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, γ (Fcc_A1) and β (Bcc_A2) phases were described as substitutional solution model, and the γ’ (Fcc_L12), B2 (Bcc_B2), μ (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 calculated results and measured phase equilibrium data show that most experimental information is satisfactorily accounted for by the present thermodynamic description.