Effect of welding parameters on mechanical and fatigue properties of friction stir welded 2198 T8 aluminum–lithium alloy joints

The main friction stir welding parameters include the rotation speed (ω) and the welding speed (v). 2198 T8 welded samples were designed to investigate effects of the ratio ω/v on the microstructure, the microhardness and tensile properties of welds. Fatigue tests were performed under three different R ratios, and crack growth rates were compared. The fractographic analysis was performed by SEM to analyze the fracture mechanism. It is shown that microhardness and tensile strength of the joints through the weld decrease with increasing ω/v. The fracture pattern has a tendency to change from the brittle fracture to the ductile fracture.