Effect of Superimposed Sinusoidal a.c. on the Characteristics of Electrodeposited Ni,Cu and Cu-Ni Alloy Composites with α-Al2O3 and TiO2

Nickel, copper and copper-nickel alloy composites were electrodeposited without and with inclusions of inert α-Al₂O₃ and TiO₂ particles from closely similar selected baths. It was found that during electrodeposition a superimposed sinusoidal a.c. exerted a decrease in the cathodic polarization for the individual metals and the alloy composites. The higher the superimposed a.c. density and the lower its frequency the greater was the depolarizing effect. The combined effect of superimposed a.c. and inclusion of the inert particles in the bath on the cathodic polarization proved to be additive. Superimposed a.c. induced negligible changes in the cathodic current efficiency of nickel and copper metal composites deposition, whereas it caused a marked decrease (about 20%) in that of the copper-nickel alloy composites. The inert (α-Al₂O₃ and TiO₂) particles content in the individual metal and alloy composites as well as the alloy composition were influenced by the superimposed a.c. and correlated with its depolarizing effect. The above-mentioned changes exerted by superimposed a.c. controlled the growth morphology, as revealed by SEM, and the microhardness of the as-deposited metal and alloy composites. A correlation could be detected between superimposed a.c. and dispersion of α-Al₂O₃ or TiO₂ particles in an individual metal or alloy matrix, the grain refinement, and an improvement of its microhardness could be detected.