A characterization of microstructure and mechanical properties of A6N01S-T5 aluminum alloy hybrid fiber laser-MIG welded joint

A6N01S-T5 aluminum alloy is used widely on components of high-speed train body, such as the sidewall and underframe. Welded joints are often the positions where fracture and failure occur. In this paper, fiber laser-metal inert gas (MIG) welding was used as a new welding method to weld A6N01S-T5 alloy and compared with the traditional MIG welding joints. Optical microscopy, scanning and transmission electron microscopy, hardness tester, and electronic universal testing were used for the microstructure observation and mechanical property examination. Softening effect in the heat affected zone (HAZ) and weld fusion zone is observed. The precipitations and dissolution of beta' phases are proved to be the reason of softening. The tensile strength of the fiber laser-MIG welded joint was approximately 83 % of base metal, which is 33 MPa higher than that of the MIG welded joint. The fracture position of the joints is in accordance with the lowest hardness position.