Dual-beam Laser Welding Of 1420 Aluminum-Lithium Alloy

Today, laser welding is being used in industry due to high welding speed, small welding seam and narrow heat affected zone. In comparison to steel, Al alloys show a more complex influence of material properties on laser welding process which is mainly due to their lower absorptivity and higher thermal conductivity. In connection with other properties it often leads to defects- hydrogen pores, process pore and melt ejections. It was reported that the use of dual laser beam for welding could increase keyhole stability, make a better weld quality. So dual-beam laser welding is becoming an important research and development direction in the field of laser processing .The characteristics of the dual beam laser welding and the technics of Al-Li alloy laser welding by dual-beam are studied systematically in this paper. Firstly, the laser welding of steel was performed to explore the peculiarities with the dual beam mode in the experiment. The results show that the welding process is stable, the weld appearance is regular and the cross-section looks good with focal distance in range of 0~1.0mm when the beam's angle with 22°each other. The welding depth would decrease when the focal distance becomes lager than 1.0mm.General speaking, in the laser welding of aluminum alloys, the tendency of pores and blowholes in the types of 5083 and 1420 is bigger than that of others. So secondly, they were chosen as the test materials in the experiments for further investigation. It is found that, for aluminum alloy of 5083, the weld quality with stable welding process, low pore rate and small pore dimension can be achieved with the dual-beam laser welding at the focal distance of 0.4mm between the beams. The results of dual-beam laser welding for 1420 Al-Li alloy on the way of scanning on the plate show that low porosity was made by optimum parameters without preweld treatment. Finally, the 1420 Al-Li alloy butt-welding experiments were carried out with different technics. Optical microscope and scanning electron microscope were used to analyse the microstructure and the qualities of the welding joint. The influence of mechanical properties of the weld joints was investigated too. The data of tensile test show that the average value of the tensile strength for welding joints is 336.1Mpa, about 87.5﹪as much as that of the base metal, in butt welding mode with proper technics.