Effects of Cr content on compositional evolution and precipitation kinetics of γ′ phase in Ni–Al–Cr alloy: 2D phase-field simulation

The two-dimensional phase-field simulation coupled with the sublattice model is utilized to simulate the γ′ precipitation in Ni-12 Al-x Cr at.% (x = 8, 9, 10) alloys aged at 1073 K for 831 h. The compositional evolution of Cr and Al, and the precipitation kinetics of γ′ phase are studied. At the nucleation and growth stage, the concentration distribution of Cr and Al is characterized by an Al enrichment and Cr depletion at the γ/γ′ interface. As Cr content increases from 8 to 10 at.%, the partition ratio of Al and Ni into γ′ phase is promoted, and the equilibrium volume fraction of γ′ phase is increased, while the Al and Ni atoms at the corner site of L12-Ni3(Al, Cr) sublattice are replaced by Cr atoms partly. Besides, the coarsening rate constants of steady-state coarsening (166.2 < t < 831 h) are less than that of growth and coarsening stage (4.2 < t < 50.0 h), the increased Cr content promotes the coarsening of γ′ phase, and the average radius of γ′ phase obeys the time exponent 1/3 well for a high Cr content alloy.