Microstructural development of a nanocrystalline NiFe electrodeposit with banded structure

Abstract

Microstructural characterization of electrodeposited nanocrystalline NiFe was performed. Optical microscopy revealed a banded structure on the etched cross-section of the as-deposited material which was perpendicular to the growth direction (GD). Electron backscatter diffraction (EBSD) technique was used to investigate the microstructural development of the deposits upon isochronal annealing for 30 min in the range of 300-400°C. No preferential grain growth was observed and the banded structure was found to have no influence on the growth procedure. Inverse pole figures (IPFs) showed spread orientations for the grown grains after annealing at 300°C; which became more pronounced upon annealing and led to a sharp <111> texture parallel to the growth direction of the electrodeposition at 400°C. It was shown, both theoretically and experimentally, that the twining process can be responsible for the texture evolution. Microhardness measurements showed a stable profile throughout the cross-section. It was also observed that as the annealing temperature increases from 300 to 350°C the average hardness of the material decreases about 200 HV. In-situ compression test was performed on nanocrystalline Ni tubes and the corresponding deformation profile was studied.