Friction stir welding characteristics of aluminum alloy plates with different thickness

Friction stir welding (FSW) of strain-hardened, 3mm-thick and 5mm-thick AA1050-H24 aluminum alloy plates were performed to examine and reveal the effect of plate thickness on the friction stir welding characteristics. The results indicate that the plate thickness has little effect on the weld morphology, and the weld defects in the different-thickness plates are significantly different. The FSW parameters have different-extent effects on the tensile properties for the different-thickness joints. The greater the thickness of plate, the more significant the effect of the parameters, and thus the more narrow the selective range of the parameters. The different-thickness joints have clearly different fracture location characteristics. When the revolutionary pitch (RP) is smaller than a certain critical value, the joint for a thin plate tends to fracture on the retreating side, while the one for a thick plate is prone to fracture on the advancing side. When the RP is greater than the critical value, the joint is fractured in or near the weld center.