Research On Friction Stir Welding With Filler Wire Process Of 5A06 Aluminum Alloy And Q235 Cold Rolled Steel

5A06 aluminum alloy plate and Q235 low carbon steel plate were chosen to have a test of the aluminum/steel wire-filled friction stir butt welding.It studies the influence of the welding wire alloy system and the friction stir welding process parameters on the weld macroscopic morphology,interface micro-structure morphology,joint mechanical properties and interface element diffusion distribution and fracture morphology.And also studied the the distribution rule and measured the friction factors of different aluminum/steel friction.The distribution impact of the peak residual stress after welding was further discussed on the toughness of welding.The experiment firstly discovered different welding alloy systems have impact on macroscopic morphology of the weld seam,the micro-structure of the interface,the mechanical properties of the physical joint and the distribution of different element diffusion.With the increasing of Si content,the weld seam is more beautiful,the number of the steel grains becomes more and the size of them becomes larger.When welding with Al-12%Si,there are some holes in the welding surface,by contrast,when using Al-9%Si,the welding wire shows a good appearance and the tensile strength of the weld can even reach at 216.7MPa.However,under that circumstance,the metallic compounds of Fe and Al contents appeared in the surface resulted in a worse plasticity,toughness and bending properties.When using Al-9%Si-4%Cu welding wire,the surface of welding seam shows a good appearance,and the size of the steel particles becomes larger as well as the number of them is decreased.At the same time,the average bending angle of the joint increases slightly while the welding strength is clearly growing weaker.With the increasing element of Ni in Al-9%Si-4%Cu,the abrasive resistance,such as Al₂Cu,AlNi elements,appears near the area of the interface and becomes more.The Cu and Ni element of IMC layer will be softened,and the joint strength and plastic toughness will also be improved.The best performed stir friction welding joint of aluminum/steel can be obtained from Al-9%Si-4%Cu-6%Ni welding wire,its average tensile strength of the joint can reach at 240.3Mpa,the positive bending angle reached at 19.3°and the back bending angle reached at 13.4°.The research then discovered how these three process parameters-welding wire thickness D,heat input factor M,indentation amount H,influence the macroscopic morphology of the weld,the micro-structure of the interface,the mechanical properties of the joint and the element diffusion distribution.The test results show that the optimized process parameters can greatly improve the weld morphology and mechanical properties of aluminum/steel dissimilar metals.As the process parameters increases,the average tensile strength and average bending angle increase firstly and then decrease.As the thickness of welding increases,the weld filling effect will be improved,and the defect disappears,and the abrasive resistance of AlNi and Al₂Cu increases,while the range of distribution becomes large first and then decreases.When the heat factor“M”was increased,the degree of plasticization of the weld metal act more clearly and the plasticized metal can be more fully mixed,stirred,and react with each other.As the indentation amount“H”increases,the the greater pressure of the mixing needle was improved,even limits the metal flowing,the distribution of steel particles will be more concentrated.The performance of the joint is more sensitive to the amount of the indentation“H”.When the welding wire thickness d equals 1.0mm,heat input factor m equals 5,and press-in amount d equals 0.3mm,the joint shows the best performance,and the joint tensile strength and bending angle reach the maximum,which the average strength is 240.1MPa,the maximum average bending angle of the joint is 19.3°for forward and 13.4°for back bend.The test analyzes the rule of peak residual stress distribution after welding.The peak residual stress at the interface is the largest.The farther away from the interface,the peak residual stress is smaller.With the increase of Si,Cu,Ni elements,the reaction efficacy between Fe/Al element will be restricted,so that the thickness and hardness of the IMC layer are reduced,and the peak residual stress in the weld will also reduced.As the thickness of the welding wire increases,the temperature in the weld decreases and the aluminum steel metal will be easily expanded or shrank,so the peak residual stress of each test point of the sample decreases at varying degrees.