Study On Room And High Temperature Properties Of Cu/WC_P Layered Functionally Graded Materials

With the development of ultra-high-voltage(UHV) transmission network in our country towards to the large capacity and high pressure, particulate reinforced metal-based conductive ceramic composite materials can't meet the requirement, especially in the field of high-voltage circuit break contact materials. Temperature rise caused by contact resistance and current distribution from the surface to the body in electrical contact materials are nonhomogeneous, easily lead to fusion welding and arc erosion. If the composition of the electrical contact materials is designed to nonhomogeneous from the surface to the body, different gradient distribution of electrical contact materials can be designed based on the specific application requirements, optimizing the electrical and mechanical properties. But the preparation of this totally gradient distribution of electrical contact materials have great difficulties, actually layered functionally graded materials is often used to take the place of the fully gradient materials. Because of the designability and the heterogeneity, we must carry out further research on the mechanical and electrical behavior of layered functionally graded. This paper studied the layered Cu/WCP functionally graded materials. Using a combination of macroscopic properties and microstructure observation, the room and high temperature mechanical and fracture behavior of Cu/WCP layered functionally graded materials has been studied.Firstly, using vacuum hot pressing technology, Cu/WCP composites and layered Cu/WCP functionally graded materials have been prepared. The effect of volume fraction and size of WC particle have been investigated. Secondly, the high temperature performance of layered Cu/WCP functionally graded materials has been studied. The effect of temperature on the mechanical properties of Cu/WCP composites have been compared. Lastly, to understanding the deformation and fracture of the Cu/WCP layered functionally graded materials, tensile and three-point bending test have been conducted. The microstructure of the layered Cu/WCP functionally graded materials was characterized by scanning electron microscopy to reveal the microscopic mechanism of damage failure.The experimental results were as follows: (1) Cu/WCp composites with higher content particles have better mechanical strength, but worse ductility. Cu/WCp composites show high dependence of paticle size, Cu/WCp composites with smaller particles have higher strength and ductility.(2) Cu/WCp composite is temperature-sensitive. With increasing temperature, the strength of the Cu/WCp composite decreased. There has a critical temperature that grain boundary which not slip in room temperature have been slipped. The ductility and strength of Cu/WCp composite significantly decreased.(3) The tensile properties of layered Cu/WCp functionally graded materials is different from isotropic composites. Compatibility of deformation lead to stress redistribution, The higher WC content have, the larger stress experience. Fracture occurs in high WC content layer first, and then extend to the low WC content layer. In addition, the Cu/WCp functionally graded materials have interlaminar stress between layers, but the delamination not happen in large scale, only have partial cracking and delamination.(4) The high temperature bending experiment has been carry out at the Cu/WCp layered functionally graded materials which force direction parallel to gradient direction, analyzing the effect of temperature on the carrying capacity, deriving of the bending stress in the linear elastic range. Fracture experiments of the Cu/WCp layered functionally graded materials with through crack under bending load have been conducted. The results show that high WC content side of the Cu/WCp layered functionally graded materials, crack propagation distance was significantly higher than the low WC content side at the same time.