Research On Brazing Technology And Mechanism Of High-volume Ratio SiC_p/6063Al Composites By Low-melting Glass-ceramic Solder

High-volume ratio(more than 50 vol.%) silicon carbide particles reinforced aluminum matrix composites(Si Cp/Al) has high specific strength, low coefficient of thermal expansion and high dimensional stability. As a kind of ideal lightweight thermal-control and electronic packaging materials, high-volume Si Cp/Al composites have wide application prospects in aerospace and military area. The key to get the reliable brazed joint of high-volume SiCp/Al composites is to solve the problem of solder wetting. Based on high-volume Si Cp/Al composites’ ceramic surface, the paper proposes a method which brazes 60 vol.%Si Cp/6063 Al composites by low-melting glass-ceramic solder in the air. Taking advantage of the composites’ anodic oxidation, improvement of low-melting glass-ceramic solder’s wettability on composites’ surface can be obtained, which can help a lot to obtain brazed joints with good shape and high reliability.The DSC of low-melting glass-ceramic solder have been tested, which can help to determine the temperature range of the wetting and brazing test. By anodic oxidation, oxide film can grow on Si Cp/6063 Al composites’ surface. Wetting test shows that the presence of oxide film can promote the wettability of low-melting glass-ceramic solder on Si Cp/6063 Al composites. In addition, the wetting temperature and holding time can also promote wettability in a certain extent. When the wetting temperature is 450℃, holding time is 10 min, the wetting angle of low-melting glass-ceramic solder on anodized SiCp/6063 Al composites’ surface is 25°. When the temperature exceeds 450℃, pores with large diameter will appear in low-melting glass-ceramic solder.The brazing of anodized Si Cp/6063 Al by low-melting glass-ceramic solder paste was carried out in air. The interface has a dissolved diffusion layer, accompanied with little Al element diffusion. Pores with small diameter will be successfully removed by using low-melting glass-ceramic solder pieces. When the temperature is 450℃, holding time is 30 min, the shear strength of the brazed joints is 33 MPa, which is the maximum. While the brazing temperature and holding time increase, the shear strength of brazed joints shows a decline after a rising trend. The diameter of pores in low-melting glass-ceramic solder becomes larger and the dissolved diffusion layer becomes thicker, are the reasons of this phenomenon.