Annealing behavior of nickel electrodeposited from sulfamate bath at different temperatures

Abstract

Nickel electrodeposits on copper plates were prepared from a sulfamate bath at a current density of 200 Am-2. The bath temperature was varied from 30 to 60°C at increments of 10°C. The recrystallization behavior was studied via the microstructural characterization of Ni deposits after 1 h of annealing at temperatures ranging from 200 to 600°C at increments of 100°C. In addition, optical metallography and cross-sectional transmission electron microscopy (TEM) were used to characterize the microstructure of Ni deposits. The texture of Ni deposit was determined by conventional X-ray diffraction method. Ni deposited at 50°C exhibited a weak [110] texture, whereas Ni plated at temperatures lower than 40°C displayed a strong [100] texture. The microstructural and hardness changes of Ni deposits upon annealing differed for the deposits with different textures. After annealing at temperatures higher than 300°C, the recrystallized nuclei were observed on the [110]-oriented deposits, which contained high-density dislocations and numerous twins. An equiaxed grain structure was observed for the Ni deposits annealed at 600°C. Conversely, for [100]-oriented deposits, which contained less lattice defects, the recovery and grain growth prevailed in the absence of pronounced recrystallization after 1 h of annealing at temperatures up to 600°C, when the [100]-oriented deposits still retained their well-defined columnar grain structure. The different annealing behaviors associated with the distinct textured Ni deposits could be explained by their different lattice defects. That is, the population density of twins associated with the as-deposited Ni markedly affected the feasibility of the formation of twin-free recrystallized nuclei.