Microscopic phase-field simulation of the γ′(Ni₃Al) phase separation process

The separation process of γ′(Ni₃Al) phase in Ni-Al alloy containing 12.5at. %Al was simulated at the atomic scale using the microscopic phase-field model and microclasticity theory. The simulation results show that γ′ phases firstly are formed from the disordered solid solution by the mechanism of non-classical nuclcation growth, resulting in the appearance of single ordered domain separated by the antiphase domain boundaries (APBs). With the ordered domains isostrcutural decomposing and the Al-lcan regions disordering spontaneously, the equilibrium state is formed finally. In the whole stage of precipitation, the shape of γ′ phase becomes more regular and their orientation becomes more obvious, at the later stage, γ′ phase presents quadrate shape with round corner and align along the [10] and [01] directions.