Thermodynamic description of the Ti–C–N–O system

A thermodynamic description for the Ti–C–N–O quaternary system was given by completing thermodynamic assessments for the constituent ternary systems. All ternary systems were combined into a single database that can be used to predict phase equilibria within the Ti–C–N–O quaternary system. The liquid phase was described using the Modified Quasichemical Model with a single sublattice. The δ-TiN phase was described as a solid solution using the Compound Energy Formalism (CEF) with two sublattices, each containing vacancies. The solubility of carbon in the ε-Ti2N phase was modeled using the CEF, where only Ti occupies the first sublattice, while C and N are placed on the second sublattice. The α-Ti and β-Ti phases were described by the CEF, where only Ti occupies the first sublattice, while C, N and O are placed on the second sublattice. A set of self-consistent model parameters was obtained and the available phase diagram and thermodynamic data were reproduced well.