Microscopic phase-field simulation for the precipitation process of D0₂₂ and L1₂ phases in Ni-Cr-Al alloy

The precipitation processes of D0₂₂ and L1₂ phases in Ni₇₅Cr₁₉Al_6.0 alloy were simulated based on the microscopic phase-field kinetic model and the microelasticity theory in this paper. During early precipitation process, DO22 phases precipitated from the disorder matrix by the spinodal decomposition mechanism and the L1₂ phases precipitated by the non-classical nucleation growth mechanism, they both presented irregular shape, distributed randomly in the matrix. The elastic field produced by the lattice mismatch between the precipitates and the matrix has a strong influence on the late precipitation process. D0₂₂ and L1₂ phases showed anisotropic characteristic, and their precipitates presented cuboidal shape and distributed regularly along the elastic 'soft' directions ([100] and [001]), the highly preferential selected microstructure was formed during late precipitation process. The growth law was changed in the elastical strain system, there was no linear relationship between the cube of the average precipitate size and the ageing time as predicted by the classical Lifshitz-Slyozov-Wagner theory.