The Cu–Sn binary diffusion couples were annealed in the temperature range of 190 to 220°C. Diffusion coefficients in the η and ε phases as well as the Kirkendall effect were measured. Kirkendall markers moved toward the Sn side and consequently the movement suggests the preferential diffusion of Sn atoms by a vacancy mechanism.
The Cu–η, α–η and δ–η couples were annealed in the temperature range of 357 to 404°C. There was only one ε phase layer in each diffusion zone of the three types of couples. The ε phase in the δ–η couple grew at the highest rate in spite of the fact that it had the smallest diffusion coefficient. It may be concluded that the concentration gaps between the ε and its neighboring phases are most effective on the growth of the ε. From this point of view, it was possible to predict what phase layer should preferentially grow in the reaction diffusion of five binary systems.