Thermodynamic modeling of the Nb–Hf–Si ternary system

Abstract

The thermodynamic descriptions of the Hf–Si and Nb–Si systems were modified based on the critically assessed experimental phase equilibria and thermodynamic properties. Using the CALPHAD (CALculation of PHAse Diagram) approach, a thermodynamic description of the Nb–Hf–Si system was developed from the Hf–Si and Nb–Si systems modified in the present study and the Nb–Hf system from the literature. The parameters of all ternary phases were optimized using the experimentally measured 1500 °C isothermal section and the liquidus projection at the metal-rich region of the Nb–Hf–Si system. Comparison between the calculated results and the experimental measurements shows that the present modeling can provide a satisfactory account of the experimental information for the metal-rich region of the Nb–Hf–Si ternary phase diagram. The thermodynamic description of Si-rich corner has been obtained principally by extrapolation due to lack of experimental data.