Stress Corrosion Behavior of 6061 Aluminum Alloy for Aviation under Constant Load

The effect of tensile stress on stress corrosion properties of aluminum alloy at different heat-treatment states (6061-T4 and 6061-T6) were studied by means of constant load full immersion corrosion tensile, fracture scanning and room temperature tensile methods. The results showed that in the coexistence of O₂ and Cl^-, the stress corrosion sensitivity of 6061-T4 aluminum alloy was very low, and the degradation of mechincal properties was mainly affected by the electrochemical corrosion of corrosive medium. The stress corrosion cracking sensitivity of the 6061-T6 aluminum alloy was higher than that of the 6061-T4 aluminum alloy, and the stress corrosion cracking tendency of the 6061-T6 aluminum alloy were mainly affected by corrosion and supplemented by mechanical factors. The surface corrosion areas of both aluminum alloys after stress corrosion were intergranular brittle fracture, the subsurfaces were quasi-dissociative fracture, and the centers were transgranular fracture.Under the simultaneous action of corrosive medium and stress, the corrosion of 6061-T4 aluminum alloy developed from pitting corrosion to intergranular corrosion, and finally became exfoliation corrosion as the stress increased. Pitting corrosion in 6061-T6 aluminum alloy was not obvious, but the depth of intergranular corrosion increased with stress.