Effect of Some Operating Variables on the Characteristics of Electrodeposited Cu–Ni Alloys with and without α-Al2O3 and TiO2 Inert Particles

Abstract

A study was carried out on the electrodeposition of CuNi alloys containing inert (α-Al2O3 and TiO2) particles from a selected citrate bath. The cathodic polarization curves show that alloy deposition occurs at more noble potentials relative to either of the two parent metals and this indicated the formation of a solid solution. The addition of the inert particles into the selected bath led to a polarization-increasing effect and this increased with increases in the size and concentration of the particles in the bath. An explanation of the mechanism of codeposition of the inert particles with the alloy has been presented. On controlling the bath composition, CuNi alloys containing 11–40% of nickel could be deposited. The effect of the operating variables such as the concentration of the metal ions in the bath, pH and current density on the alloy composition indicated that the formation of the CuNi alloy belongs to the regular alloy deposition system. The current efficiency of the alloy deposition is relatively lower than for either of the two parent metals, from similar baths, and ranges between 76 and 84%. The microhardness of the deposited CuNi alloy improved from 170 to 248 kfg mm−2 as a result of codeposition of 1–2% of the inert particles. A direct correlation between the surface morphology of the deposited CuNi alloy, as revealed by SEM, and its microhardness could be detected. X-ray diffraction studies confirmed the dispersion of the α-Al2O3 and TiO2 phases in the CuNi alloy phase.