Properties of nanocrystalline iron–nickel alloys fabricated by galvano-static electrodeposition

Iron–nickel nanocrystalline alloys were electrodeposited onto a carbon steel substrate from a simple chloride bath with different Ni/Fe ion ratios. A solid solution of bcc structure with high percentage of Fe was deposited from baths with low Ni/Fe ion ratio. By increasing the Ni/Fe ion ratio in the electrolyte to 4, a dual phase alloy consisting of bcc and fcc crystal structures was formed. Further increase in Ni/Fe ion ratio resulted in the formation of a single phase with fcc crystal structure. The average grain size of Fe–Ni alloys was about 8–16 nm which was increased with the decrease of Fe content of the alloy. EIS measurements showed medium frequency capacitive and low frequency inductive loops indicating that Fe–Ni electrodeposition is diffusion controlled process and adsorption of electrochemical active species occurs which inhibits grain growth and results in nanocrystalline structure. The effect of pulse current density was to produce lower grain size which resulted in higher hardness.