Kinetics of diffusion-induced recrystallization in the Cu(Ni) system at low temperatures

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