Effect of temperature on the evolution of diffusivity, microstructure and hardness of nanocrystalline nickel films electrodeposited at low temperatures

Most nickel (Ni) films galvanostatically electrodeposited at 40–50 °C exhibited low hardness about 4 GPa and rough surface. In this article, we have investigated Ni electrodeposition at low temperatures of 5–20 °C in order to enhance the hardness and smoothness of films and performed by potentiostatic mode instead of galvanostatic mode to avoid the low-temperature precipitation of electrolyte agents. Effect of temperature on the evolution of diffusion coefficient, deposition rate, morphology and hardness was studied. Electrodeposition at low temperature without hard-element addition can reduce diffusion rate and produce the fine-grain, smooth morphology and dense film together with compressive residual stress to enhance hardness up to 6.18 GPa at 5 °C. The growth and hardening mechanism of low-temperature electrodeposited Ni were further discussed in details.