Global anisotropic response of friction stir welded 2024 aluminum sheets

Abstract

This study investigated the global anisotropy of the friction stir welded (FSW) AA2024-T3 sheets. Different rotation speeds were used to generate welds. Uniaxial tensile tests were performed at various loading angles with respect to the welding direction. The deformation history during tensile tests was investigated by using the digital image correlation method to obtain r-values. Plastic anisotropy of the joints was modeled with Hill48, Yld89 and Yld2000-2d yield functions. The performance of these three yield criteria was evaluated by the comparison of theoretically calculated planar distributions of the uniaxial yield stress and the r-values with experimental data. Results show that the FSW joints show strong fracture and yield anisotropies. The yield stress is invariably the lowest in the diagonal direction and the highest in the rolling direction. The tensile strength and elongation are always the lowest at loading angles of 60° or 75°, rather than the commonly used 90°. The Yld2000-2d yield function can accurately describe the in-plane anisotropy of the joints compared to the other two. Rotation speed has a distinct effect on the mechanical properties of the FSW joints, resulting in evident changes in the shapes and magnitudes of the yield surfaces.