The current work aims to study the effects of stirring pin morphology on the FSWed lap joints defects and mechanical properties. The 2A12 aluminum alloy friction stir welding lap joints were obtained using two shapes and three thread lengths of stirring pins by experiments. Besides the interface defects forming mechanism were studied by joints plastic metal flow numerical simulation. The results show that the conical pin can lead to uniform and continuous plastic metal velocity field which forms a Hook defect with sharp end, smaller deflection angle (minimum 8°) and larger size (maximum 0.18mm). It also will lead to a larger failure load (maximum is 9.5kN), and the fracture position easily occurs at the Advancing side (AS) of lower plate. The three section pin has a periodic shearing effect causing velocity difference between the arc edge and cutting section of the pin which forms a Hook defect with thicker end, larger deflection angle (maximum 42°) and smaller size (minimum 0.06mm). It also causes discontinuous wavy debris forms in the AS. The three section pin leads to a lower failure load (maximum is just 7.6kN), and the fracture position turns to occur at the lap interface. The increase of the thread length can promote the exchange of plastic metal in the thickness direction and interface materials flow velocity. So the angle (from 20°to 150°) and size (from 0.1mm to 0.6mm) of Hook increases but the height of Cold Lap reduces (increasing the effective sheet thickness of retreating side from 0.69mm to 0.95mm). In addition, the increase of the thread length can make the periodic shear effect of three section pin gradually weak. It is also found that the fracture position is closely related to the shape and the thread length of pins. When using conical pin, the fracture occurs at AS of lower plate or Retreating Side of Nugget Zone (NZ-RS) of upper plate; When using three section pin, the fracture occurs at the bonding interface. And with the increase of the thread length, the fracture position changes from the bonding interface to the NZ-RS of upper plate, and finally to the AS of lower plate.

当前的工作旨在研究搅拌销形态对FSWed搭接接头缺陷和力学性能的影响。利用两种形状和三种螺纹长度的搅拌销，通过实验获得了2A12铝合金摩擦搅拌焊接搭接接头。此外，还通过接头塑性金属流动数值模拟研究了界面缺陷的形成机理。结果表明，锥形销可导致均匀且连续的塑性金属速度场，从而形成具有尖锐末端，较小的偏转角（最小8°）和较大的尺寸（最大0.18mm）的钩形缺陷。这也将导致更大的破坏载荷（最大为9.5kN），并且断裂位置很容易出现在下板的前进侧（AS）。三段式销钉具有周期性的剪切作用，导致销钉的弧形边缘与切割段之间产生速度差，从而形成钩形缺陷，其端部较厚，偏转角较大（最大42°）且尺寸较小（最小0.06mm）。它还会在AS中导致不连续的波浪形碎屑形式。三段式销导致较低的失效载荷（最大仅为7.6kN），并且断裂位置在搭接界面处发生。螺纹长度的增加可以促进塑性金属在厚度方向上的交换和界面材料的流动速度。因此，挂钩的角度（从20°到150°）和尺寸（从0.1mm到0.6mm）增加，但是冷弯的高度减小（后退面的有效板厚从0.69mm增加到0.95mm）。此外，螺纹长度的增加会使三节销的周期性剪切作用逐渐减弱。还发现断裂位置与销的形状和螺纹长度密切相关。当使用锥形销时，断裂发生在下板的AS或上板的掘金区的后退侧（NZ-RS）；当使用三段式销钉时，断裂发生在粘结界面处。随着螺纹长度的增加，断裂位置从粘结界面到上板的NZ-RS，最后到下板的AS发生变化。当使用三段式销钉时，断裂发生在粘结界面处。随着螺纹长度的增加，断裂位置从粘结界面到上板的NZ-RS，最后到下板的AS发生变化。当使用三段式销钉时，断裂发生在粘结界面处。随着螺纹长度的增加，断裂位置从粘结界面到上板的NZ-RS，最后到下板的AS发生变化。