Effect of prior corrosion state on the fatigue small cracking behaviour of 6151-T6 aluminum alloy

The purpose of this paper was to estimate the reliable effect of prior corrosion state on fatigue micro crack initiation and early stage propagation behaviour of aluminum alloy based on scanning electron microscopy (SEM) in situ observation. Results indicated that multi-cracks initiation occurred almost at the corrosion pits and the early stage of fatigue micro crack propagation behaviour can be described by KI/KII-mixed mode. The importance of crack-face interaction via crack-face corrosion pits interlocking/bridging was emphasised in the mixed mode. The fatigue crack growth rate in the corrosion states can be empirically expressed by the term of kσmaxna.

► Relationship of corrosion pit and fatigue crack is established based on SEM.
► An equivalent relationship between accelerated and natural corrosion is build up.
► Prior corrosion damage is crucial to the subsequent fatigue cracking behaviour.
► The prior corrosion fatigue crack growth rate is expressed by the term of kσmaxna.
► Corrosion states such as SC15, are defined based on corrosion spectrum.