Microscopic phase-field simulation for the effect of the fourth-nearest pair potentials on precipitation mechanism of Ni₇₅Al₅V₂₀ alloy

The effect of the fourth-nearest pair potentials on the precipitation mechanism of Ni₇₅Al₅V₂₀ alloy is studied using a microscopic phase-field kinetic equation. Our simulations demonstrate that both DO₂₂ phase and Ll₂ phase have a mixed precipitation mechanism of non-classical nucleation growth and spinodal decomposition without changing the fourth-nearest pair potentials. When the absolute value of the fourth-nearest pair potential between Ni and Al (namely V⁴_Ni-Al, negative) increases, the precipitation mechanism of Ll₂ phase becomes spinodal decomposition. And when the fourth-nearest pair potential between Ni and V (namely V⁴_Ni-V) increases, the precipitation mechanism of DO₂₂ phase is spinodal decomposition, the Ll₂ phase is non-classical nucleation and the Al concentration in Ll₂ phase gains. When the absolute value of the negative V⁴_Ni-V increases, the mechanism is similar to the increase of V⁴_Ni-V; when the positive V⁴_Ni-V increases, the mechanism is similar to the decrease of V⁴_Ni-V.