铝合金厚板FSW焊缝成形及金属流动行为分析

采用三角平面圆锥形搅拌针焊接20 mm厚的铝板，分析工艺参数对焊缝成形及金属流动特征影响。随着旋转速度增加，单位时间内金属迁移量增大，焊核区面积增加，疏松区面积减小至消失；而过大的旋转速度反而使疏松缺陷再次出现。适当减小焊接速度，增大单位长度内焊缝热输入，改善焊缝成形，但焊接速度过小易导致焊缝上部受热过多，疏松区及内部孔洞变大。在合适的参数下焊接时，瞬时空腔的出现可使更多塑化金属绕搅拌针做圆周迁移，即提高了沿水平方向的“抽吸-挤压”效应，改善了金属流动性，减少甚至消除焊缝内部缺陷。

Weld formation and material flow behavior in FSW thick aluminum alloy plates

7075-T6 aluminum alloys of a thickness of 20 mm are friction stir welded using a tapered pin with three flats, and the effect of process parameters on weld formation and local flow characteristic are investigated. With the increase of the rotation speed, the area of nugget increases due to the increase of the amount of plastic metal migration in unit time, and the area of loose zone decreases and even disappears. When the rotation speed is too high, the loose defect emerges again. Decreasing the welding speed appropriately can improve the weld quality by increasing the heat input in unit length, and the defect is gone. A lower welding speed causes a bigger loose zone and many internal voids because of more heat input. In the welding under appropriate parameters, more plastic materials horizontally migrate around the rotary pin with the appearance of the temporary cavity, and the "sucking-extruding" effect along the horizontal direction can thus be enhanced, improving the flowability and eliminating the internal defects.