The system Ta–V–Si: Thermodynamic modeling

Abstract

Based on previously evaluated experimental data for two isothermal sections of the Ta–V–Si system at 1500°C and 1200°C, thermodynamic modeling of the ternary system has been performed. Ground state phase stabilities i.e., the energies of formation are reported for all nine binary compounds and for the τ1 ternary intermetallic using an ab initio density functional approach. The calculated energies of formation are in agreement with available experimental data and they were included in the thermodynamic modeling, which was performed within the CALPHAD approach using the Thermo-Calc software package and taking into account data from existing thermodynamic assessments of the binary sub-systems. The comparison of experimental with calculated data demanded a thermodynamic remodeling of the sub-systems Ta–V and V–Si. The resulting thermodynamic optimization yielded good agreement with the experimental results in the investigated temperature region.