Ab initio calculation of the BCC Fe-Al-Mo (Iron-Aluminum-Molybdenum) phase diagram: Implications for the nature of the tau(2) phase

The metastable phase diagram of the BCC-based ordering equilibria in the Fe-Al-Mo system has been calculated via a truncated cluster expansion, through the combination of Full-Potential-Linear augmented Plane Wave (FP-LAPW) electronic structure calculations and of Cluster Variation Method (CVM) thermodynamic calculations in the irregular tetrahedron approximation. Four isothermal sections at 1750 K, 2000 K, 2250 K and 2500 K are calculated and correlated with recently published experimental data on the system. The results confirm that the critical temperature for the order-disorder equilibrium between Fe(3)Al-D0(3) and FeAl-B2 is increased by Mo additions, while the critical temperature for the FeAl-B2/A2 equilibrium is kept approximately invariant with increasing Mo contents. The stabilization of the Al-rich A2 phase in equilibrium with overstoichiometric B2-(Fe,Mo)Al is also consistent with the attribution of the A2 structure to the tau(2) phase, stable at high temperatures in overstoichiometric B2-FeAl. (C) 2009 Elsevier Ltd. All rights reserved.

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Sao Paulo State Research Funding Agency (FAPESP, Sao Paulo-SP, Brazil)[2006/02470-0]

Brazilian National Research Council (CNPq, Brasilia-DF, Brazil)[301392/2004-8]

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Brazilian National Research Council (CNPq, Brasilia-DF, Brazil)[304038/2007-5]

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Coordena ao de Aperfeiqoamento de Pessoal de Nivel Superior(CAPES, Brasilia-DF, Brasil)