In order to solve the problem that the magnesium alloy is easy to soften the welded joint during welding, the magnesium alloy was handled by the cryogenic treatment at different temperatures, and the mechanical properties of the welded joint were improved by changing the microstructure of the substrate.Results showed that with the decrease of cryogenic treatment temperature, the number of dimples in the crystal increased, the grain size decreased, the number of particles in the second phase increased, the diffraction peak value of each phase increased, and the mechanical properties of the welded joint improved significantly.Among them, the mechanical properties of the magnesium alloy MIG welded joint after-190 ℃, 12 h cryogenic treatment were the best.Compared with the untreated welded joint, the hardness, tensile strength and elongation of the magnesium alloy MIG welded joint with best mechanical properties were increased by 48.83%, 8.02% and 1.25%, respectively.
