**Ultrasonic-Assisted Semi-Solid Forming Method and Microstructure Evolution of Aluminum**/**Copper Brazed Joints**

**Yin Liang 1,2, Jiruan Pan 3, Hua Zhang 2, Peng Huang 2, Jun Wang 1, Yuxin Shi <sup>1</sup> and Limin Chen 1,\***


Received: 31 December 2019; Accepted: 3 February 2020; Published: 6 February 2020

**Abstract:** Aluminum/Copper dissimilar metal connection devices have been widely used in equipment manufacturing. Ultrasonic vibration assisted semi-solid brazing technology is beneficial to improve brazing quality by using the good flow ability and strong deformation resistance of brazing alloy when it is in a semi-solid state. In this study, a new ultrasound-assisted high-frequency induction brazing method was used to braze aluminum and copper dissimilar metals under non-vacuum conditions with non-prefabrication of brazing filler metal. In a short time, uniform semi-solid brazed joint was obtained. Detailed investigations on the effects of aluminum-substrate side (Abbreviated as Al side) heat dissipation rate and ultrasonic vibration duration on the microstructure evolution and mechanical properties of semisolid weld were conducted. The results show that the welding seam obtained by the modification method increases the microstructure uniformity of brazing joint.

**Keywords:** ultrasonic vibration; dissimilar metal; semi-solid status; brazing; microstructure evolution
