Thermodynamic assessment of the C-Zr-Nb ternary system

The whole C-Zr-Nb ternary system was assessed by means of CALPHAD method for the first time. All of the experimental phase diagram data available from the literature were critically reviewed and assessed using thermodynamic models for the Gibbs energies of individual phases. The solution phases including the liquid, fcc, hcp and bcc were described by the substitutional solution model. There is no ternary compound in this system. A set of self-consistent thermodynamic parameters for the C-Zr-Nb system is obtained. Comparisons between the calculated and measured diagrams show that the present thermodynamic description can account for the experimental information satisfactorily. The liquidus projection and reaction scheme for the C-Zr-Nb system were generated by using the present thermodynamic parameters. The effect of microstructure on the mechanical properties of C-Zr-Nb alloys homogenized at 1800 °C reported in the literature was discussed from a phase diagram point of view.