We compare the experimental and computed results of the stress assisted interdiffusion. The Cu-Fe-Ni diffusion couples were investigated at 1273 K. The alloys in this system do not form ideal solid solutions and consequently the Calphad method was used to compute the elements activities. The method applied in this work base on the Darken’s drift velocity concept, Vegard law and Navier-Lamé equation. It allows computing the deformation field during the interdiffusion process. The driving force for diffusion in such a ternary system is the gradient of the chemical potential which can be calculated from the concentration profiles and using the known thermodynamical data of the system. Comparison between the Darken method without stress and the influence of stress on the interdiffusion in the Cu-Fe-Ni system is presented. Simulations that take into account the deformation field give better fit to the experimental results. Moreover we show qualitative and quantitative differences between the simulations of interdiffusion using the Calphad method and with the ideality sweeping statement.