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S线作为搅拌摩擦焊一种典型焊接缺陷,对接头的力学性能影响较大。本文通过光学显微镜和扫描电镜观察,硬度测试和拉伸试验等方法,研究了S线的形成机制,并分析了其对2024-O铝合金搅拌摩擦焊接头组织演变及力学性能的影响规律。结果表明:在氧化层未去除的情况下,焊态接头未观察到S线,但随着焊后热处理温度升高,S逐渐显现并愈加明显。而对于去除表面氧化层的接头,无论是焊态还是热处理后均未观察到S线。焊后热处理温度较低时,S线对接头拉伸性能没有影响。然而,495℃固溶人工时效处理后,S线会显著降低接头的拉伸性能,抗拉强度相比无S线接头下降了17%,伸长率下降了94%。
S-line friction stir welding as a typical welding defects, the mechanical properties of joints greater impact. In this paper, the formation mechanism of S-line was studied by optical microscope, scanning electron microscope observation, hardness test and tensile test. The influence of S-line on microstructure and mechanical properties of 2024-O aluminum alloy friction stir welded joint was analyzed. The results show that S line is not observed in the welded joints without the oxide layer being removed. However, S gradually appears and becomes more obvious with the increase of the post-weld heat treatment temperature. For the joints with the surface oxide removed, no S-line was observed either after soldering or after heat treatment. Post-weld heat treatment temperature is low, S-line tensile properties of the joint has no effect. However, the S-line significantly reduced the tensile properties of the joints after solution treatment at 495 ℃ for 17 h, and the tensile strength decreased by 17% and elongation decreased by 94%, respectively.