Journal
ACTA MATERIALIA
Volume 200, Issue -, Pages 171-186Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2020.08.034
Keywords
Thermodynamics; Phase transformations; Alloy theory; First-principles; Statistical mechanics
Funding
- ONR BRC Program [N00014-18-1-2392]
- National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility [DE-AC02-05CH11231]
- California NanoSystems Institute at UC Santa Barbara
- Materials Research Science and Engineering Center (MRSEC) at UC Santa Barbara [NSF DMR 1720256]
- National Science Foundation [CNS-1725797]
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We investigate phase stability in all binary alloys comprised of elements from groups 4 (Ti, Zr, Hf), 5 (V, Nb, Ta) and 6 (Cr, Mo, W) of the periodic table. First-principles calculations of the energy landscapes along crystallographic pathways that connect bcc to hcp and bcc to omega show that group 4 elements are very distinct from group 5 and 6 elements. While group 5 and 6 elements are stable in bcc, group 4 elements favor hcp and omega and are predicted to be dynamically unstable in bcc. A comprehensive firstprinciples investigation of the 36 refractory binary systems using statistical mechanics techniques reveals six distinct classes of alloys, each with a unique phase diagram topology. The predictions of this study are in excellent agreement with previous experimental work. One exception is a class of refractory alloys with high temperature miscibility gaps that are not predicted with the methods used in this work. Our calculations predict the stability of a low-temperature Laves phase in the Nb-V binary that has yet to be observed experimentally. The relationships between alloy chemistry and high-temperature phase stability revealed in this study provide a basis for the systematic design of multicomponent disordered refractory alloys. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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