Pore suppression study on Mg/Al joint in laser welding by dual magnetic fields and ultrasound wave

To reduce porosity in laser welding of Mg/Al dissimilar metals, a new method of laser welding assisted by Ultrasonic Waves and Dual Magnetic Fields(Alternating Magnetic Field and Stable Magnetic Field) is proposed. By observing the flow of the molten pool through a high-speed camera, comparing the number and size of bubbles during laser welding assisted by different external energy fields, the influence of Stable Magnetic Fields and Alternating Magnetic Fields on the solidification rate of the welding pool is studied respectively.SEM and OM were adopted to analyze the microstructure and the tensile properties were tested. The results show that applying Alternating Magnetic Fields and Ultrasonic Waves in the laser irradiation area can accelerate the fluidity of the molten pool and break up coarse grains. Adding a Stable Magnetic Field can reduce the cooling rate of the molten pool and prolong the bubble escape time. The porosity defects can be effectively suppressed and the grain size can be refined, through the combined action of two magnetic fields and Ultrasonic Waves.