Rapid Ultrasonic-Assisted Soldering of AZ31B Mg Alloy/6061 Al Alloy with Low-Melting-Point Sn–xZn Solders Without Flux in Air

Zhi-Wei Lai^1,2,3，Zhe-Yuan Huang^2,4，Chuan Pan³，Hui-Qiao Du⁵，Xiao-Guang Che²，Lei Liu²，Wei-Ming Long⁶，Gui-Sheng Zou²

1. School of Materials Science and Engineering, Tsinghua University2. Department of Mechanical Engineering, Tsinghua University3. China Iron & Steel Research Institute Group4. College of Materials Science and Engineering, Shanxi Key Laboratory of Advanced Magnesium-Based Materials,Taiyuan University of Technology5. Beijing Spacecraft Manufacturing Factory6. The State Key Laboratory of Advanced Brazing Filler Metals and Technology, Zhengzhou Research Institute of Mechanical Engineering

摘 要：A novel ultrasonic-assisted low-temperature soldering was developed to join AZ31B Mg alloy and 6061 Al alloy with a series of Sn–x Zn solders. The average maximum shear strength of the joints reaches up to 87.5 MPa at soldering temperature of 300 °C under ultrasonic assistance for only 5 s using Sn–20 Zn solder. The fracture path propagates completely in the soldering seam. The results indicate that the microjet generated by ultrasonic pressure in liquid solder could strike and splinter the Mg₂Sn intermetallic compounds into small pieces, which contributes to the enhancement of the joint strength. In addition, the primary Al（Zn） solid solution phase formed during cooling stage could also strengthen the joint due to the prevention of microcracks propagation.

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