Thermodynamic assessment within the Zr–B–C–O quaternary system

Thermodynamic modeling of Zr–B–C–O quaternary system is conducted within the CALPHAD framework by employing data obtained from first-principle calculations and literature. The lower order binary B–O is assessed in this work by estimating the thermodynamic properties of stable solid phases of B₂O₃ and B₆O and by estimating the gas and liquid phases. First-principle calculations, in conjunction with special quasirandom structure were used to predict enthalpies of mixing for the ternary solid-solution phase of FCC-Zr(C, O). The calculated results were used to optimize the model parameters pertaining to the cubic phase, which is described by a two-sublattice model. The modeled Zr–C–O ternary phase diagrams calculated at 1923 and 2273 K under ambient pressure and 4 Pa, respectively, are in agreement with experimental phase diagrams.