Thermodynamic re-assessment of the Re-X (X=Al, Co, Cr, Ta) binary systems

Rhenium was one of important alloying elements in the Ni-based superalloys. Based on the molar Gibbs energy of the pure Re updated in SGTE Pure 5 database, the Re-X(X=Al, Co, Cr, Ta) systems were re-optimized by means of CALPHAD (CALculation of PHAse Diagrams) technique. In the present work, the phases liquid, fcc, bcc and hcp were described using a substitutional solution model. The phases AlRe, Al3Re, Al6Re, Al12Re, AlRe2 and Al11Re4 in the Re-Al system were described as stochiometric compound. The Al4Re_H and Al4Re_L instead of Al4Re were evaluated in the present work. The phases σ in the Re-Cr and Re-Ta systems and χ in the Re-Ta system were modeled as (X, Re)10(X, Re)20 (X=Cr or Ta) and Re24(Re, Ta)10(Re, Ta)24, respectively. A set of self-consistent thermodynamic parameters of the Re-X systems were obtained and the optimized results were in good agreement with the experimental data.