Effect of tensile stress response for oxide films on the fatigue failure behavior of anodized AA6082 alloys

In recent times, the rapid rupture of oxide films caused due to their brittleness, porosity, residual tensile stress, and primary cracks has proven to be the main reason for the reduction in the fatigue limits of anodized aluminum alloys. However, the relationship between the cracking of the oxide films and the loading stress remains unclear. In this study, according to in-situ tensile test results, the critical stress when the film cracked on an anodized sample was determined to be 156.5 MPa, and a calculation method for determining the ultimate tensile strength of the film was proposed. Based on the critical stress, the tensile-tensile fatigue failure mechanisms above and below the critical stress (150 MPa and 170 MPa, respectively) were investigated. The results showed that when the tensile stress exceeded the critical stress, the fracture of the oxide film was the main reason for fatigue failure. However, when the tensile stress was lower than the critical stress, the stress concentration at the film-substrate interface was the leading cause of fatigue failure. The response of the oxide film to tensile stress is an important factor affecting the different fatigue failure mechanisms of anodized AA6082 alloys.