A novel non-keyhole friction stir welding technique was proposed to weld the butt joint of 6061-T6 aluminum alloy with the thickness of 6 mm. A sound joint was obtained by this technique, simultaneously eliminating the flash, shoulder mark and keyhole defects. The sleeve directly affected zone (SDAZ) and the sleeve indirectly affected zone (SIAZ) were divided into the joint according to the plunging position of the hollow sleeve. The lack of root penetration defect was avoided when the plunging depth of the hollow sleeve was only 4.2 mm, because the hollow part inside the sleeve improved the material flow below the sleeve. An S-shaped line was left at the SIAZ, and the height of it had the minimum value of 1.47 mm at 20 mm/min. Whether the failure location of the joint was in SIAZ/SDAZ or the heat-affected zone (HAZ) depended on the height and bonding strength of the S-shaped line. The joint fracture location changed from the SIAZ/SDAZ at 35 mm/min to the HAZ at 20 and 30 mm/min. The maximum tensile strength of 224.3 MPa was obtained at 30 mm/min which was 73.7% of that of the base material. The fracture surface morphology exhibited the typical ductile fracture.

提出了一种新型的无匙孔搅拌摩擦焊焊接6061-T6铝合金的对接接头，厚度为6 mm。通过这种技术获得了良好的接头，同时消除了毛边、肩痕和锁孔缺陷。套筒直接影响区（SDAZ）和套筒间接影响区（SIAZ）根据空心套筒的插入位置分为接头。当空心套筒的插入深度仅为4.2 mm时，避免了无根穿透缺陷，因为套筒内部的空心部分改善了套筒下方的材料流动。在 SIAZ 处留下一条 S 形线，其高度在 20 mm/min 时的最小值为 1.47 mm。接头的失效位置是在SIAZ/SDAZ还是热影响区（HAZ）取决于S形线的高度和结合强度。接头断裂位置从 35 mm/min 的 SIAZ/SDAZ 变为 20 和 30 mm/min 的 HAZ。在 30 mm/min 下获得的最大拉伸强度为 224.3 MPa，是基材拉伸强度的 73.7%。断口形貌表现出典型的韧性断裂。