Effects of ternary additions on the twin energy and site preference in [gamma]--TiAl

Journal Article · Fri Jul 01 04:00:00 EDT 1994 · Journal of Materials Research; (United States)

DOI:https://doi.org/10.1557/JMR.1994.1755· OSTI ID:7175468

Xu, J ^[1]; Freeman, A J ^[2]

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1. Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208-3112 (United States)
2. Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208-3112 (United States) Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

Site preference and the effects of ternary additions (Mn, V, etc.) on the twin energy in [gamma]--TiAl were studied by means of all-electron total energy self-consistent calculations based on the local density approximation. The results show that when Mn, Ti, or V substitute on the Al-sites in [gamma]--TiAl, the twin energy is about 20--25% lower than that of stoichiometric [gamma]-TiAl; this may explain observations of increased twinning activity in 48% Al TiAl. By contrast, when ternary additions of V (or Al) occupy Ti-sites, the twin energy has nearly the same value as that of pure [gamma]--TiAl, which is consistent with the observation of only a few twins for Al-rich compositions. By comparing the total energy of Ti[sub 6](XAl[sub 5]) and (Ti[sub 5]X)Al[sub 6] supercells, it is found that the relative stability of Ti[sub 6](XAl[sub 5]) over (Ti[sub 5]X)Al[sub 6] (i.e., the preference for occupying Al-sites) is increased in going from Nb, V, Cr and Ti to Mn, in agreement with observation that excess Ti occupies Al-sites, and Nb preferentially substitutes on the Ti-sites. The results indicate that Mn preferentially substitutes on the Al-sites, and V (or Cr) may occupy both Ti-and Al-sites.

• DOE Contract Number: FG02-88ER45372
• OSTI ID: 7175468
• Journal Information: Journal of Materials Research; (United States), Journal Name: Journal of Materials Research; (United States) Vol. 9:7; ISSN JMREEE; ISSN 0884-2914
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
664100 -- Theory of Electronic Structure of Atoms & Molecules-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ALLOYS
ALUMINIUM ALLOYS
ELECTRONIC STRUCTURE
ENERGY
MANGANESE ADDITIONS
MANGANESE ALLOYS
SELF-CONSISTENT FIELD
TITANIUM ALLOYS
TWINNING
VANADIUM ADDITIONS
VANADIUM ALLOYS