| Automotive lightweight is the current trend of automobile vehicles development.The use of light materials is the most effective way to achieve lightweight,and it will involve the steel/aluminum dissimilar metal connection.Laser welding has the advantages of high energy density,small heat affect zone and high degree of automation.There are big differences between steel and aluminum in physical and chemical properties,so it is easy to find pores and crack in the welding process,and it can also form Fe/Al intermetallic compound easily,thereby reducing the quality of the Fe/Al joint.Therefore,improving the Fe/Al welding defects and reducing the brittle compound are the technical problems that need to be solved in laser welding.In this paper,6061 aluminum alloy plate and DC51 D + AZ galvanized steel plate were selected as the research object.The alternating magnetic field assisted laser was added to the powder soldering test to study the effect of alternating magnetic field on forming the bead,mechanical properties of steel / aluminum joint,the fracture morphology and the intermetallic compounds.The main contents of this paper are as follows:(1)Theoretical aspects: The theory of adding the powder to the laser absorption rate during welding was explored.The process of adding the powder and the reason of adding the powder to improve the laser absorption rate were studied.The process of wetting and spreading of the brazing filler metal during the filling of the powder was carried out.Finally,the mechanism of the electromagnetic induction principle and the influence of the magnetic field on the welding performance of the joint is explained..(2)Related experiments: The laser welding experiment of 6061 aluminum alloy plate and DC51 D + AZ galvanized steel plate was carried out by fiber laser and the welding parameters were obtained and optimized by orthogonal experiment.Experiments on laser filling and soldering in different magnetic field strengths were carried out.The microhardness,tensile mechanical properties,fracture morphology and intermetallic compound of the welded joint were tested,and the morphology of the tensile fracture was analyzed.The results show that the alternating magnetic field can effectively improve the defects of the welding process.The electromagnetic stirringmakes the distribution of Fe,Al and Si in the molten pool uniform,and the microhardness and tensile strength were improved by more than 20%,and the intermetallic compound thickness was reduced,The plasticity of the joints was enhanced.(3)Fe/Al brittle compounds: The mechanism of Fe/Al compounds during welding was analyzed from the perspectives of thermodynamics and dynamics,and the formation process of different compounds was described.The effects of magnetic field on the kind and thickness of Fe/Al brittle intermetallic compounds were investigated.The effects of magnetic field and intermetallic compound on the properties of joints were analyzed by fracture morphology and tensile strength. |
PDF Full Text Request