Theoretical and experimental study of the influence of Cr on the γ+γ′ phase field boundary in the Ni–Al–Cr system

The Ni–Al–Cr system, as a relatively simple yet sufficiently representative model system for commercial Ni-based superalloys, has been studied in the γ+γ′ two-phase field. The phase boundaries and chemical composition of γ and γ′ phases were calculated by means of the software Thermo-Calc applying both the general compound energy model (J. Alloys Comp. 247 (1997) 20) and the compound energy model with constraints to bond energy for the γ′ phase (Intermetallics 6 (1998) 487). Values obtained are compared with experimental values for four alloys with Cr contents in the range 0–15 at.% after long-term annealing at 900 °C. The experimental determination of chemical composition of existing phases was performed by means of energy-dispersive X-ray analysis in a scanning transmission microscope. The comparison shows acceptable agreement between calculated and experimental data.