Fig. 1 Coupling between the thermal and mechanical processes in friction stir welding

Fig. 2 Frictional force at the tool/workpiece interface. Reprinted from Zhang et al. [66], Copyright (2018), with permission from Elsevier

Fig. 3 Calculated heat flux at the tool/workpiece interface. a Unthreaded pin, b threaded pin. Reprinted from Sun et al. [67], Copyright (2018), with permission from Elsevier

Fig. 4 a Top view of the plate at steady state, b section view through the center of the tool at steady state. The temperature scale is degrees Celsius. Reprinted from Miles et al. [73], Copyright (2019), with permission from Elsevier

Fig. 5 Comparison of the defect along welding direction for 0° tilt angle. a Experimental, b simulation. Reprinted from Chauhan et al. [52], Copyright (2018), with permission from Elsevier

Fig. 6 Simulation predicted effective plastic strain along the welding direction for the tilt angle of 2°. Reprinted from Chauhan et al. [52], Copyright (2018), with permission from Elsevier

Fig. 7 Comparison of the joint area morphology. a Tracing particle distribution in the observation plane after moving through the tool area (Sim-1.1-1.5), b Sim-2.1-2.5, c wormhole defect distribution in the nugget area after the experiment. Reprinted from Zhu et al. [68], Copyright (2016), with permission from Elsevier