Modified Friction Stir Welding of Al–Zn–Mg–Cu Aluminum Alloy

Friction Stir Welding (FSW) is adopted to join the Al-Zn-Mg-Cu (7xxx) aluminum alloys in order to improve strength and ductility of the joints. The paper presents an investigation on the effect of the modified FSW methods such as Impulse FSW (IFSW) and High-Speed FSW (HS-FSW) on the microstructure and mechanical properties of the AA7075 T6 aluminum alloy. It was demonstrated that the tensile properties and hardness of the IFSW joints could be improved compared to the traditional FSW joints by variation of the impulse parameters (force and frequency). This enhancement is caused by microstructural changes. The brittle fracture of the HS-FSW joints is explained by the presence of defects in the weld zone. It indicates that heat input was insufficient or intermixing in the stir zone was inadequate.