Study On The Laser-TIG Hybrid Welding Of Dissimilar Magnesium Alloy And Steel With Ni As Interlayer

With the wider use of magnesium alloys,the problem of joining magnesium to steel was unavoidable to meet,especially in automotive industry,and so on.The joining of dissimilar metal magnesium and steel could bring their own good characters into play together,which was very expected.The technique development of joining magnesium to the other metals restricted the range of magnesium use and accelerated the use of magnesium.The progress in joining dissimilar will make more design program feasible and give the designer more choices. What's more,the study on the joining dissimilar metal magnesium and steel will make the flow in welding pool and element diffusion more obvious.As the most used welding method. laser-TIG hybrid welding of magnesium alloys and steel with successfully was meaningful definitely.Preliminary studies shown that the dissimilar magnesium alloy and steel were lap welded by Laser-TIG hybrid welding,the over-lapped weld joint between Mg alloy and steel could be obtained.But because of magnesium and steel do not mix in the liquid state,the magnesium was heavily oxidized.The shear strength was about 90 MPa,Metallic oxides were the main reason influenced the strength of weld.In order to enhance the mechanical property of Mg/Steel dissimilar joint,dissimilar AZ31B magnesium alloy and Q235 steel were weld by Laser-TIG hybrid welding with Ni as interlayer in this paper.The process characteristics and mechanism of Laser-TIG hybrid welding dissimilar metals were studied,and profoundly discussed the selection of welding parameters,the analysis of microstructures,distribution of elements,mechanical properties, welding defects,and so on.At the same time,describing the advantages of adding Ni foil by comparing with the Ni-free joint.The results showed that the dissimilar magnesium alloy and steel by Laser-TIG hybrid welding with Ni as interlayer could be obtained.The weld was good,and there were no significant weld defects.The stomata could be effectively prevented through the using of reasonable protective measures.The poor mierostructure of Ni-free joint was improved by adding Ni as interlayer.The Mg/steel dissimilar joints were joined more closely by adding Ni as interlayer,Fe and Ni were joined together in the form of solid solutions,while Mg alloy and Ni foil were joined together forming Mg₂Ni intermetallic compounds.With Ni foil as interlayer. the tensile strength of the joint was high compared with those without Ni foil.The strength was about 170MPa.