Microstructure and phase equilibria in Ni–Al–Cr–Co alloys

Several alloys of Ni–Al–Cr–Co system with Ni content close to 60 at.% were prepared and annealed at 1273 and 1373 K with the aim to reach the state of thermodynamic equilibrium. The microstructure of quenched samples was studied by means of scanning and transmission electron microscopy. Phases equilibrated at high temperature were identified using selected area diffraction in transmission electron microscope. Energy dispersive X-ray analysis was used for evaluation of nominal alloy compositions as well as the chemical composition of individual phases. The results obtained experimentally are compared with the results of thermodynamic calculation using software ThermoCalc and a commercial database of thermodynamic data for Ni-based alloys. In most cases the results of calculation show good agreement with experiment. A few differences of the results obtained by the two approaches are pointed out and briefly discussed.