旋转速度对镁/铜异种金属搅拌摩擦焊接头成形及拉伸性能的影响

保持95 mm/min焊接速度不变的条件下，通过改变旋转速度研究其对镁/铜异种金属搅拌摩擦焊接头成形和力学性能的影响。结果表明:采用750 r/min搅拌头旋转速度焊接时，焊缝表面出现起皮现象；焊核区底部形成明显的隧道槽缺陷。适当增加搅拌头旋转速度至950 r/min时，焊缝表面变得更光滑；混合区尺寸增大；内部隧道槽缺陷消失；该混合区主要由被搅碎的Mg、Cu合金和少量新生成的Mg₂Cu金属间化合物组成；接头的抗拉性能最好，抗拉强度达81.7 MPa；但是，继续增大搅拌头旋转速度至1180 r/min时，不利于接头成形，混合区底部有细小的孔洞缺陷产生。

Effect of Rotation Speed on Formation Quality and Tensile Properties of Friction Stir Welding Dissimilar of Mg/Cu Alloys Joints

In this work, maintaining the welding speed at 95 mm/min, effect of rotation speed on formation quality and tensile properties of friction stir welding dissimilar of Mg/Cu alloys joints was studied. The results show that, there are some flash on the weld surface and obvious tunnel channel defect on the bottom of the weld nugget zone when a low rotation speed of 750 r/min is applied. With increasing rotation speed to 950 r/min, the weld becomes smoother, the size of the weld mixed zone enlarges and the tunnel channel defect in the weld mixed zone disappears. The micro-structure of the weld mixed zone is comprised of broken copper-magnesium alloys and a small amount of Mg₂Cu intermetallic compound. Moreover, the tensile performance of the joint is the best with the average tensile strength high up to 81.7 MPa. However, continuously increasing the rotation speed to 1180 r/min, some small holes form on the bottom of the weld mixed zone, which is not conducive to the joint formation.