For the bigger diffusion coefficient of the nickel other than that of the copper, the nickel layer would diffused into the copper layer, leading to the forming of Cu-Ni solid solution.

• 在扩散过程中，由于镍的扩散系数比铜大，镍层扩散进入铜形成了铜镍固溶体，界面呈现单向迁移。