复合搅拌摩擦点焊接头的金属流动行为

Metallic Flowing Behavior of Com-stir^(TM) Friction Stir Spot Welding Joint

研究了LF21铝合金在复合搅拌摩擦点焊时焊点金属的流动行为,并将复合搅拌摩擦点焊与直插式搅拌摩擦点焊的接头性能进行了对比。研究结果表明:LF21铝合金的复合搅拌摩擦点焊焊点的金相组织存在4个区域——母材区、热机械影响区、热影响区、塑性环区;与直插式搅拌摩擦点焊不同的是,在塑性环的边上形成了一个由复合搅拌形成的"耳朵形"区域,并且左右不对称,因此增加了塑性环的宽度;热机械影响区域与热影响区交接面的金属形成向上流动的塑性流,热影响区两侧金属的流动具有对称性,金属的流动行为类似于羽毛状;复合搅拌摩擦点焊焊点的剪切力比直插式搅拌摩擦点焊的提高了40%。

To analyze the metallic flowing behavior of the com-stir^TM FSSW （friction stir spot welding） joint and compare its mechanical properties with the common FSSW joint, the LF21 aluminum alloy is used in the investigation. Results show that the microstructure of the com-stir^TM FSSW joint of LF21 aluminum alloy contains four zones,namely the base metal zone, the thermo-mechanical-affected zone, the heat-affected zone and the plasticity ring zone. Different from the FSSW, the com-stir^TM FSSW can form an asymmetric so-called ear zone beside the plasticity ring and therefore widen the plasticity ring. The metal in the interface of the thermomechanical-affected zone and the heat-affected zone can form an upward plastic flow. The metallic flowing behavior appears featheriness and symmetry on both sides of the heat-affected zone. The shear strength of the com-stir^TM FSSW joint is about 40% higher than that of the common FSSW joint.