Microstructure, mechanical properties and stress dependence of corrosion resistance for MIG welded 7075 aluminum joint

As a competitive high-strength and high-hardness aluminum alloy in field of aerospace and rail transit, 7 series aluminum alloy and its welding performance have attracted attention. The microstructure and mechanical properties of single-side and double-side welded 7075 aluminum alloy joints were studied, and the corrosion resistance of the joints under different stresses in 3.5% NaCl solution was compared and analyzed. The result shows that, double-side MIG welding of 7075 aluminum alloy brings about more uniform microstructure and finer grain, but equivalent mechanical properties with the fracture at the weld in comparison with single-side MIG welding. The corrosion resistance of the near-weld zone for both single-side and double-side welding is higher than that of the weld and far away from the weld. In addition, double-side welding improves the corrosion resistance of the joint. Under the action of the applied stress, the steady-state passivation and activation processes of the specimen are destroyed, which results in the multiple anodic polarization actions in the process of potentiodynamic polarization. The corrosion process is thus affected by the coupling effects of stress, corrosion potential and other factors.