The Experimental Research On Properties About Dissimilar Non-ferrous Metals Copper And Aluminum Of Brazing Process

The characteristics and industrial applications of copper and aluminium alloys were summerized in this paper, and the main problems in copper and aluminium welding were analyzed. Some welding methods that may be used on copper and aluminium alloys, and its procedure factors as well as its updated research results were reviewed, including cold welding, friction welding, diffusion welding, explosion welding, resistance pot welding, laser welding, brazing and so on, and the forwarding problems to be researched were pointed out as well.Regarding potential engineering application of Cu-Al dissimilar metal components as the background, copper and aluminium was connected by means of brazing and problems associated with brazing were studied. It was studied that joint properties in vacuum brazing by different parameters when using Al-Si-Mg filler metal, and choosing different brazing filler composition to study joint properties in the flame brazing. It was contained that the vacuum brazing and flame brazing experiments on dissimilar metals copper and aluminum, analyzing the microstructure, microhardness, mechanical property, area morphology in brazing zones and phase compositions of joints by means of optical microscope, Vickers, universal tensile testing machine, scanning electron microscopy and X-ray diffraction, and discussing the reasons that caused macroscopical and microcosmic defects, and the preventive measure measures in the brazing process of joints.The results show that good surface welded joints can be got under proper matching of brazing parameters. The main factors that affect the quality of the joints by the vacuum brazing are brazing temperature, holding time and the thickness of the brazing layer, while the factors that affect the quality of the joints by the flame brazing are the solder composition and assembling space. That the hardness of the central area on both sides of joints by the flame brazing is significantly higher than that of the proliferation zone further verify a large number of brittle phases coming in the brazing zones. The strength of joints by the vacuum brazing and diffusion welding is relatively low, while that of joints by the flame brazing is relatively high. The most tensile fracture of joints occurs in the central area of brazing, and that the fracture surface has the torn traces and a small part of the bright band can be inferred that the form of fracture can be the mixed ductile-brittle fracture morphology. The main phases in the brazing zones areα-Al solid solution, CuAl2, Al4Cu9 and so on, which will seriously undermine the strength of joints and lead to coming about micro-cracks in the weld. The common welded defects in the joints are brittle phases, porosity, cracks, etc. A small amount of rare earth elements in the filter metal can not only refine the grain, and disperse the brittle phase in the weld. The occurrence of weld porosity and cracks can be reduced by taking some measures, such as removing the oxide film, dirt and oil completely before welding, strengthening the protection for welding pool, etc.