Microstructure and ratcheting behavior of 6061 aluminum alloy laser-MIG hybrid welding joint

In this paper, 6061-T6 aluminum alloy was welded by laser-MIG hybrid welding. The microstructures of the upper part of the weld center, the lower part and the edge of the weld near the fusion line in the welded joint were analyzed. The hardness and mechanical properties of welded joints were analyzed in detail. The ratchet strain of 6061 aluminum alloy welded joints was tested, and the asymmetric stress control method was used to test the ratchet strain of 6061 aluminum alloy welded joints. The results show that ratcheting strain increases with the increase of average stress and stress amplitude, and has the characteristics of cyclic softening first and then hardening. The degree of hardening increases with the increase of the maximum cyclic stress. Cyclic hardening is mainly caused by the uninterrupted dislocations in the process of cycling. The accumulation of ratchet strain results in plastic damage of materials. Pre-ratcheting can improve the tensile properties of welded joints by 6.49% and 97.7% yield strength, which is mainly attributed to cyclic hardening caused by ratcheting strain.