Thermodynamic analysis of the Fe–Ti–P ternary system by incorporating first-principles calculations into the CALPHAD approach

A thermodynamic analysis of the Fe–Ti–P ternary system has been performed by combining first-principles calculations with the CALPHAD approach. Because of the lack of experimental information available, the enthalpies of formation of the Fe–P and Ti–P based binary phosphides were evaluated using the Full Potential Linearized Augmented Plane Wave method, and the estimated values were introduced into a CALPHAD-type thermodynamic analysis. Applying this procedure, the phase diagrams of the Fe–P and Ti–P binary systems, whose contents are uncertain so far, were calculated with a high degree of probability. The thermodynamic properties of orthorhombic anti- PbCl2-type FeTiP were obtained following the same procedure. The calculated phase diagrams were in good accordance with previous experimental results. The ternary phosphide, FeTiP, was in equilibrium with most of the phases in the ternary system, and was dominant in the liquidus surface projection.