| Friction stir welding(FSW)is an efficient,environmental and quality welding technique,which is developed in nearly 20 years and widely used in welding lightweight alloy,especially aluminum alloy.Friction stir tool is the only consumable and the key f actor in the friction stir welding process.In order to obtain high quality welds the tool must be matching.In this paper 2024 aluminum alloy was welded by friction stir welding(FSW)in tapered thread pin tool.The right welding process window is found by a large number of experiments,and by comparing the organization and performance of the component found that when the rotation speed is 800 rmp and welding speed is 80mm/min,the inclination of spindle is 2 °and preheating time is 15 s,the tensile stren gth of the weld highest,reached 364.29 MPa,accounting for 80.95 % of the base material.The effect of different tool pin profiles on mechanical properties testing and microstructure analysis of 2024 aluminum alloy joints using friction stir welding technique was investigated.Four different tool pin profiles: threaded tapered cylindrical(1#),Conical cam thread(2#),triangular pyramid(3#)and eccentric taper thread(4#)were used to produce the joints.The results indicate that all the tools can weld goo d joints and the joint by triangular pyramid tool pin profile has an unbroken onion ring on the across-section and the grain size of weld nugget zone(WNZ)is 5-11?m,which is least compared with others.The least micro-hardness of the joint appears between the heat affected zone(HAZ)and the thermo-mechanically affected zone(TMAZ)and the value of the joint welded by triangular pyramid tool pin profile is higher than other joints.The welding longitudinal residual stress of all joints is a “M” shaped,the relationship is 4 #>1 #>2# >3#,which is similar to levels of temperature field.All joints tensile strength reached more than 80% of the parent metal,but triangular pyramid tool pin profile has the highest tensile strength.Tensile strength of the joint is 394.74 MPa that can reach 87.72% of the base metals and elongation is 15.38%.The fracture surface shows that the fracture mode of the joints is plastic fracture.Comparing the effects of different aging processes on the joint of 2024 aluminum alloy by FSW,found that 150 ? +170 ? artificial aging the number of second-phase particles was increased and not grown up,The micro-hardness of the joint between the heat affected zone(HAZ)and the thermo-mechanically affected zone(TMAZ)is highest,which reached 110 HV,and the tensile strength was increased 31 MPa,which up to 391 MPa.Analysis the fracture of the joint which after aging,found that the fracture was belong to plastic fracture.So the best aging pr ocess in 2024 aluminum alloy is 150 ? + 170 ? artificial aging. |
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