套筒设计对异种铝合金回填式搅拌摩擦点焊接头成形的影响

Low joining efficiency and defects are the main obstacles for the industrial application of refill friction stir spot welding (Refill FSSW). Threaded and grooved sleeve tools were applied to refill FSSW Al6022/Al7075 dissimilar welds. The results indicated that compared to that of a threaded sleeve tool (conventional refill FSSW), an arc-structured was formed around the weld, in which the top and bottom sheets materials were mixed together, when the weld was fabricated using a grooved sleeve tool (modified refill FSSW). The material flow performance in the thickness direction can be significantly improved, when the weld was fabricated using a threaded sleeve tool via a fast plunging rate (fast plunging refill FSSW). Also, metallurgical and mechanical interlocking joining mechanisms were confirmed at the interface. Furthermore, material inter-mixing increased with the increasing of welding time, when the weld was fabricated using a grooved sleeve tool via fast plunging rate (grooved sleeve and fast plunging refill FSSW). The maximum temperature was 504.3 ℃ during modified refill FSSW, and melting of MgZn₂ resulted in liquation cracking. Based on the fundamental of heat generation, weld stability and strength and be improved by modified and fast plunging refill FSSW, defect-free weld that meet requirement of the industry can be fabricated using grooved sleeve and fast plunging refill FSSW within 1 s.