Thermodynamic re-assessment of the Ti–Al–Nb system

Abstract

A CALPHAD based re-assessment of the thermodynamic description of the Ti – Al – Nb system was performed to take into account experimental evidence of the extension of the primary crystallization of the -phase to higher Al contents. The adjustable parameters of the analytic expressions of the Gibbs free energy for the Liquid, β-, β₀-, δ-, σ-, γ-, α-, and ₂-phases were re-optimized using available experimental data from a critical assessment of the literature. The calculated primary crystallization of -phase is in better agreement with experiment although the extension of the single phase -field to higher Al compositions could not be calculated. Calculated isothermal sections are in good agreement with experiment in the temperature range 1923 K to 1273 K.