Research On Techology And Mechanism Of Al-Mg Dissimilar Metals' Welding

The welding of Al-Mg dissimilar metal can realize the advantages of Al alloy and Mg alloy.Getting both Al Alloy's easy processing and corrosion performance and Mg alloy's lightweight and shock absorption.It will have great potential applications in the fields of automobile manufacturing,shipbuilding,aerospace and national defense.So the welding of Al and Mg is an urgent problem to be solved in the application development.This paper carries out research on the technology and mechanism of 6061 Al Alloy and AZ31B Mg alloy welding,and then explore the characteristics of molding process and mechanical properties of Al-Mg welding,trying to obtain welding joint quality factors and mechanism of effect of Al-Mg welding.The research of 6061 Al Alloy and AZ31B Mg alloy welding process is mainly divided into four parts:The first is the 6061 Al Alloy and AZ31B Mg alloy direct welding.The second is 6061 Al Alloy and AZ31B Mg alloy with a gap and the welding torch is on the side of aluminum offset.The third is joint 6061 Aluminum Alloy and AZ31B magnesium alloy with annealing heat treatment.The forth is 6061 Aluminum Alloy and AZ31B magnesium alloy welding with the over layer of Zn.Firstly,the direct welding of 3mm thick 6061 Al Alloy and AZ31B Mg alloy is mainly to find the appropriate process parameters for the follow-up test,when the welding current is 65-70A,we can get the effective welding joint.Then,the welding research is keeping gap in Al-Mg and offsetting the welding torch on the side of Al.By adjusting the welding position,when the welding current is 66A,the appearance of the welded joint is better.On the basis of previous experimental study,the Al-Mg welding joints are annealed in different temperature.When the annealing temperature is 350 degrees Celsius,the performance of the welded joint is significantly improved,the tensile strength is improved,and the hardness is decreased.Finally,when taking Zn into the middle of Al-Mg,the tensile strength is further improved and the performance is further improved.Through different analysis ways like metallographic observation,mechanical test,SEM,EDS and XRD,we found that the main reasons that affect the quality of welded joints is Al₃Mg₂ and Al₁₂Mg₁₇ intermetallic compounds,Thermal stress and columnar crystal has a negative effect on welded joints.Through the gap and the welding torch offsetting Al side can reduce heat output to control the production of intermetallic compounds,annealing can reduce the thermal stress and columnar crystal,the Zn can inhibit Al₃Mg₂ and Al₁₂Mg₁₇ intermetallic compounds.