搅拌头停留时间对6082铝合金搅拌摩擦点焊接头组织和力学性能的影响

Effect of stirring tool dwell time on the microstructure and mechanical properties of friction stir spot-welded 6082 aluminum alloy joints

采用光学显微技术、显微硬度和拉伸测试,研究了不同搅拌头停留时间对6082铝合金搅拌摩擦点焊接头显微组织和力学性能的影响。结果表明,接头由搅拌区、热机影响区、热影响区和母材区组成。搅拌区形成了细小的再结晶等轴晶粒,并且在其附近形成"Hook"区。搅拌区硬度和接头断裂载荷随着搅拌头停留时间的延长而不断增大,但趋势逐渐变缓。在搅拌头旋转速度为1 400 r/min,停留时间为20 s时,接头断裂载荷达到最大值,为3.56 kN。点焊接头在拉伸测试过程中的失效方式是韧-脆混合型断裂。

The effect of stirring tool dwell time on the microstructure and mechanical prop- erties of friction stir spot-welded （FSSW） 6082 aluminum alloy joints were investigated by optical microscopy, microhardness and tensile tests. The results show that friction stir spot welding joints consist of stir zone （ SZ）, thermo-mechanically affected zone, heat affected zone and base metal. ＂Hook＂ zone is formed near the stir zone, which consists of equiaxed fine grains. As dwell time increases, the hardness value of the stir zone and the fracture load of the joints increase, but the increasing speed goes down. When rotation speed is 1 400 r/min and dwell time is 20 s, the fracture load reaches its peak value （3.56 kN）. The frac- ture mechanism of the joints is ductile and brittle mixed fracture.