Microstructure, texture and mechanical properties during refill friction stir spot welding of 6061-T6 alloy

The evolution of microstructure, texture and mechanical properties during refill friction stir spot welding (RFSSW) of 6061-T6 alloy was investigated in the present paper. The Electron backscattering diffraction results revealed that a significant volume of A/-A, and B/-B component of shear textures was formed in the weld. The sleeve inner wall governed the formation of shear texture beneath the sleeve and pin. Whereas, the shear texture at the sleeve periphery was associated with the material flow when material was discharged from the bottom of the thread on the rotating sleeve. The microstructure evolution in the RFSSW of 6061-T6 alloy was dominated by continue recrystallization. However, the grain boundary bulging and presence of cube texture indicated that the discontinue recrystallization also participate in the grain evolution. The tensile shear strength had a negative correlation with the hook height.