Dynamic fracture properties of 2024-T3 and 7075-T6 aluminum friction stir welded joints with different welding parameters

Friction stir welding (FSW) is widely used in the aerospace structure. The FSWed joints are often exposed to dynamic loads during their service applications. So, it is important to study the dynamic response of aluminum welded joints. This paper aims to investigate the effect of welding parameters on rate-dependent dynamic tensile properties of 2024-T3 and 7075-T6 aluminum FSWed joints. Samples in different welded zones were cut along the welding direction and tested by the tensile split Hopkinson bar. It is observed that the yield stresses of 2024 and 7075 heat affected zone (HAZ) are higher than that of the stirred zone (SZ) and the thermo-mechanically affected zone (TMAZ). Tensile ductility of 2024 increases with the rotational speed. However, the effect of different welding speeds on 7075 flow stress and fracture strain is not obvious. The mechanical response of 2024 and 7075 is not sensitive to the different dynamic strain rates in this case. The SEM fracture morphologies of the stirred zone present fine and equiaxed particles with plenty of different size dimples. The heat affected zone and the thermo-mechanically affected zone exhibit plenty of large and different size dimples, and the listed features indicate the typical ductile and transgranular fracture. Fracture surfaces of different welding parameter samples demonstrate that, compared with the same welded zone, finer dimples and uniform size particles can enhance the strength and ductility.