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)

Share

COinS