The effect of anodized coating on fatigue strength of aluminum alloys

Abstract

As a study in a series to investigate the effect of anodized coating on fatigue strength of aluminum alloys, repeated tensile fatigue test was conducted in laboratory air and at room temperature under the stress ratio of 0.01 using smooth plate specimen of A2014-T6 and A6151-T6 with anodized film thickness of 3 μm. Fatigue strength of the anodized specimens decreased by 20-30% as compared with those of uncoated one. Decrease of fatigue strength depended on static strength of the tested materials. The fracture of anodized coating film occurred at the critical strain formed by the accumulation of plastic deformation of substrate metal at an early stage of repeated tensile fatigue process and crack was induced in the substrate at the flaw of the anodized film. It was recognized that fatigue life of anodized specimens was quantitatively evaluated by the consideration of cyclic stress-strain response and strain-life fatigue behavior.