Research On Laser-MIG Hybrid Welding Process Of Magnesium Alloy Profiles

Magnesium is regarded as the green engineering material in twenty-first Century.In the same strength and rigidity condition,the weight of parts can be reduced by using magnesium alloy.In addition,magnesium alloy has good damping performance,good casting performance,good machinability,good heat dissipation,so magnesium has good application development prospect.The laser-MIG composite welding is an efficient hybrid welding method which applies the welding method to the welding of magnesium alloy.It is expected to obtain the welding joint with excellent welding quality and promote the application of magnesium alloy.In this study,laser-MIG hybrid welding process was used to weld the 5mm thick plates of AZ33 magnesium alloy.The welding process is stable,the weld bead is continuous,and the weld shape is beautiful.The influence of laser power,wire feeding speed and welding speed on weld size and shape was analyzed under different welding parameters.The welding wire with two different components,AZ33 and AZ63,was filled for butt welding,and the structure and mechanical properties of typical joints were studied.The weld is well formed and the maximum tensile strength can reach 220 MPa.The test results show that the weldability of magnesium alloy is poor,and its welding parameters are narrow when the laser-MIG hybrid welding is adopted.With the increase of laser power,the weld depth increases,and the laser power increases after the plate is welded,which mainly affects the weld width.The matching of different welding parameters has great influence on welding process and weld forming condition.When different welding wire were filled to the joints,the weld zone is composed of small equiaxial crystals.Near the fusion line,because the change of the temperature gradient,grain crystalline state change,columnar crystal appeared and growing towards the weld center.The welding joints have a narrow heat-affected zone(HAZ),grains in HAZ grew up because of the heat input.In the same welding joint,there is little difference in the hardness value of the weld zone,heart influence zone and parent material,and the average hardness of the weld zone is slightly higher than that of the parent material,and the hardness of the heat affected zone is slightly lower than that of the parent material.The hardness value of the joints is not very different when filling different wires.The tensile strength is slightly higher with filling AZ63 welding wire than that of filling AZ33.The weld zone is weakness zone in the weld joint,all tensile specimens are fractured in the weld zone after stretching,and the tensile fracture is brittle fracture.