Tensile behavior of electrodeposited nanocrystalline Ni

In order to investigate the characteristic of nanocrystalline material during superplastic deformation, nanocrystalline nickel with the mean grain size 70 nm was produced by electrodeposition. Tensile tests at and above room temperature were carried out to investigate the mechanical properties of electrodeposited Ni. Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and Energy Disperse Spectroscopy (EDS) were employed to examine the microstructures of the as-deposited and deformed specimens. The results at room temperature showed that nanocrystalline Ni had limited elongation but high tensile strength up to 1000 MPa. A maximum elongation of 380% was observed at 450°C and a strain rate of 1.67 × 10^-3 s^-1, which proved the low temperature super-plasticity for nanocrystalline Ni. Grain growth and grain elongation were observed in the deformed specimen. The fracture surface appeared intergranular crack, due to the oxide formed during tensile test.