Microstructural evolution of 6061-T6 aluminum alloy in vortex- friction stir welding

• Published in: Materials characterization Vol. 195; p. 112544
• Main Authors: Liu, X.C., Wang, Q., Pei, X.J., Li, Y.Z., Zhen, Y.Q., Shen, Z.K., Chen, H.Y.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.01.2023
• Subjects: Dynamic recrystallization; Friction stir welding; Microstructure; Precipitation; Vortex material flow; Precipitation; Microstructure; Dynamic recrystallization; Vortex material flow; Friction stir welding
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2022.112544

Vortex- friction stir welding (VFSW) is recently developed to avoid tool wear and breaking in conventional FSW. In VFSW, a vortex material flow is induced by a tool made of the identical material to the workpiece. The vortex material flow drives the adjacent material to flow and form welds. In this study, the microstructural evolution of 6061-T6 aluminum alloy in the VFSW process was investigated experimentally. Firstly, the microhardness and tensile strength of the VFSW joint were obtained to reflect the microstructure changes. Then, the grain structure and precipitate at different zones of the joint were characterized by EBSD and TEM, respectively. The results show that the heat affect zone (HAZ) is the weakest zone of the VFSW joint. The microstructure analysis suggests that the precipitate coarsening is the main reason for the heat softening in the HAZ. The continuous dynamic recrystallization occurs in the WNZ, but the recrystallization is insufficient due to the self-adapting but not mandatory plastic deformation in VFSW. Solid solution strengthening occurs in the WNZ due to the dissolution of precipitate at the high temperature during the VFSW process, which contributes to a higher microhardness value than that in the HAZ. •The microstructural evolution of AA6061-T6 during VFSW was investigated.•The HAZ is the weakest zone of the VFSW joint.•The precipitates coarsening leads to the severe softening of the HAZ.•The solid solution strengthening effect occurs in the WNZ.