Effect of ultrasonic field parameters on interfacial characteristics and mechanical properties of Mg alloy welding joint

In this research, high frequency ultrasonic vibration (UV) was firstly developed for the arc welding of MB3 Mg alloy in order to improve Mg alloy welding prone to porosity defects, coarse weld microstructure, and low joining strength problems. Authors investigated the influences of ultrasonic treatment on weld microstructures and mechanical properties of Mg alloy joints by introducing high frequency ultrasonic vibration into weld pool. Experimental results revealed that ultrasonic treatment encouraged equiaxed grain to form in the weld zone owing to the acoustic streaming effect and cavitation effect induced by ultrasonic treatment. Ultrasonic assisted Mg alloy joints with favorable mechanical properties were obtained through optimization of multiple experimental parameters. With the characteristic of plastic fracture, the tensile strength of the optimized butt joint reached to 239 MPa, which is equivalent to 93% of the tensile strength of the Mg alloy base metal. However, excessive ultrasonic power will destroy the stable solidification process of weld pool, resulting in the degradation of tensile strength.

Automated summary

High frequency ultrasonic vibration was used for arc welding of MB3 Mg alloy to improve welding defects and microstructure issues. By optimizing experimental parameters, Mg alloy joints with favorable mechanical properties were obtained. However, excessive ultrasonic power could degrade tensile strength.