Microstructure and Mechanical Properties of 6082 Aluminum Alloy Refill Friction Stir Spot Welding Butt Joint
Refill friction stir spot welding(RFSSW)is innovatively applied to butt welding of aluminum alloy.The effect of the tool rotating speed on the microstructure and properties of the 2 mm thick 6082 aluminum alloy butt welded joint was studied.The results show that incomplete bonding at the bottom part of the joint can be effectively avoided by using the tool plunge depth of 1.6 mm.When the rotating speed is 1950 r/min,hot crack appears on the outer edge of the stir sleeve retracting path.The grains of the stir zone is obviously refined,and when the rotating speed is 1350 r/min,the average grain size of the stir zone decreases from 30.84 μm of the base material to 8.43 μm.The textures of the thermal mechanical affected zone(TMAZ)and stir zone(SZ)change obviously.The hardness of the joint is generally higher than that of the base material,which is related to the smaller grains.When the rotating speed is 1650 r/min,the tensile strength of the joint is the maximum of 190 MPa.When the rotating speed is 1950 r/min,the tensile strength of the joint is only 121 MPa due to the cracks at the interface between the SZ and the TMAZ.
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