Ab initio study of chemical disorder as an effective stabilizing mechanism of bcc-based TiAl(+Mo)

0532800 - ÚFM 2021 RIV US eng J - Článek v odborném periodiku
Abdoshahi, N. - Spoerk-Erdely, P. - Friák, Martin - Mayer, M. - Šob, Mojmír - Holec, D.
Ab initio study of chemical disorder as an effective stabilizing mechanism of bcc-based TiAl(+Mo).
Physical Review Materials. Roč. 4, č. 10 (2020), č. článku 103604. ISSN 2475-9953. E-ISSN 2475-9953
Grant CEP: GA MŠMT(CZ) LQ1601
Institucionální podpora: RVO:68081723
Klíčová slova: TITANIUM ALUMINIDE ALLOYS * HIGHER-ENERGY PHASES * IN-SITU * TENSILE-STRENGTH * LOCAL STABILITY * BEHAVIOR * MICROSTRUCTURE * 1ST-PRINCIPLES * EQUILIBRIA
Obor OECD: Condensed matter physics (including formerly solid state physics, supercond.)
Impakt faktor: 3.989, rok: 2020
Způsob publikování: Omezený přístup
https://journals.aps.org/prmaterials/abstract/10.1103/PhysRevMaterials.4.103604

To shed a new light on the complex microstructural evolution in the Ti–Al–Mo system, we employ
ab initio calculations to study bcc-fcc structural transformations of ordered βo-TiAl(+Mo) and disordered
β-TiAl(+Mo) to ordered γ -TiAl(+Mo) and hypothetically assumed disordered γdis-TiAl(+Mo) alloys, respectively.
In particular, tetragonal (Bain’s path) and trigonal transformations are combined with the concept of
special quasirandom structures (SQS) and examined. Our calculations of the ordered phases show that the βo →
γ tetragonal transformation of TiAl is barrierless, i.e., proceeds spontaneously, reflecting the genuine structural
instability of the βo phase. Upon alloying of ≈7.4 at.%Mo, a small barrier between βo and γ -related local energy
minima is formed. Yet a higher Mo content of ≈9 at.% leads to an opposite-direction barrierless transformation
γ → βo, i.e., fully stabilizing the βo phase. Considering the disordered phases, the β-Ti0.5Al0.5−xMox and
γdis-Ti0.5Al0.5−xMox are energetically very close. Importantly, for all here-considered compositions up to 11 at.%
of Mo, a small energy barrier separates β-TiAl(+Mo) and γdis-TiAl(+Mo) energy minima. Finally, a trigonal
path was studied as an alternative transformation connecting disordered β and γdis-TiAl phases, but it turns out
that it exhibits an energy barrier over 60meV/at. which, in comparison to the Bain’s path with 9meV/at. barrier,
effectively disqualifies the trigonal transformation for the TiAl system.
Trvalý link: http://hdl.handle.net/11104/0311443