Thermodynamic modeling of the Al-Co-W, Al-Ni-Ta and Co-Ni-W ternary systems

Thermodynamic descriptions of the Al-Co-W, Al-Ni-Ta and Co-Ni-W ternary systems are the foundation for developing thermodynamic database and material design for the Ni-based alloys. In the present work, the Al-Co-W, Al-Ni-Ta and Co-Ni-W systems were optimized based on the reliable experimental data by means of the CALPHAD method. The liquid, & gamma; (Fcc_A1) and & beta; (Bcc_A2) phases were described as substitutional solution model, and the & gamma;' (Fcc_L12), B2 (Bcc_B2), & mu; (Co7W6) and Ni3Ta phases were described with sublattice models. The Co3W phase was treated as a stoichiometric compound due to the limited homogeneity range in the Al-Co-W system and described as (Co, Ni)3W in the Co-Ni-W system. The self-consistent thermodynamic parameters for the Al-Co-W, Al-Ni-Ta and Co-Ni-W systems were obtained. Comprehensive comparisons between the calcu-lated results and measured phase equilibrium data show that most experimental information is satisfactorily accounted for by the present thermodynamic description.