The Fracture and Fatigue Properties of Anodised Aluminium Alloy

A Review on Anodizing of Aerospace Aluminum Alloys for Corrosion Protection

“…Anodic oxide films are not only prone to crack nucleation, but also an increase on the crack propagation rate has been reported. Two concurring mechanisms are proposed by Cree and Weidmann [106]: on the one hand the appearance of micro-cracks in the vicinity of the growing fatigue crack tip, which alter the growth characteristics by providing a path of least resistance. On the other hand, a lower plasticity of the oxide film compared to the underlying substrate, which reduces the closure of the crack.…”

“…It has been broadly reported that anodic oxide layers are detrimental to the fatigue properties of the underlying aluminum alloy [106][107][108][109][110][111]. The brittleness of the oxide film, typical of ceramic-like materials, compared to the substrate, makes the oxide film prone to crack nucleation.…”

“…The fatigue life is formed by two stages: the crack initiation period and the crack propagation period. The effect of the higher susceptibility to crack initiation by the presence of the anodic layer on fatigue properties can be understood from the fact that the crack initiation period accounts for up to 90% of the total fatigue life [106].…”

Coupled effects of substrate microstructure and sulphuric acid anodizing on fatigue life of a 2017A aluminum alloy

“…However, the improvement in the fatigue performance of these alloys could be severely impaired after the anodizing process. This discrepancy classically appears to be associated to the brittle and porous nature of the oxide layer [11][12][13], as well as the tensile residual stresses induced during the anodizing process [13][14][15]. Much of the available literature provides evidence that the reduction in fatigue life is not only due to the well-known brittle properties of the aluminum oxide, but also to the film thickness [15][16][17][18], type of anodizing process [14,15,18,19], surface pretreatment prior anodizing [20][21][22] and sealing treatment after anodizing [23,24].…”

Fatigue and fracture assessment of toxic metal replacement coatings for aerospace applications

“…However, through the strict adherence to standard industrial practise this effect can be reduced to more acceptable levels, although it may not be eliminated entirely. S-N data from a previous study [12] for Al2024:T4 aluminium alloy anodised using the BSAA process is shown below in Figure 2. In this instance a 22% reduction to fatigue strength was observed.…”