Theoretical and experimental study of the γ and γ′ equilibrium in the Ni–Al–Cr–Co system

Several alloys of the Ni–Al–Cr–Co system with constant Ni content of 70 at.% were studied after long term annealing at 1000 °C by means of analytical electron microscopy in the concentration interval relevant to the γ and γ′ phase field existence. The co-existence of γ and γ′ phases, their compositions and phase ratios were compared with theoretical data obtained by means of the software ‘Thermo-Calc’ designed for modelling of phase equilibria in multicomponent systems. The necessary thermodynamic database was constructed on the base of information available for lower order systems. This approach is well established and it has been successfully applied in our previous study of similar quaternary alloys annealed at 900 °C. The new results show good agreement of theory with experiment and confirm that the developed thermodynamic database is suitable for theoretical description of γ and γ′ equilibrium in the Ni–Al–Cr–Co system.