Effects of Weld Characteristics on Tensile Properties and Fracture Morphologies of Friction Stir Welded Joints

doi:10.3901/JME.2015.22.029

Abstract

Abstract: Three different-pin-length tools are utilized to weld 6082-T6 aluminum alloy plates in order to obtain three kinds of welds, namely, lack-of-penetration butt(LPB) weld, complete-penetration butt(CPB) weld and butt-lap(BL) weld. The effects of weld characteristics on tensile properties and fracture morphologies of friction stir welded joints are studied by metallographic observation, tensile test and fracture analysis. Different kinds of welds have the analogical crown appearance and unique inner morphology. Root flaw is formed at the faying surface of the LPB weld, welding defect is not found in the CPB weld, and Hook defects can be observed both on the retreating side(RS) and advancing side(AS) in the BL weld. The crack originates from the root flaw and propagates along the nugget zone in the LPB joint which has the lowest tensile property, and the fracture surface shows a shear fracture in the lower part and shows a mix of quasi-cleavage fracture and shear fracture in the upper part. The CPB joint is fractured in the thermal-mechanically affected zone on the AS and has the highest tensile property, and the fracture surface exhibits a shear fracture. For the BL joint which has the tensile property between the LPB joint and BL joint, the crack occurs along the Hook line on the AS and extends in the nugget zone, and the fracture morphology is similar to that of the LPB joint.

Key words: fracture morphologies, tensile properties, weld characteristics, welding defects

LIU Huijie, LIU Xiangqian, HU Yanying. Effects of Weld Characteristics on Tensile Properties and Fracture Morphologies of Friction Stir Welded Joints[J]. Journal of Mechanical Engineering, 2015, 51(22): 29-34.

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