Preparation Process By Electrodeposition And Forming Research With Assistant Current For Nanocrystalling Ni-Co Alloy

Nanocrystalline materials and superplasticity is a hot spot in the field of scientificresearch,while has been usd in the field of production wildly. Pulse electrodepositioncan produce nanocrystalline materials with small grain and high densify. This methodhas provided material base for the field of superplasticity. According to the constitutiveequation of superplastic, small grain in nanocrystalline materials may helps to realizelow-temperature superplastic. In this paper , we produce Ni-Co nanoalloy through theway of pulse electrodeposition and study the microstructure, mechanical properties,bending forming performance of Ni-Co nanoalloy. The superplastic formability undercomplex stress can be evaluated through the superplastic bulging tests.We research on the dosage of additive and preparation process in order to attrive theNi-Co nanoalloy with fine plastic. With the method of SEM and EDS, material surfacemorphology, microstructure, composition, hardness is analyzed. The material we hadproduced has small grain, comPact structure, high hardness. The quantity percentage ofCo and S is respectively 1.14% and 0.21%.Tensile tests are carried out to study the room temperature strength, hightemperature plasticity. Under the strain rate of 1.67×10^-3s^-1, the material has lowelongation of 8.8%, also has high breaking strength of 520MPa and tensile strength of580MPa at room temperature. Under the same strain rate, the material attrive highelongation of 269%. This phenomenon means that low-temperature superplasticity canbe obtained.V-shaped bending forming performance is studied through the methods of resistanceheating and furnace temperature heating. Forming temperature, holding time,lubrication can influence evaluation indexes. We discuss the significant sequencebetween them. The experimental results of two kinds of heating mode are similar.Under the same process Parameters, springback angle has little difference. The optimalprocessing Parameters is high temperature of 500℃, pressure-keeping time of 30seconds, non-lubricated.Superplastic bulging tests are studied through the methods of resistance heating andfurnace temperature heating. They can be used to evaluate the superplastic undercomplex stress. The maximum ratio of height and diameter is 0.6493 with the method ofresistance heating, while is 0.8416 with the method of furance heating. Fracturebehavior and microstructure was observed by the method of SEM. We analyzed the farcture behavior and impurity Particles coordination mechanism on superplastic. Afterforming, the nanograin grow up to microns grain. With the method of resistance heating,the grain size has big difference between each other and axial ratio is small. With themethod of furance heating, the grain size is uniform and axial ratio is big. Wallthickness of bulging Parts is nonuniform in the whole with two method of heating. ThePart which tightly comPacted is thick, which on the top is thin.