Study On The Process And Properties Of Laser-TIG Hybrid Welded Joint Of Aluminum Alloy

Aluminum alloys are extensively used in aviation,aerospace,vehicle traffic,vessel and other fields due to their light weight,high specific strength,good corrosion resistance,and excellent mechanical properties.Aluminum alloys also possess good weldability.At present,almost all of the fusion welding processes and the solid joining process are used in the joining of aluminum alloys.As a green welding technology,low-power laser-arc hybrid welding process is energy-efficient and has gotten a good application in the welding of titanium alloy,magnesium alloy,steel and dissimilar metals.The hybrid heat source will be further applied in aluminum alloys.In this paper,lower-power laser-TIG hybrid heat source is used to the welding of 3 mm thick 6061-T6 and 2 mm thick 7005 aluminum alloy sheets with cold filler wire and the filler wire used is ER5356.For 6061-T6 aluminum alloy,the influence of process parameters on weld shape and gas pores,and the feeding condition of filler wire,the main process parameter that influences the sizes of weld seams are investigated.The mechanical properties,microstructure of the joints,the effects of only artificial aging treatment(only vary artificial age-hardening times at 155℃),the combination of solution and aging treatment(the solution treatments are carried out at different temperatures for a soaking period of 1 h followed by artificial aging treatment at 155℃ for 8 h)on the mechanical properties and microstructures of the joints are analyzed in the work.For 7005 aluminum alloy,the effects of process parameters on the formation of weld in butt welding with filler wire are studied.It is hoped that it can provide theoretical and technical supports for the application of hybrid low-power laser-TIG welding heat source in aluminum alloy welding.The conclusions of the hybrid laser-TIG welding of 6061-T6 aluminum alloy are as follows: In the condition of overlay welding without filler wire,the weld geometry sizes increase with the increase of arc current;the weld sizes decrease with the increase of welding speed;weld joint with no pore can be obtained by adjusting process parameters.In the condition of the bead-on-plate weld with filler wire,the process possesses high stability,and the filler wire is transited into the welding pool through a molten metal bridge when the distance between laser and arc is in the range of +1~+3.75 mm.When the wire feeding angle is 50 degrees,the wire feeding speed can be adjusted within a wide range.In butt welding with filler wire,the welding parameters that influence the weld geometry sizes in descending order are arc current,welding speed,laser power.The main parameters that affect the fusion width,face reinforcement and root reinforcement are laser power,arc current and arc current,respectively.The ultimate tensile strength and elongation of the desired welded joint are 213.9 MPa and 15.2%,respectively,and those of the base metal are 340 MPa and 14.84%,respectively;the artificial aging treatment has no obvious improvement on properties of the joint;when treated by the combination of solution and aging treatment,the joint is softened due to the grain coarsening with the temperature of 475℃.The best mechanical properties of the hybrid welding joint are obtained at the temperature of 520℃ of which the ultimate tensile strength and elongation reach 285.78 MPa and 20.37%,respectively.The joint undergoes overburning when the temperature of solution treatment is 565℃.The TEM analysis of the optimal joints under only artificial aging treatment and the combination of solution and aging treatment show that the difference between the two treatments is related to the quantity,morphology and distribution of the hardening precipitates and the distribution of the dislocations.The results of the hybrid laser-arc welding of 7005 aluminum alloy are as follows: the welding process has strong adaptability to 7005 aluminum alloy;the grains in the heat affect zone still keep the grain structure of the base metal;the ultimate tensile strength and elongation of the welded joint are 91.73% and 73.92% of the base metal,respectively;the distribution of alloy elements in each zone is more uniform and there is no obvious fluctuation.