Non-weld-Thinning Friction Stir Welding

Regardless of conventional fiction stir welding (FSW) (Nandan et al. in Prog Mater Sci 53:980–1023, 2008 [1]) or its derived welding technologies (Wang et al. in J Mater Sci Technol 33:1009–1014, 2017 [2]; Sree Sabari et al. in J Manuf Process 22:278–289, 2016 [3]), weld thinning always forms at the joints and easily results in the strength loss. This is because that a rotating shoulder plunges into the welding workpieces to a certain thickness (≥ 0.05 mm, which is determined by the thickness of the workpieces) to produce intense frictional heat and result in the overflow of the plasticized materials.