Experimental investigation and thermodynamic calculation of phase equilibria in the ternary Fe-Si-Ta system

Abstract

Two isothermal sections of the Fe-Si-Ta ternary system at 1100 °C and 900 °C in the whole composition range have been experimentally determined combined with EPMA and XRD techniques. Except for these known ternary G, E, and V phases, a new ternary compound named X was detected with the composition region about 27.1–29.9 at% Fe, 30.6–31.7 at% Ta and 39.5–41.2 at% Si. Si has an extensive solubility in the Fe2Ta phase, and the solubility of Fe in the Ta2Si phase tends to be parallel to the Fe-Si side. Based on the experimental results in this work, the Fe-Si-Ta ternary system has been assessed using the CALPHAD method. A set of reliable thermodynamic parameters for the Fe-Si-Ta system was obtained. The current thermodynamic description is in good agreement with available experimental data. The calculated liquidus projection and invariant reaction scheme in the Fe-Si-Ta ternary system were presented. The present work can provide essential experimental and thermodynamic data for the establishment of the G-phase strengthen alloy database.