Preparation Of Go-Ni Composites And Study On The Micro-Superplastic-Gas-Expansion Properties

The grain size of nanocrystalline metal materials is very small,which is usually in the range of several nanometers to tens of nanometers.Therefore,the grain boundary atoms have a large proportion and nanocrystalline metal materials show different physical,chemical and mechanical properties from those of ordinary metal materials.It is a very important research object in the field of material science nowadays.In recent years,it has attracted much attention from scholars all over the world.Plastic machining is one of the main methods to prepare micro parts in the process of nanocrystalline metal materials,which is widely used in the fields of micro electronics,micro electromechanical systems.However,the plasticity of nanocrystalline metal foil is poor compared with the traditional coarse grain metal materials,which makes the forming cost of nanocrystalline metal material too high and greatly limits the application and popularization.In order to solve the above problems,the Go-Ni composites were prepared by pulse electrodeposition method by adding Go solution into the electrodeposition solution,and the microforming properties of Go-Ni composites were studied by high-temperature superplastic micro-bulging forming experiments.The materials prepared by pulse electrodeposition have the advantages of uniform composition,low porosity and high density.Therefore,Go-Ni composites were prepared by pulse electrodeposition in this paper.The Go-Ni composite material having a Go content of 0.02 g/L,0.04 g/L,0.06 g/L,0.08 g/L and 0.1 g/L were prepared by adding Go solution to the electrodeposition bath.X-ray diffraction experiments were carried out on the prepared nanocrystalline Go-Ni composites.The diffraction pattern analysis shows that when the Go content is 0.06 g/L,0.08 g/L,and 0.1 g/L,the grain preferential growth of the composite foil resulted in texture and lattice distortion occured during electrodeposition.Tensile tests were carried out to study the mechanical properties of the composites at room temperature and the tensile fracture was observed by scanning electron microscopy.The results show that with the introduction of Go and the increas of the content,the strength of nanocrystalline Go-Ni composites increases gradually and the plasticity decreases.A high-temperature superplastic micro-bulging forming die with a diameter of 1 mm was designed.The effects of different process parameters(such as bulging temperature and pressurization rate)on the micro-bulging properties of Go-Ni composites with different Go contents were studied.The quality of bulging parts were analyzed.The experimental results show that the optimum micro-inflation forming temperature of composite foil is 300 ?.With the increase of Go content,the bulging height decreases gradually and the bulging height is higher when the pressure rate is faster.Combined with the results of X-ray diffraction analysis,the quality analysis of bulging parts shows that the introduction of Go makes the grains of the composite produce preferential orientation and texture and lattice distortion occured during electrodeposition,which results in the increase of strength and the decrease of plasticity of the composites.The bulging parts have some deviation compared with the hemispherical shape.