Research On Brazing Technology And Mechanism Of Aluminium Metal Matrix Composites Reinforced With SiC Particulates

Particulate reinforced aluminum metal matrix composites, which exhibit high specific strength, specific stiffness, higher wearability, dimensional thermal stability, have wide application prospects in aerospace, aviation structure, electron, medicine, and thus represent the mainstream of contemporary research and development of metal matrix composites. However, the special microstructure of aluminum matrix composites, which lead to the poor weldability and the difficulty in obtaining high strength welded joint, severely hinder the application of the composites. Compared with other welding technique, brazing has many advantages in joining Al-MMCs. So in this paper the brazing mechanism of SiCp/101Al composites was systematically investigated by using argon protect furnace brazing and vacuum brazing. Effects of parameters (temperature, holding time, pressure) of brazing of Al-MMCs on the joint shear strength have been studied. The microstructure, composition, phase of joint region, and the microstructure and composition of fracture have been analyzed using the equipment of optical microscope, SEM, XRD, TEM.This paper put forward that the joint strength increased with the growing of the brazing temperature and the holding time, and reached the maximum, strength decreased, however, when the temperature and holding time continuously increased. From the microstructure we can see that the filler metal fusion and diffusion to the matrix metal, and take the eutectic reaction. The element Si and Cu of the filler metal diffuse to the matrix Al, Si phrase nucleates and grows based on the surfaces of heterogeneous SiC particles due to their similar crystal structures. As a result, Si phase plays a role as a connection medium in between SiC and Al phase. In this way, the connection strength is enhanced locally and the interfacial bond quality of Al/SiC composites is improved. From the XRD analysis of the joint, Al-Cu,Al-Si and SiC phase were detected, it proved that the SiC from the base material was diffused to the brazing joint and increased the shear strength of the joint. The SEM pictures show that many of the fracture were ductile fracture, so it proved the argon protect furnace brazing and vacuum brazing is feasible to joint SiCp/101Al composites.