Evaluation of the thermodynamic properties and phase equilibria of the Re-Ta-W system

The phase equilibria and thermodynamic properties of the Re-Ta-W system are analyzed, and a complete thermodynamic description of the ternary system is obtained with the calculation of phase diagrams (CALPHAD) technique using a computerized optimization procedure. The thermodynamic modeling of intermetallic compounds σ and χ phases with three sublattices is discussed in terms of the effects of a large number of interaction parameters in the phases. The ternary parameters ΔGRe:Ta:W and ΔGRe:W:Ta of the σ and χ phases are assumed to be linear combinations of the binary parameters ΔGRe:Ta:Ta and ΔGRe:W:W of the σ and χ phases. The ternary-interaction parameters of the liquid and bcc phases are optimized using available experimental data. The calculated phase diagrams show good agreement with the experimental data.