Preparation Of Nanocrystalline Nickel Foil And Study On Forming Properties And Process Of Solid Granules Medium

The grain size of nanocrystalline metal materials is usually at the nanometer level.Therefore,compared with traditional materials,the smaller grain size makes nanocrystalline metal materials have great advantages in thermal,mechanical and electrical properties.At present,the main forming method of nanocrystalline metal materials is high-temperature superplastic forming.The material can obtain a large amount of deformation at high temperature,but with the increase of temperature,the internal grains of the material are easy to grow up,which not only loses the original excellent performance,but also limits the application field of the material.In order to solve the above problems,solid granules medium forming process was adopted in this paper to carry out the forming experiment on the deposited nanocrystal nickel foil,and N4 rolling nickel foil was used as the comparative material for verification,so as to study the forming performance of this process method.In this paper,the deposited nanocrystalline nickel foil was prepared by pulsed electrodeposition method.Unidirectional tensile experiments were carried out on the deposited nickel foil and N4 rolled nickel foil.The tensile pieces were observed and analyzed by SEM and TEM.The results show that both materials have relatively large strain at low strain rate,and the deposited nickel foil has good plasticity at low temperature,while the rolled nickel foil has large strain at high temperature.The deformation activation energies of the two materials were calculated,and the deformation mechanism was analyzed with TEM images.The constitutive equations of the two kinds of materials were established,and the forming numerical simulation of the solid granules medium of the deposited nickel foil was carried out by using the finite element analysis software MSC.MARC.The results show that with the decrease of temperature and pressure rate,the height of the forming part increases gradually,and the thickness of the forming part is more uniform when the slow pressure rate is adopted.Different from the traditional bulging,the part with the largest wall thickness reduction rate appears at the round corner of the die.The forming die of solid granules medium with diameter of 5 mm was designed.The experiment was carried out at different temperature and pressure rate and the quality of the forming part was analyzed.The results show that the best forming temperature of the deposited nickel foil is 250 ?,and the deformation at the corner of the die is large,and the equivalent strain is higher than the true strain of the material.Therefore,it can be considered that this process gives better play to the plasticity of the material.The best forming temperature of rolled nickel foil is 350 ?.Combined with TEM image,it can be seen that this process method has good forming properties for materials with different microstructure.