Phase Field Modeling of Interdiffusion Microstructure in Ni-Cr-Al Diffusion Couples

Abstract

Evolution of interdiffusion microstructures was examined in ternary Ni-Cr-Al solid-tosolid diffusion couples using two-dimensional (2D) phase field simulation. Utilizing Cahn-Hilliard and Allen-Cahn equations, multiphase diffusion couples containing of fcc-γ and B2-β solid solution phases were simulated with alloys of different compositions and phase contents. Chemical mobility as a function of composition with constant gradient energy coefficients was used in the simulation. Simulated microstructures in γ+β/γ and γ+β/γ+β diffusion couples were compared with the experimental microstructures reported in literature. As observed experimentally, the model predicted the recession of γ+β region in the γ+β/γ couple and a stationary interface in γ+β/γ+β couple. Concentration profiles developed across the diffusion couples demonstrated that the interdiffusion occurs in the γ phase as well as in the γ+β region. Formation of single-phase γ and β layers near the interface of γ+β/γ+β couples was also investigated using the volume fraction profile obtained from the simulated microstructure.