Temperature-induced martensitic phase transitions in gum-metal approximants: First-principles investigations for Ti(3)Nb
- Author(s)
- Petr Lazar, Michal Jahnatek, Juergen Hafner, Naoyuki Nagasako, Ryoji Asahi, Claudia Blaas-Schenner, Markus Stöhr, Raimund Podloucky
- Abstract
We present a first-principles investigation of the structures and the dynamical stability of the austenite and martensite phases of binary Ti(3)Nb alloys, used as a model system for the superelastic and superplastic gum-metal alloy. For the body-centered cubic high-temperature beta phase, structural models are constructed by optimizing the chemical decoration of a large supercell and by a cluster expansion method. The energetically most favorable structure is found to be elastically stable but dynamically unstable in the harmonic approximation. At finite temperature anharmonic phonon-phonon interactions treated in a self-consistent phonon approximation stabilize the structure already at room temperature. For the low-temperature alpha', omega, and alpha '' phases stable structure models have been constructed. For the hexagonal alpha' phase a model is generated by optimizing the chemical decoration of a supercell based on the hexagonal B(h) lattice. The hexagonal omega structure may be derived from the body-centered cubic beta phase using the (111) plane collapse model. The structure of the orthorhombic alpha '' phase may be viewed as produced by a strain-induced transformation of the body-centered cubic beta phase, albeit with a different chemical decoration. The relaxed structures of the alpha', omega, and alpha '' phases were found to be both elastically and dynamically stable in the low-temperature limit. The martensitic temperatures for the beta -> alpha '', beta -> omega, and beta -> alpha' transitions were estimated by comparing the Helmholtz free energies as a function of temperature.
- Organisation(s)
- Computational Materials Physics, Department of Physical Chemistry
- External organisation(s)
- Toyota Central R&D Labs., Inc.
- Journal
- Physical Review B
- Volume
- 84
- No. of pages
- 17
- ISSN
- 1098-0121
- DOI
- https://doi.org/10.1103/PhysRevB.84.054202
- Publication date
- 2011
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 104017 Physical chemistry, 103018 Materials physics
- Portal url
- https://ucris.univie.ac.at/portal/en/publications/temperatureinduced-martensitic-phase-transitions-in-gummetal-approximants-firstprinciples-investigations-for-ti3nb(29af94c7-1187-4cc4-b03a-f6cdb14169c6).html