中文摘要：

采用三种不同针长的搅拌头对6082-T6铝合金板材进行焊接，获取三种类型的焊缝，即未透对接焊缝、已透对接焊缝和对．搭组合焊缝，通过对焊缝金相观察、拉伸测试和断口分析，得到焊缝类型对接头拉伸性能及断裂特征的影响规律。不同类型焊缝的表面成形区别不大，但内部成形各有特点。未透对接焊缝根部界面处形成未焊合缺陷；已透对接焊缝中无缺陷；对一搭组合焊缝后退侧和前进侧形成“钩状”缺陷。拉伸测试表明，未透对接接头拉伸性能最低，裂纹在未焊合处产生并沿焊核区扩展，接头下部呈现剪切断裂特征，接头上部呈现准解理和剪切混合断裂特征；已透对接接头拉伸性能最高，断裂位置位于前进侧热机影响区，断口呈现出典型的剪切断裂特征；对．搭组合接头拉伸性能居中，裂纹在前进侧“钩状”缺陷处产生并沿焊核区扩展，断口形貌与未透对接接头相似。

英文摘要：

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.