Thermodynamic reassessment of the Ni–Si–Ti system using a four-sublattice model for ordered/disordered fcc phases supported by first-principles calculations

Abstract

A thermodynamic reassessment of the ternary Ni–Si–Ti system was performed by means of CALPHAD (CALculation of PHAse Diagram) method. The fcc_A1/Ni3Si-L12 disordered/ordered transition was described using a four-sublattice model. The enthalpies of formation of the ternary compounds τ1, τ2, and τ4 and end-members of the Ti5Si3 and Ni3Ti phases at 0 K in the Ni–Si–Ti ternary system were computed via first-principles calculations to supply necessary thermodynamic data for the CALPHAD modeling. In the Ni–Si–Ti ternary system, it was clarified that the ordered Ni3Si-L12 phase is formed from the liquid phase with the addition of Ti. An optimal set of thermodynamic parameters for the Ni–Si–Ti system was obtained by taking into consideration of the experimental data from the literature and theoretic values from the present first-principles calculations. Comparisons between the calculated and measured phase diagrams indicated that almost all the reliable experimental information was satisfactorily accounted for by the present modeling.