Technology Of Filling Clearance And Optimizing The Bonds During Ultrasonic Brazing

In this dissertation, the process of filling clearance induced by ultrasonic, the behavior of the oxide film removal and the technologies of improving the strength of the joints have been studied, during ultrasonic brazing for aluminum alloy and aluminum matrix composites. The velocities of filling the clearance and the behavior of oxide film removal are investigated, and Marc software is used to analyze the influence factors. The mechanical properties are improved by optimizing the bonds of 2024Al and the particles reinforced aluminum matrix composites SiCp/A356.The Results show that the velocity of filling clearance for aluminum matrix composites is faster than that for aluminum alloy. The greater is the input amplitude, the greater is the output amplitude, and the faster is the velocity of filling clearance for the same kind of base material. While the input amplitudes are same for different base materials, the output amplitudes are different due to different Young's modulus, so the velocities of filling clearance are also different. The Young's modulus of the aluminum composites is higher, the output amplitude is higher, and the velocity of filling clearance is faster. The oxide film can be removed completely after filling clearance of the brazing alloy induced by ultrasonic. The shortest time of oxide film removal for aluminum alloy is shorter than that of aluminum matrix composites. The wider is the width of the clearance, the longer is the shortest time of oxide film removal.The strength of the joints can be improved while applying the optimizing technologies after aluminum alloy are joined by the brazing technology of filling clearance. The percent of eutectic in the bond decreases, while the weigt percent of Al in the bond increases and the weigt percent of Zn decreases, by raising the temperature and holding on the temperatures to promote the diffusion between the base metal and the bond. When the liquid alloy in the bond is squeezed out to improve properties of the bonds, the highest shear strength of bonds for aluminum alloy 2024Al is 193MPa. For aluminum matrix composites SiCp/A356, the bonds of aluminum alloy are also optimizd by the technology, so particles reinforced bond for aluminum matrix composites SiCp/A356 are fabricated and the strenngh of the bond can also be enhanced.