Analysis of Diffusion-controlled Phenomena at the Interface of α/γ Diffusion Couples of Stainless Steels

The interdiffusion of Ni, Cr, and Mo across the interface in the diffusion couples of type444/type316L stainless steels was simulated using the DICTRA software. The distance of interface migration and the Ni diffusion distance into the ferrite phase were calculated and compared with the experimental results previously reported by a present author. The calculated results agree very well with the experimental results. An analytical model based on the analytical solutions for the semi-infinite solute diffusion equations has been proposed. In the model, all solute elements are considered and diffusion paths are calculated. The supersaturations of the solutes defined both for the ferrite phase and the austenite phase are calculated from the calculated diffusion paths. According to the model it is shown that the temperature dependency of the interface migration distance and the Ni diffusion distance can be quantitatively evaluated by the supersaturation for Ni.