Abstract: An Mg-Al-Zn-Er filler metal is developed. During the melting of filler metal, ultrasonic vibration is applied to the liquid metal. The power of ultrasonic is 600 W, the frequency of ultrasonic is 20 kHz, and the ultrasonic vibration time is 0-240 seconds. The liquid filler metal is casting under 600 ℃. The experiment results show that the melting points of developed filler metal do not exceed 355 ℃ and the melting range is not beyond 10 ℃, which benefit for the soldering. The ultrasonic vibration acting on the melting filler metal has the effect of purifying microstructure, refining the grain and accelerating the precipitation of α-Mg and Al3Er. During the soldering of AZ31 magnesium alloy, the Al3Er precipitation phase act as nucleation site, preventing the coarsening of crystal grain. When the ultrasonic vibration time of solder is approaching 180 s, the shear strength of lapping joint is 59.7 MPa, which is almost one point two times that of the filler metal which has not undergo ultrasonic treatment.

Key words: Mg-Zn-Al- Er filler metals;ultrasonic;grain refine;soldering