Thermodynamic calculation of the phase diagram of the Co-Nb-Ta system

A thermodynamic description of the ternary system Co-Nb-Ta is obtained by combining the descriptions of the lower-order systems according to the CALPHAD method. The thermodynamic data set for the binary Co-Nb system is taken from an earlier paper (1998), where a new thermodynamic model for the μ-phase was introduced. The μ-phase appears in several transition metal systems, including Co-Ta. The model is applied to the Co-Ta system and extended to the ternary Co-Nb-Ta system. The thermodynamic descriptions of the systems Co-Ta, Nb-Ta and Co-Nb-Ta are reported in the present work. (orig.)