Microscopic Phase-field Simulation for the Influence of Aging Process on the Precipitation Process of Ni75Al15Ti10 Alloy

The precipitation process of Ni₇₅Al₁₅Ti₁₀ alloy was simulated by a microscopic phase-field kinetics model. The microscopic morphology evolution was studied, which indicates that the precipitation process can be divided into two stages: the first is the transformation from L1₀ phase to L1₂ phase, and the second is the formation of the stoichiometric L1₂ phase. The effect of single aging temperature on the microstructure, atomic occupation probability and atomic diffusion was investigated. The result shows that the shape of γ′ precipitates transforms from irregular shape to regular cuboid and the degree of orientation growth increases with increasing aging temperature. But the higher the aging temperature, the lower the occupation probability and the order degree. Meanwhile, the path of diffusion of Al atom is from the interface of the γ′ phase to the internal, and the diffusion of Ti atom is the opposite. Furthermore, we studied the dual aging to improve occupation probability of γ′ precipitates and to discuss their influence on the γ′ phase. Dual aging can not only obtain a stable γ′ phase with regular shape, but also increase the occupation probability of Al and Ti and inhibit the formation of anti-site defects.