Synthesis of Bulk Nanocrystalline CoNi Alloys and Study of Their Microstructure and Magnetic Properties

Abstract

Bulk nanocrystalline materials (BCNMs) of cobalt-nickel alloys have been prepared by high-speed jet electrodeposition (JED). Furthermore, the influence of the concentration of additive in electrolyte on deposition rate, current efficiency, as well as the morphology, chemical composition, microstructure, and properties of CoNi alloys has been investigated. The experimental results show that the amount of the additive has little effect on the deposition rate, current efficiency and Co-content of the deposited alloys, but they have a remarkable effect on the microstructure and properties. As the concentration of additive increases from 0 to 2.5 g/l, the grain-size of deposition layer decreases from 14 nm to 5 nm, the microhardness increases from HV495 to HV675, and the soft magnetic properties of the deposition layers are sharply improved. However, when the amount of the additive is over 2.5 g/l, the influence of additive is significantly weaker. The results indicate that the JED method with additive in electrolyte is a very effective technique for the manufacture of the nanocrystalline CoNi alloy.

Keywords:

• Additive
• Cathodic polarization curves
• Coercivity
• CoNi alloy
• Electrodeposition
• Hydrometallurgy
• Microstructure
• Remanence