Microstructure and phase equilibria in the Ni–Al–W system

Several experimental alloys of the Ni–Al–W ternary system were prepared and their equilibrium microstructures were studied after long term annealing at temperatures 1173, 1273 and 1373 K by means of scanning and transmission electron microscopies with energy-dispersive X-ray microanalysis. Thermodynamic modelling based on CALPHAD approach was performed using software package Thermo-Calc and commercial thermodynamic database for Ni-based superalloys. Experimental results were compared with calculated data and a necessity of modification of selected thermodynamic parameters was stated. Optimization of ternary parameters for thermodynamic description of γ′ phase and binary parameters for intermetallic phases was performed using software package Thermo-Calc. The thermodynamic optimization based on newly obtained experimental results and experimental data available from literature resulted in good agreement of prediction with experiment.