Forming Properties At Elevated Temperature Of Ni Foil Electrodeposited

As an effective way to solve the poor ductility and the poor forming property ofnanocrystalline metals at room temperature, plastic forming at elevated temperaturehas become one of the most important forming methods of nanocrystalline metals.Among the methods for preparing nanocrystalline metals, the nanocrystalline metalsprepared by pulse electrodeposition get many advantages such as high density and lowporosity, so this method has been widely used in production. In this paper, nickel foilsthrough the way of pulse electrodeposition were produced then the mechanicalproperties and microstructure of the nickel foils were studied. The formability of thenickel foils by rigid punch forming and bulging forming at elevated temperature werealso studied.By changing the contents of saccharin, effect of saccharin density on grain sizeand plasticity of the nickel foils were investigated. And prepared five kinds nickel foils,the average grain sizes of these five kinds Ni foils are from974nm to33.2nm. With thehelp of tensile testing machine, SEM hardness tester, the mechanical property, surfacemorphology, microstructure and hardness were analyzed.Tensile tests were carried out to study the ductility of nanomaterials at roomtemperature, and the different mechanical properties between five kinds nickel foilswere analyzed. The elongation of the nickel foils with33.2nm average grain size isonly5.82%, and for the974nm average grain size nickel foil it can reach10.21%.Rigid punch micro-forming tests at elevated temperature were carried out at thetemperature of350℃~500℃and the punch displacement rate of0.03mm/min~0.5mm/min. The effects of the lubricant and the surface quality of the nickel foils inthe rigid punch micro-forming tests at elevated temperature were also analyzed. Weacquired the samples with the height of1.589mm and the diameter of1mm. Theheight-diameter ratio of these samples is1.589. The fracture and the surfacemorphology were analyzed by SEM, based on the microstructure observation, thefracture behavior and grain motion were discussed, and the effect processes ofdislocation and twin were also discussed.Bulging forming tests at elevated temperature were carried out with the furnacetemperature heating method. Selected three kinds female die diameters of1mm、3mm and5mm. And we acquired the samples with the height-diameter ratio of0.823. Thetest parameters like bulging temperature, bulging pressure, holding time andlubrication of the bulging forming tests at elevated temperature were also discussed.Contrast the forming property and the samples’ quality of the Ni folks made bypulse electrodeposition with two bulging rate at elevated temperature. The fracturecharacteristic and the motion features of crystalline grains and dislocations of the twoforming methods at elevated temperature were also analyzed by SEM.