Analysis of Multi-zone Fatigue Crack Growth Behavior of Friction Stir Welded 5083 Aluminum Alloy

Bobbin tool friction stir welding is an expanded technology of friction stir welding, which has broad application prospects. In this study, an analysis of the microstructure and hardness, tensile performance, and crack growth behavior of a 12-mm-thick 5083 aluminum-alloy bobbin tool friction stir welding joint were carried out for different zones. The results show that the tensile strength of NZ can reach 95% of BM, while the tensile strength of HAZ is only 73% of BM; the elongation of NZ is 97% of BM, and the elongation of HAZ is only 47% of BM. The mechanical properties of 5083 aluminum alloy decreased after welding. For a specimen with a pre-crack vertical to the weld, when the crack propagates from the base material into the weld, the growth rate is significantly accelerated due to poor weld performance. The specimen with a pre-crack near the heat-affected zone has the fastest crack growth rate, and for the specimen with a pre-crack inside the weld nugget, the growth rate is between the other two specimens.