(Session 6A)Mechanical Properties and Flow behavior of Pinless Friction Stir Spot Welded Joint of 2024 aluminum alloy

摘要

A pinless tool with involute grooves on its shoulder surface has been used to friction stir spot weld (FSSW) the 1.5mm thick 2024-T3 aluminum alloy plates. Effects of the rotational speed, plunge rate and dwell time on the formability and mechanical properties of the FSSWed joints were investigated. Results showed that the keyhole intrinsic to the conventional FSSW having a pin could be completely avoided and a smooth joint surface was achieved. The maximum tensile-shear strength of the joint was found to be 6.95kN. Besides, the distribution of Vickers hardness profile shows an M-shape, where the maximum hardness is in the nugget zone. Furthermore, two different nugget pullout failure modes could be observed. One failure mode starts from the hook which is located at the periphery of the nugget zone. Another failure mode originates from the interface of the two plates. In addition, flow behavior of weld metal was researched using the finite-element method and the experiment methods. Based on the results, the flow mode of the pinless tool FSSW process was proposed.