Interdiffusion in Cu‐Ni, Co‐Ni, and Co‐Cu

Quantitative results are obtained for the temperature and concentration dependence of the inter‐diffusion coefficient in Cu–Ni couples. An activation energy of 23.5 kcal/mol is calculated for the interdiffusion at medium concentrations in the temperature range 700 to 1000 °C. Micro‐radiographic investigations clearly show that grain boundary diffusion is the dominant mechanism. Diffusion couples of Co–Ni and Co–Cu are also studied by the aid of X‐ray micro‐radiography. Here too grain boundary diffusion is evidently the essential mechanism at lower temperatures, but volume diffusion apparently occurs at an earlier stage than in the Cu–Ni system.