Phase-stability study of the Al-Nb system
- Laboratoire de Physique Numerique des Systemes Complexes (CNRS), Maison des Magisteres, CNRS B.P. 166, 38042 Grenoble (France)
- Materials Modelling Laboratory, Department of Materials, University of Oxford, OX1 3PH Oxford (United Kingdom)
- Department of Materials Science and Engineering, University of Surrey, Surrey GU2 5XH (United Kingdom)
The total energies of formation of Al-Nb intermetallic phases Nb{sub 3}Al (A15), Nb{sub 2}Al ({sigma}), and NbAl{sub 3} (DO{sub 22}) have been calculated using the linear-muffin-tin-orbital (LMTO) method in the full potential (FP) approach. Relaxation and distortion effects have been included and have been shown to play an important role in the stabilization of the DO{sub 22} intermetallic phase. In order to get the interaction parameters to describe the energetics of the bcc and fcc solid solutions, FP-LMTO calculations have been performed for various superstructures based on the bcc and fcc lattices. To discuss thermodynamic properties and the phase diagram of the Al-Nb system, the cluster variation method configurational entropy has been introduced using the tetrahedron-octahedron approximation in the fcc solid solution and the tetrahedron approximation in the bcc solid solution. The thermodynamic data obtained in this work agree fairly well with the available experimental data. Connections with Calphad approaches are also discussed. An attempt to calculate composition-temperature phase diagram of the Al-Nb system is presented, using a semiempirical treatment of the liquid phase. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 531820
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 56, Issue 2; Other Information: PBD: Jul 1997
- Country of Publication:
- United States
- Language:
- English
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