Analysis on welding characteristics of ultrasonic assisted laser welding of AZ31B magnesium alloy

To the problems of welding porosity and poor weld formability in the laser welding process of magnesium (Mg) alloy, the experimental research of ultrasonic assisted laser welding of AZ31B Mg alloy was carried out, and its welding characteristics and the effect of ultrasonic vibration on microstructure and mechanical property of weld joint were analyzed. The results indicate that, the cavitation and acoustic streaming of ultrasonic vibration on weld pool can significantly improve weld defect and microstructure morphologies. With ultrasonic assisted laser welding technology, the weld appearance becomes smooth and sound. The weld porosity declines from 4.3% to 0.9% and its average size decreases. The width of columnar grain zone near fusion line decreases and the equiaxed grains in fusion center zone increase tremendously, the refining effect on the grain is obvious. Also, the mechanical properties of welds can be significantly improved, the tensile strength and elongation can be increased to 87% and 64% of the base metal.