Research Progress of Bobbin Tool Friction Stir Welding of Aluminum Alloys: A Review

Bobbin tool friction stir welding (BT-FSW) is a variant of conventional friction stir welding (FSW). It can be used to weld complex curvature structures and closed sections by adding an extra shoulder instead of a rigid backing anvil, which expands the potential application of FSW in aerospace, railway, automotive and marine industries. BT-FSW has some significant advantages over conventional FSW such as no root flaws, full weld penetration, low stiffness requirements for machines and fixtures, balanced heat input, lower distortion and thus has broad prospects for development. At present, there have been numerous research reports on BT-FSW, but its widespread use is still restricted due to various factors such as tool life, process stability, control complexity and implementation cost. In this paper, the domestic and foreign research progress of BT-FSW is reviewed from four aspects of bobbin tool design and classification, temperature field and flow field during welding, microstructure and mechanical properties of welded joints as well as industrial application, and then the possible research hotspots of BT-FSW in the future are pointed out. This paper mainly aims to help researchers have a comprehensive and in-depth understanding of BT-FSW.