35mm厚板铝合金搅拌摩擦焊接头组织和性能

Microstructure and properties of 35mm thickness aluminium alloy welded joint by friction stir welding

采用搅拌摩擦焊双面焊工艺,对35 mm厚板6005A-T6铝合金型材进行了搅拌摩擦焊接,获得成形良好、表面光滑、无隧道孔和沟槽缺陷的焊接接头.应用光学显微镜、扫描电镜、显微硬度仪及电子拉伸试验机等对搅拌摩擦焊接头组织与性能进行研究.结果表明,接头焊核区组织为细小等轴晶;前进侧出现明显的螺旋纹及清晰的结合线,热力影响区晶粒被明显拉长呈条状组织,热影响区受热晶粒粗大;后退侧未见螺旋纹,晶粒比前进侧细小,过渡区较前进侧宽.在搅拌头旋转频率为650 r/min,焊接速度为200 mm/min工艺条件下接头抗拉强度为213 MPa,达到母材强度的84.8%,断裂起始于焊缝前进侧的热影响区,扩展至双面焊接重合区时,沿着焊缝后退侧热影响区直至断裂;接头显微硬度最低值出现在前进侧热影响区,最低值为50 HV.

Joints of 35 mm thickness 6005A-T6 aluminum alloy by friction stir welding on both sides were obtained,and formation of weld is well and there are no defects such as tunnel defect,hole and groove defect,etc.Microstructures and properties of weld joint by friction stir welding have been studied by scanning electron microscope optical microscope and electron and tensile testing machine.Experimental results show that equiaxial crystal is formed in weld nugget zone,visible spiricle and clear comb line are formed in advancing side,and the grains are elongated and banded structuree are formed in thermal-mechanical affected zone,coarse grains are formed in heat affected zone;The fine crystal grains are formed and there are no spiricle in transition zone of retreating side.The tensile strength reached 213 MPa at rotation speed of 650 r/min and welding speed of 200 mm/min,and the tensile strength reaches 84.8% of base metal.Fracture occurred in heat affected zone of advancing side;The lowest microhardness is about 50 HV which is in heat affected zone of advancing side.