Ultrasonic vibration assisted tungsten inert gas welding of dissimilar magnesium alloys

The effects of ultrasonic vibration assisted (UVA) treatment on the microstructures and mechanical properties of MB3/AZ31 dissimilar magnesium (Mg) alloy joints were studied by microstructural characterization, micro-hardness testing and tensile testing. Results indicate that the welding pores are eliminated and coarse ￎﾱ-Mg grains of fusion zone are refined to 26 ￎﾼm, owing to the acoustic streaming effect and cavitation effect induced by the UVA treatment with an optimal ultrasonic power of 1.0 kW. In addition, Mg17Al12 precipitation phases are fine and uniformly distributed in the whole fusion zone of weldment. Micro-hardness of fusion zone of the Mg alloy joints increases to 53.5 HV after UVA process, and the maximum tensile strength with optimized UVA treatment increases to 263 MPa, which leads to fracture occurrence in the Mg alloy base plate. Eventually, it is experimentally demonstrated that robust MB3/AZ31 Mg alloy joints can be obtained by UVA process.