Effect of Ultrasonic Vibration Assistance on Microstructure Evolution and Mechanical Properties in Laser-Welded AZ31B Magnesium Alloy

Given the susceptibility to weld porosity and poor weld formability in laser beam welding (LBW), this study delves into an examination of the impact of ultrasonic vibrations on microstructural morphologies and mechanical properties in AZ31B magnesium (Mg) alloy. A comparative analysis was conducted between ultrasonic vibration-assisted LBW and conventional LBW. The results established that the effective elimination of weld porosity, an outcome attributed to the combined effects of cavitation and acoustic streaming, resulted in a weld characterized by a visually seamless and structurally robust appearance. Furthermore, the incorporation of ultrasonic vibration assistance in the welding process yielded a finer microstructure as compared to the conventional LBW. Moreover, the lamellar structures of beta-Mg17Al12 were transformed into particles and evenly distributed throughout the alpha-Mg matrix. In addition, the incorporation of 50% ultrasonic vibration assistance yielded notable improvements in tensile strength (259.6 MPa) and elongation (11.1%). These values represented enhancements of 4.8% and 35.4% as compared to joints fabricated by using conventional LBW.