| 2A12 aluminum alloy and 7075 aluminum alloy is high-strength aluminum alloy which can be heat-treated.Aluminum alloy material has a low density and higher strength.These materials have become an ideal alternative to modern high-speed trains,cars and small cars.Laser-MIG hybrid welding focused on the advantages of laser welding and MIG welding.To aluminum alloy,it not only can improve welding efficiency and reduce defects,but also can improve microstructure and properties of welded joints.In this paper,temperature of welded joint,total deformation of welding plate,back wide,melting width and tracking point temperature and deformation are obtained by numerical simulation.Then,based on the total deformation of welding plate,the actual welding parameters were selected and actual welding was carried out.The back wide,melting width and total deformation of welded joint were verified by experimental data.The effects of laser power,welding current on formability and microstructure of welded joint were analyzed.The composition of phase in the welded joint was investigated by EDS and XRD.The effects of laser power and welding current on mechanical properties such as microhardness,tensile strength,elongation and impact toughness of welded joints were also analyzed.Choose a better overall performance of the welded joints,and the effect of aging treatment at 180?for 12 hours on microhardness and tensile strength of welded joint was analyzed.The conclusions are as follows:Numerical simulations show that:under the parameters of laser power 3.8KW,welding current 195 A welding,numerical simulation and the actual weld has a consistent weld width,back wide.In the total amount of welding deformation,the test of 2A12 aluminum side is better than that of 7075 aluminum side.Overall,numerical simulation has a relatively high guiding value to actual welding.Research on formability of welded joint shows that:Permeability and spreadability of weld increases with the increase of the laser power,and the diameter and back width of laser working area of the weld are increased,and weld width is not changed obviously.The increasing welding current can significantly improve permeability of the weld,but spread of weld metal has been reduced.With the increase of laser power,weld penetration of laser welding is increased.However,more metal elements were burned.Research on microstructures of welded joints show that:Heat affected zone of the grain near 2A12 aluminum alloy side was coarsening significantly,this situation in solid solution area is more serious;Grain of 7075aluminum alloy side is coarser than that of 2A12 aluminum alloy side;With the increase of laser power and welding current,the number of strengthening phases precipitated in solid solution area decreases,and columnar crystals of the upper part of weld are reduced.Columnar crystals on the upper 7075 aluminum alloy side of weld are more obvious,but weld grain was coarsened;In laser welding,crystal grains near laser fusion line are classic columnar crystals,and columnar crystals in the upper part are longer than that of the lower part.Research on mechanical properties of welded joints show that:With laser power and welding current increasing,location of the lowest microhardness moves away from weld.The laser power has little effect on the tensile strength and elongation of the welded joint.With the increase of welding current,tensile strength of welded joint decreases slightly and elongation increases.Fracture position move away from the weld direction in 2A12 aluminum alloy side.Effect of laser power on weld impact toughness is not particularly noticeable.As the welding current increases,impact toughness of weld zone decreases.Aging treatment can improve the overall mechanical properties of welded joints.Taking into account,Laser-MIG hybrid welding method is more suitable for dissimilar aluminum alloy welding.The optimum process parameters for laser-MIG hybrid welding are laser power 3.8 KW,welding current 195 A. |
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