Fatigue crack growth rate and mechanical properties of one-step double-side friction stir welded AA6061-T6

Friction Stir Welding (FSW) is commonly used in transportation industries but faces challenges when joining thick plates. To address this, double-side FSW (DFSW) has been introduced, involving two steps: FSW on one side, flipping the plate, and then FSW on the opposite side. However, this process is time-consuming. To overcome this, a one-step DFSW technique was developed, where two tools simultaneously operate on both sides. This study aimed to investigate the impact of tool rotation speed on the fatigue crack growth rate of AA6061-T6 in one-step DFSW. One-step DFSW was performed at different upper and lower tool rotational speeds: 1500/900 rpm, 1500/1200 rpm, and 1500/1500 rpm. Tensile and fatigue crack growth tests were conducted on the joined specimens. The microstructure of the welded joint and the surface fractures resulting from the tests were analyzed using a scanning electron microscope (SEM). Results showed that the specimen welded at 1500/1500 rpm exhibited the lowest fatigue crack growth rate. The Paris constants (C and n) were determined as 4.348E-08 and 4.16, respectively. © 2024 The Authors