During annealing at around 800K, Ni could quickly penetrate into Cu due to diffusion-induced recrystallization. To examine this penetration rate, the kinetics of diffusion-induced recrystallization in the Cu(Ni) system was experimentally determined here. Experiments were conducted using polycrystalline Cu/Ni/Cu diffusion couples which were prepared by using a diffusion bonding technique. The diffusion couples were isothermally annealed at 723 to 823K for times of up to 144h. During annealing, a region alloyed with Ni was formed in Cu from the Cu/Ni interface due to diffusion-induced recrystallization. The concentration of Ni on the Ni-rich side in the diffusion-induced recrystallization region remained almost constant independent of the annealing time, but gradually increased with increasing annealing temperature. However, the mean thickness of the diffusion-induced recrystallization region increased with increasing annealing time. The growth rate of the diffusion-induced recrystallization region was a monotonically increasing function of the annealing temperature. The experimental findings of the kinetics study were quantitatively analyzed using a mathematical model. The analysis indicated that the growth of the diffusion-induced recrystallization region was controlled by the interface reaction at the moving boundary of the diffusion-induced recrystallization region as well as the boundary diffusion along the grain boundaries across the diffusion-induced recrystallization region.

Kinetics of Diffusion-Induced Recrystallization in the Cu(Ni) System at Low Temperatures. Y.Yamamoto, M.Kajihara: Journal of Electronic Materials, 2008, 37[11], 1710-20