Experimental Investigation and Thermodynamic Assessment of Phase Equilibria in the Al-Ta-V Ternary System

Abstract

The phase equilibria in the Al-Ta-V ternary system at 1000 °C and 1200 °C have been studied by using electron probe microanalysis and X-ray diffraction. τ-Al2.9Ta2.7V1.4 phase was found in the Al-Ta-V ternary system in both two isothermal sections. The addition of V makes the Al69Ta39 phase be stable at 1000 °C. The linear compound Al3(V,Ta) phase (D022-type) forms a continuous solution from the Al-V side to the Al-Ta side at both temperatures. Based on our experimental results, reported liquidus projection of the ternary Al-Ta-V system and thermodynamic data of the binary systems of Al-V, Al-Ta and V-Ta, a thermodynamic evaluation of Al-Ta-V system was carried out by CALPHAD technique. A set of reliable thermodynamic parameters for the Al-Ta-V system was obtained. The current calculation results agree well with the available experimental data. The invariant reaction scheme of Al-Ta-V ternary system was presented. The present study could provide essential experimental and thermodynamic data for establishing a comprehensive Co-based alloy database.

Keywords: Al-Ta-V ternary system, Phase diagram, Thermodynamic modeling, Microstructure