Initial precipitation and coarsening of the γ phase in inverse Ni–Al alloys

Abstract

Coalescence coarsening and Ostwald ripening as well as the kinetics of γ precipitation in the γ′ matrix of inverse Ni–Al alloys are investigated by phase field simulations. The ordering of the γ′ matrix during the initial phase transformation of inverse Ni–Al alloys is faster than clustering, and disordering of the γ precipitates is faster than dissolution. As the Al content increases from 20.2 to 20.8 at.% Al, the initial precipitation and growth of γ precipitates decelerates, and the volume fractions of γ precipitates decreases with higher Al content. The rate constants of steady-state coarsening decrease with decreasing volume fraction of γ precipitates, the particle size distributions (PSDs) are broader than the PSDs predicted by Lifshitz–Slyozov–Wagner theory at steady-state coarsening, and the PSD becomes broad with increasing volume fraction of γ precipitates. The simulated morphology and kinetics variation of the γ precipitates are similar to previous experimental results.