Thermodynamic modeling of the Ta-Mo-C ternary system

The Ta-Mo-C system was assessed by means of the CALPHAD approach. All of the phase diagram and thermodynamic information available from the literature were critically reviewed. The liquid was modeled as substitutional solution phase, while the carbides including fcc-(Mo,Ta)C1-x, bcc-(Mo,Ta), hcp-(Mo,Ta)2C and η-MoC were described by using corresponding sublattice models. The ζ-Ta4C3-x was considered as a linear compound with carbon content fixed, while shp-MoC was treated to be a binary stoichiometric phase. There was no ternary compound reported in this system. The modeling of Ta-Mo-C ternary system covers the entire composition and temperature ranges, and a set of self-consistent thermodynamic parameters for the Ta-Mo-C system was systematically optimized. Comprehensive comparisons between the calculated and reported phase diagram and thermodynamic data show that the reliable information is satisfactorily accounted for by the present modeling. The liquidus projection and reaction scheme of the Ta-Mo-C system were also generated by using the present thermodynamic parameters.