Thermodynamic modeling of the Hf–Ti–Si ternary system

A thermodynamic description of the Hf–Ti–Si system was developed using the phenomenological or Calphad approach, based on the critically assessed binary thermodynamic descriptions and experimental data of ternary phase equilibria. The parameters of all ternary phases were optimized using experimentally measured solid-state phase equilibria at 1350 °C, melting temperatures of selected alloys, and primary solidification information for metal-rich Hf–Ti–Si alloys. Comparisons between the calculated results and the experimental measurements show that the present modeling can satisfactorily describe the experimental information for the metal-rich region of the Hf–Ti–Si ternary phase diagram for Si concentrations of up to 40 at%. The experimentally identified transition reaction L + Hf(Ti)2Si → (Hf,Ti)5Si3 + β(Hf,Ti,Si) at the metal-rich end of the ternary phase diagram is confirmed by this calculation.