Employing hooking and effective sheet thickness to achieve optimum failure load in lap joints of friction stir welded AA5456 aluminum

摘要

Friction stir welding process is a suitable process for joining AA5000 alloy series as it does not have associated with such problems of fusion welding especially in lap joint configuration; however, optimization of process parameters would be inevitable. In this study, the effects of tool rotation rate and welding traverse speed on the failure load of AA5456 lap joints having different sheet thicknesses were investigated. While processing, rotating tool was plunged through AA5456-H321 upper sheet (t = 5 mm) surface into AA5456-O bottom sheet (t = 2.5 mm). Rotational speeds in the range of 300-1000 rpm at constant traverse of 30 nun min(-1) and traverse speeds in the range of 15-100 mm min(-1) at constant rotations of 600 rpm were applied for fabrication of specimens. Macrostructure of weld cross sections were studied and for mechanical characteristics, shear-tensile tests were performed and compared in all conditions. Meanwhile, fracture surfaces of examined samples were studied using scanning electron microscope. The results of shear-tensile tests revealed that welding parameters of 600 rpm and 30 mm min(-1) were the optimal combination to achieve utmost failure load in this study. Shear failure occurred in the base metal of joined materials due to employing the optimum height and orientation of hooking.