Quasi-in-situ investigation into the microstructure and texture evolution of pure magnesium during friction stir welding

Abstract

The quasi-in-situ microstructure and texture evolution along the real flow path of pure magnesium during friction stir welding were investigated. Five representative stages were involved from the base metal to the formation of the final stir zone. The material experienced compression, preheating, acceleration, deceleration, and subsequent annealing over the course of the welding process. A highly concentrated (0001) texture, denoted as “orientation convergence”, was initiated at the beginning of the acceleration stage (shearing deformation zone) in front of the tool. Both continuous and discontinuous dynamic recrystallization occurred simultaneously in the stir zone, and continuous dynamic recrystallization was determined to be the primary recrystallization mechanism. The marker material morphology and EBSD data were used to elucidate the in-situ evolution of the shear direction and shear plane along with the real flow path.