Primary study of laser-MIG hybrid welding for MB8 magnesium alloy

Laser-MIG hybrid welding for MB8 magnesium alloy with 10 mm thickness was carried out and the process stability, appearance of weld, microstructure and tensile strength were studied.The results demonstrate laser-MIG hybrid welding is an effective welding method for MB8 magnesium alloy.By the laser-arc interaction, the stabilities of MIG arc burning and droplet transfer are improved during hybrid welding and the obtained weld is full and even.Under the used welding parameters, hybrid welding increases the welding speed by 125 % in comparison of single laser welding.Because of the disappearance of surface pit defect, the tensile strength of hybrid weld is far higher than that of laser weld and reaches 87.2% of substrate.For the hybrid weld, the microstructure in the center of fusion zone is equiaxed grain but that nearby fusion line is columnar grain.Owing to relatively slow solidification speed, the wide upper part has obvious coarser grain size than the narrow lower part.