Brazing Process And Bonding Mechanism Of SiC_p/6063Al Composites Joint Brazed Using Al-Si-Cu-Y Filler Metal

SiCp/Al composites have characteristics of small density, high strength, high stiffness ratio, low coefficient of thermal expansion, etc. In the electronic packaging areas have extensive application prospects. However, due to the constraints of connectivity, SiCp/Al composites will be restricted. Brazing is applied to joining of SiCp/Al composites because of lower heating temperature, smaller effect on the reinforcement, less welding deformation, and so on. While lack of proper filler metals is the main problem for brazing of SiCp/Al composites.In this paper, the contents of elements in the filler metal were adjusted and the components were optimized based on the Al-Si-Cu filler metals. Effects of the contents of Si, Cu, Y on the microstructure, melting characteristics, wetting properties and toughness have been systematically investigated respectively. The Al-Si-Cu-Y filler metals which were suitable for vacuum brazing of SiCp/6063Al composites and SiCp/6063Al composites after nickel plating were developed, and suitable brazing process was designed. DSC was used to investigate the melting temperature of the filler metals. The microstructure of the filler metals, the brazing welding joints and the shear fractures were observed by using metallographic observation, SEM, EDS and XRD. The wettingability and toughness were measured through wetting properties test and toughness measurement, respectively. The results are summarized as follows:The temperature range of liquid-solid phase of Al-8.5Si-25Cu filler metal is the narrowest, and its wetting property is the best among eight groups of filler metals. Its toughness is not high, but is able to be processed into foil tape. Adding rare earth Y has little effect on the melting temperature of Al-8.5Si-25Cu filler metal. The wetting property and toughness of Al-8.5Si-25Cu filler metal increase first and then decrease with the increasing addition of Y The wetting property of Al-8.5Si-25Cu-0.3Y filler metal is the best. It can be processed into foil tape easily.Under the same brazing process, the shear strength of brazed joint with Al-8.5Si-25Cu-0.3Y filler metal is the largest. When the content of Y is 0% and 0.5%, the shear strength of brazed joint is lower, an excess addition of Y may deteriorate joint quality. When the content of Y is 0.3%, it can significantly reduce the size of the primary Si, change the morphology of Si, refine the a(Al) and improve the distribution of 0 (Al2Cu) in the brazing seam.Using Al-8.5Si-25Cu-0.3Y as brazing filler metal, the shear strength of brazed joint of SiCp/6063Al composites increase first and then decrease with the improvement of brazing temperature and the prolonging of holding time. When brazing at 560℃ for 10min, the shear strength reaches the maximum 135.32MPa. When brazing at 550℃ for 30min, the shear strength of brazed joint for SiCp/6063Al composites after nickel plating reaches the maximum 121.34MPa. Continue to improve the brazing temperature and holding time, the thickness of metal compound layer increases and the shear strength drops sharply.When brazing at 560℃ for 10min, the fracture paths of brazed joints of SiCp/6063Al composites vary in different contents of Y in filler metals. When the content of Y is 0%and 0.5%, the fracture modes of joints are brittle fracture. When the content of Y is 0.5%, long-flake rare earth compounds exist in fracture. When the content of Y is 0.3%, the fracture mode of joint is ductile-brittle mixed fracture. When brazing at 550℃ for 30min, brittle fracture surface occurs around the IMC layer. The fracture path is influenced by the size and morphology of Si. When the content of Y is 0.5%, there are a lot of long-flake rare earth compounds which distribute in the fracture.