搅拌针表面形状对焊缝金属轴向迁移的影响

采用不同表面形状的搅拌针对20 mm厚7075铝板进行焊接，分析其对焊缝金属沿轴向迁移的影响.结果表明，使用圆锥形搅拌针焊接时，随着旋转速度增加，焊核区面积、塑化金属沿两边向上迁移高度先增大后减小，疏松区面积则先减小后增大.同一焊缝中焊核区内塑化金属沿前进边向上迁移高度大于返回边.采用375 r/min旋转速度焊接时获得的焊核区面积、塑化金属向上迁移高度最大，疏松区面积最小.而使用三角平面搅拌针焊接时，瞬时空腔的出现增强了沿焊缝水平方向上"抽吸-挤压"效应，同时改善塑化金属沿轴向上的流动性，导致疏松缺陷消失.

Effect of pin surface profile on axial flow behavior of plastic material in friction stir welds

AA7075-T6 thick plates with 20 mm thickness were friction stir welded by using tools with various pin surface profiles, and the effect of pin surface profile on flow behavior of plastic material along axial direction of weld was analyzed. The results showed that, when the tool with a taper thread pin was applied, the area of nugget zone and the transfer height on two sides in the welds increased firstly and then decreased with increasing rotation speed, while the area of loose zone firstly decreased and then increased. Moreover, the transfer height of plastic material on the advancing side was bigger than that on retreating side in the same weld. As a rotation speed of 375 r/min was used, the biggest area of nugget zone and transfer height on two sides while the smallest one of loose zone were obtained. However, the transient cavities can promote the sucking-extruding effect along the horizontal direction of the weld when the tool with a triangle taper thread pin was used during FSW. Also, the flowability of plastic material was improved along axial direction. Therefore, the loose defect in the weld was removed.