A physico-chemical approach in binary solid-state interdiffusion

A physico-chemical approach is developed, which can be used in binary diffusion couples to determine diffusion parameters of product phases with a wide homogeneity range, as well as phases with a narrow homogeneity range. It is demonstrated that this approach is basically equivalent to the diffusion-based treatment. However, the physico-chemical approach pedagogically sheds light on the chemical reactions occurring during interdiffusion at the interphase interfaces. This theory can be used in any binary system for any end-member condition to explain single-phase or multiphase diffusion-controlled growth. Ni–Al and Ag–Zn systems are considered here to calculate diffusion parameters following the physico-chemical approach. It is evident from our theoretical analysis and experimental evidence that in the case of presence of a stable Kirkendall marker plane one should expect the presence of duplex grain morphology in a particular phase layer.