Study On Laser Welding Of Rare Earth Magnesium Alloy And Magnesium Alloy To Aluminum Alloy

With the increasing demand for lightweight in the field of industrial production,lightweight materials such as magnesium and aluminum have been more widely used.In the application of magnesium alloy and aluminum alloy,the connection between magnesium homologous materials and magnesium/aluminum dissimilar materials is inevitable.Welding is the most commonly used method for joining metal materials in industrial production,and reliable welding process is one of the key ways to further expand the application range of magnesium alloy and aluminum alloy.Therefore,it is of great significance to study the connection between magnesium homogenous materials and magnesium/aluminum heterostructures.Laser welding is a precision welding technology with high energy density.In this paper,laser welding is used to study the weldability of magnesium alloy.Firstly,laser welding of AZ31 magnesium alloy with rare earth Ce was carried out,the microstructure of the joint and its effect on mechanical properties were studied,and the influence mechanism of rare earth on the joint was analyzed in depth.The joint was heat treated,and the microstructure changes of the joint before and after heat treatment were compared and analyzed.Secondly,laser lap welding was used to weld AZ80magnesium alloy and 6061 aluminum alloy with Ni interlayer.The effects of welding process parameters on joint forming,microstructure and mechanical properties were studied,and the evolution of microstructure and its influence on joint properties were analyzed in depth.The main conclusions of this paper are as follows:By laser welding of AZ31 magnesium alloy with rare earth element Ce,the microstructure of the weld is fine dendrite,and there is no obvious heat affected zone in the joint.The dispersed granular second phase and a small amount of continuous Mg₁₇Al₁₂,acicular Al₁₁Ce₃,rod and irregular block Al₁₀Ce₂Mn₇ phase are formed in the weld.After the solid solution treatment of the joint,all the Mg₁₇Al₁₂ phase in the joint is dissolved in theα-Mg matrix,and some of the undissolved Al₁₁Ce₃ and Al₁₀Ce₂Mn₇ phases are dispersed in the weld,which plays a role in dispersion strengthening of the weld.The maximum tension and shear force of the joint is 126 N,and the fracture occurs at the interface between acicular Al₁₁Ce₃ andα-Mg matrix.Laser welding of AZ80 magnesium alloy with nickel interlayer and 6061aluminum alloy was carried out.The welding speed is 30 mm/s,the defocus is-1 mm,and the laser power is 1000 W to 1300 W.With the increase of laser power,the weld width increases slightly and the penetration depth increases obviously.The magnesium-rich and aluminum-rich weld zone is formed in the joint,the microstructure distribution of mg-rich weld zone is relatively uniform,the granular Al Ni phase is dispersed in the weld,and there is no continuous brittle intermetallic compound layer at the weld interface;the microstructure distribution of aluminum-rich weld zone is uneven,and the morphology of Al Ni phase changes with the increase of laser power,and more brittle intermetallic compounds are formed in this area,which is the weak area of the joint.When the laser power is 1100 W,the granular Al Ni phase formed in the aluminum-rich weld zone strengthens the joint,and the mechanical properties of the joint are the best,and the maximum tensile and shear force is 584.46 N.