Phase-field simulation of re-dissolution of γ′ phase in Ni–Al alloy by continuous and second-order aging treatment

The morphology and kinetics evolution of the γ′(Ni₃Al) phase during re-dissolution are studied in Ni-15 at% Al alloy, the changes of volume fraction and average particle radius of the γ′ phase were clarified with phase-field simulation. During isothermal aging, the interdistance of the neighboring γ′ phase affects the interface concentration gradient of Al, which dominates the growth or re-dissolution of the γ′ phase particle. After isothermal aging at 700 K, the alloy is continuously heated to 900 K with different heating rates, the re-dissolution lag happens, meaning the coalescence coarsening of adjacent γ′ phase particles still proceeds at the initial heating stage. The pre-dissolution of γ′ phase with cubic shape is re-dissolved firstly at the edges and corners, in continuous heating to 900 K or by second-order aging from 700 to 900 K. Different from continuous heating, in the second-order aging process, the connected particles with band shape are broken initially by re-dissolving. At different heating rates, the similar dynamic relationships are abstracted for the volume fraction and the heating rates, and the average particle radius and the heating rates.