Thermodynamic stability of doped FeAl-X (X = Pd, Ag, Pt and Ru) systems

Iron-aluminides based systems play a significant role in many industrial applications due to their excellent resistance to oxidation at high temperatures. In particular, these alloys are applicable as thermocouples. In this paper, we used first-principles density functional theory to investigate the stability of FeAl and ternary FeAl-X alloys. Their equilibrium lattice parameters are in better agreement to within 2% with the experimental data. We employed virtual crystal approximation and supercell approaches to model various atomic compositions at 0 ≤ x ≤1 for Ag, Pt, Pd and Ru. Their thermodynamic, electronic and mechanical properties were deduced from their equilibrium lattice constants. It was found that the addition of Ag, Pt, Pd and Ru enhances the stability at lower atomic percentage composition. It was found that Ag and Pd stabilizes the FeAl-X to lower percentage compositions. Furthermore, their heats of formation, density of states and elastic constants gave essential agreement to describe the structural, thermodynamic and mechanical stability of these systems.