
OSTI ID+
1633760
Report Number
IS-J 10125
DOI
10.1016/j.actamat.2020.04.063
Journal Title
Acta Materialia
Volume Number
194
First Page
540
Last Page
546
Abstract
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.
DOE Contract Number(s)
AC02-07CH11358
Language
en
Department of Energy Subject Categories
36 MATERIALS SCIENCE
Publisher
Iowa State University Digital Repository, Ames IA (United States)
