Nanocrystalline pure nickel (nc-Ni) was produced by pulse electrodeposition and its
superplastic properties at and above room temperature were investigated. The electrodeposited nickel
has a narrow grain size distribution with a mean grain size of 70nm. Uniaxial tensile tests at room
temperature showed that nc-Ni has a limited plasticity but high tensile strength up to 1GPa at strain
rates between 10-5 and 10-2s-1. However, when the temperature increased to 420 and higher, test
specimens showed uniform deformation and the elongation value was larger than 200%. A maximum
elongation value of 380% was observed at 450°C and a strain rate of 1.67x10-3s-1, SEM and TEM
were used to examine the microstructures of the as-deposited and deformed specimens. The results
indicated that fracture was caused by intergranular cracking and most cracks were originated from the
brittle oxide formed during the tensile test. Grain coarsening was observed in the deformed specimen.
The role of temperature and strain on grain growth was evaluated by comparing the microstructure of
deformed samples with that of samples statically annealed. Deformation mechanism was discussed
based upon the deformed microstructure and strain rate jump tests.
The corrosion performance of decorative electrodeposited nickel chromium coating. The role of sulfur.
