Effect of Anodic Oxide Film on Fatigue Behaviour of Magnesium Alloys in Laboratory Air and Demineralized Water

Abstract

This paper describes the effect of anodic oxide film on fatigue behaviour of wrought magnesium alloys. Rotating bending fatigue tests have been performed using smooth specimens with anodic oxide films in laboratory air and demineralized water. Two different anodic oxide films, Mg-Hard and Mg-Light, were evaluated, in which both films had the same thickness of 30 μm, but the former had considerably higher hardness than the latter. In laboratory air, the fatigue strength of the anodized specimens with Mg-Hard was nearly the same as, or slightly higher than, that of the bare or untreated specimens, while the anodized specimens with Mg-Light exhibited higher fatigue strength than the bare specimens. In demineralized water, the fatigue strengths of both anodized specimens were the same as these of the bare specimens, indicating no improvement of corrosion fatigue strength by the anodic oxide films. This was because pores and crackings preexisted within the anodic oxide films acted as penetration path of the solution, thus similar corrosion fatigue process to the bare specimens took place underneath the anodic oxide films.