ZrO2/Ni nanocomposite was produced via pulse electrodeposition using a nickel sulfmate bath. The effects of main factors including pH value,temperature T,current density Dk and ZrO2 content ρ on t he electrodeposit were dealt with by the Taguchi method. Experimental results show that the current density and ZrO2 content affect the electrodepositing process significantly. Nanocomposite with an average grain size o f about 50 nm and ZrO2 content of up to 0.4 wt% was produced under the optimal condition. The Young’s modulus of the achieved composite is similar to that of polycrystalline Ni. The microhardness is much higher than that of common pure Ni,primarily due to the ultrafine grains of Ni matrix by the Hall-Petch mechanism. The homogeneous dispersion of stiff ZrO2 particles in the Ni matrix acting as dislocation pinning and microcrack pinning also results in the strengthening effect.
ZrO2/Ni nanocomposite was produced by pulse electrodeposition and its superplastic properties were investigated by the tensile and bulging tests. The as-deposited nickel matrix has a narrow grain size distribution with a mean grain size of 45 nm. A maximum elongation of 605% was observed at 723 K and a strain rate of 1.67×10-3s-1 by tensile test. Superplastic bulging tests were subsequently performed using dies with diameters of 1 mm and 5 mm respectively based on the optimal superplastic forming temperature. The effects of forming temperature and gas pressure on bulging process were experimentally investigated. The results indicated that ZrO2/Ni nanocomposite samples can be readily bulged at 723 K with H/d value (defined as dome apex height over the die diameter) larger than 0.5, indicating that the nanocomposite has good bulging ability. SEM and TEM were used to examine the microstructure of the as-deposited and bulged samples. The observations showed that significant grain coarsening occurs during superplastic bulging, and the microstructure is found to depend on the forming temperature.
