Microscopic phase-field simulation of precipitation process and atomic site occupation of γ′ phase in Ni ₇₅Al ₁₅Mn ₁₀ alloy

Based on the microscopic phase-field kinetic model and the microelasticity theory, the precipitation process and the atomic site occupation of γ′ phase of Ni ₇₅Al ₁₅Mn ₁₀ alloy were simulated. The results indicate that when the alloy is aged at 1273 K, L1 ₀ phase is formed firstly, and then gradually transformed into L1 ₂ phase with the development of the long range order parameter at the initial precipitation stage. Atomic ordering precedes compositional clustering, and γ′ phase precipitation is of the congruent ordering + spinodal mechanism. The volume of γ′ ordered phase is less than that of γ phase, and the volume ratio of the ordered to the disordered is about 60%. The β site is mostly occupied by Al atoms (the corner site of γ′ phase), while the α _II and α _I sites are mostly occupied by Mn atoms; moreover, the occupation probability at α _II site is higher than that of α _I site, Mn atoms mostly occupies the site of Ni atoms, and the precipitated γ′ phase is a kind of (Ni, Mn) ₃Al phase.