| Aluminum alloys and high-strength steels are widely used in aerospace,rail transportation,automobile and shipbuilding industries due to their respective high specific strengths and low density.In particular,aluminum/steel composite connection joints,while ensuring the structural performance and greatly reducing their own weight,are of great significance for the realization of lightweight vehicles.However,due to the difference in thermophysical properties between two metals,intermetallic compounds are easily generated at the interface when dissimilar metals are welded,causing welding difficulties,which limits their further popularization in industrial production.In this paper,in view of the welding difficulties of aluminum/steel dissimilar metals,6060 aluminum alloy and DP980 high-strength steel are used as welding materials.The laser-arc composite heat source welding experiment of aluminum/steel dissimilar metals was carried out using the structure of lap joints with steel on top and aluminum on bottom.First,the process parameter range and welding joint forming rule of direct overlap welding of aluminum alloy and high-strength steel were explored.In order to improve the mechanical properties of the welded joint,Ni foil is used as an interlayer added between the aluminum/steel lap surface.It is expected that the generation of intermetallic compounds at the interface is reduced by physical blocking and metallurgical reactions.In addition,in order to further improve the joint performance,a composite intermediate layer is used by Ti O2 powder to the weld,and finally an adhesive is applied to the area of the weld overlap surface to form a laser-arc-glue integrated molding structure,to investigate the effects of the composite interlayer and the adhesive on the mechanical properties,microstructure and element distribution of the joint.The research results show that the laser-arc composite heat source is used to perform direct lap welding experiments on aluminum/steel dissimilar metals.Welding joints with well surface formation can be obtained.As the laser power increases,the weld penetration also increases,and the joint mechanics performance tends to increase first and then decrease.A thick Al-Fe intermetallic compound layer is generated at the joint interface,and there are many defects in the welded joint.The maximum joint shear tensile load is 128 N/mm,and the joint fails at the aluminum / steel interface intermetallic compound layer.After the Ni interlayer was added,the maximum tensile shear load of the joint was significantly increased to 173 N/mm,which was 35% higher than that without the Ni interlayer.Analysis of the joint morphology and element distribution found that the addition of the Ni interlayer effectivelysuppressed the interdiffusion of Al and Fe elements,and the intermetallic compound layer thickness was controlled within 10 μm.From the distribution of Ni elements,part of the Ni atoms are dissolved in the Fe matrix to form Fe(Ni)solid solution,and part of the Ni atoms diffuse into the Al matrix with Fe atoms to form Al-Fe-Ni ternary compounds.The aluminum/steel laser-arc-glued integrated welded joint with composite intermediate layer was analyzed for mechanical properties,microstructure and element distribution.The aluminum/steel laser-arc-glued integrated welded joint with composite interlayer was analyzed for mechanical properties,microstructure and element distribution.The research found that the mechanical bonding force of the glue joint and the welding metallurgical bonding force can greatly improve the mechanical properties of the joint.The structure of the joint with the composite interlayer was analyzed.The joint morphology and interface element distribution were similar to those of the Ni interlayer.There were no obvious defects such as crack inclusions.The Ti element was dispersedly distributed at the Al-Fe interface to form the dispersion strengthening.The maximum tensile shear load of the joint is187 N/mm. |
PDF Full Text Request