Effect of Welding Speed in High Speed Laser-TIG Welding of Magnesium Alloy

In order to investigate the effect of welding speed on microstructures and mechanical properties in high speed welding, low power laser-tungsten inert gas (laser-TIG) hybrid welding process is proposed on AZ61 magnesium alloy. Defect-free welds are produced by employing welding speed ranging from 2,000 mm/min to 6,000 mm/min. It is found that welding speed has a significant influence on microstructures and mechanical properties of the joints. Results indicate that with rapid increasing of welding speed, both the liner energy and average grain size decrease on the premise that fully-penetrated joints with no macroscopic porosities or cracks are obtained. The microhardness in the weld fusion zone increases with the welding speed. It is also found that the tensile strength decreases after an increase with the increase in welding speed. The fracture mode changes from mixture fracture of ductile and brittle to typical intergranular fracture feature.