Influence of post-weld explosive treatment on low cycle fatigue of AA7075-T651 friction stir welded joint

In this investigation the friction stir welded joint of 5 mm thick AA7075-T651 alloy have been subjected to the post-weld explosive treatment. To assess the influence of the proposed treatment on the joint properties, a comprehensive analysis was conducted, including microstructural examination, microhardness testing, static tensile tests, low-cycle fatigue testing, and fracture surface observations. The strain amplitudes of 0.35 %, 0.4 %, 0.5 %, and 0.6 % with asymmetry coefficient R = 0.1, were used for the examined samples. It was concluded that the explosively treated FSW joints are characterized by a lower amplitude of plastic deformation, a reduced number of cycles to failure and show a tendency for cyclic softening. The differences in the fatigue crack propagation primarily concern the initiation area of the crack near the hardened surface. Explosive treatment did not influence the location of material decohesion, which occurs in the low-hardness zone.