Microstructure and Mechanical Properties of Ultrasonically Assisted Brazing of Dissimilar Cu–Al Alloys

An ultrasonic assisted brazing method, without flux and conducted in air, was developed to braze dissimilar copper-aluminum (Cu/Al) alloys. The microstructure and properties of Cu/Al joints of Sn–9Zn eutectic solder with different parameters were studied. The results show that the Intermetallic Compound (IMC) of the Sn–9Zn/Cu interface is mainly composed of Cu 5 Zn 8 and Cu 6 Sn 5 . According to first-principles calculations, the covalent bond formed by Cu and Zn atoms in Cu 5 Zn 8 is weak, whereas the covalent bond formed by Cu atoms and Sn atoms in Cu 6 Sn 5 is strong. In the absence of ultrasonically assisted brazing, the shear performance of the joint at 220 °C is 21.8 MPa. At the same temperature, the performance of the joint with the ultrasonically bonded 10 s is 36.8 MPa, which represents an average increase of 68% compared to the non-ultrasonic welding joints.