Bending deformation and indentation hardness of electrochemically deposited nanocrystalline nickel-iron alloys

Abstract

Abstract Nanocrystalline nickel-iron microstructures, manufactured by means of an electrochemical deposition process via electrolyte solutions, were investigated to collect relevant information for the use of nickel-iron for micro-components. By varying the current density, nickel-iron coatings can be set to show specific grain sizes, iron content, lattice strains and textures. Uniform microstructures exist in each of the deposited nickel-iron coatings. The grain sizes determined using x-ray analysis (XRD) cover a range of 6 to 17 nm. XRD texture analyses parallel to the deposition plane resulted in {111} and {200} orientations. To characterize the material's mechanical properties indentation hardness measurements and micro-bending tests were performed. For a 0.01 %-offset bending yield strength (Rp0.01*), grain sizes of 6 to 17 nm clearly demonstrate Hall-Petch behavior. In addition, the investigations show lower work hardening and lower values for remaining edge strain at fracture for decreasing grain size. In contrast to Rp0.01*, the Young's modulus, indentation modulus, indentation hardness values and the bending strength, within their scatter bands, all remain largely unaffected by the different microstructures. Overall, all measured strength and hardness values of the considered nanocrystalline microstructures are very high in comparison to microcrystalline microstructures.