Mechanisms of fatigue crack initiation in metals: role of aqueous environments

Microarc Oxidation Coating Combined with Surface Pore-Sealing Treatment Enhances Corrosion Fatigue Performance of 7075-T7351 Al Alloy in Different Media

“…For the thicker coatings ( h = 20 μm), cracks in the inner coating are not filled well and electrochemical corrosion becomes severe so that the relative fatigue strength decreases within a certain range. In addition, the MAO coating with the pore-sealing treatment can enhance the corrosion fatigue performance of 7075-T7351 Al alloy, and its corrosion fatigue crack initiation can be attributed to three characteristics: (1) breakdown (corrugation and spalling) of MAO coating with pre-sealing treatment in high stress level, (2) forming pits and causing a stress concentration at the surface or interface, and (3) electrochemical attack on plastic deformation zones where the un-deformed zones act as a large cathode [ 22 , 25 , 28 , 29 ]. The evidence from the scanning electron microscopy analysis for these interpretations is given in Section 3.1 .…”

A microscopic study on the corrosion fatigue of ultra-fine grained and conventional Al–Mg alloy

“…In an aqueous environment, corrosion fatigue crack initiation which is associated with anodic dissolution can be attributed to up to three mechanisms [71][72][73][74]. These are: (1) pits that form and cause a stress concentration at the bottom of the formation (2) breakdown of the protective passive film on the metal with an associated chemical attack in the same location and (3) electrochemical attack to plastically deformed areas of a metal where the undeformed areas act as a large cathode.…”

Corrosion fatigue crack growth behavior of pipeline steel under underload-type variable amplitude loading schemes

“…(iii) Both time-and cycle-dependent processes, for example, may correspond to a maximum segregation of hydrogen to the crack tip that is both time and cycle dependent [6][7][8]. (iv) Time-dependent mechanical property attributes, such as room temperature creep [9][10][11] and high temperature creep [12], both of which could lead to crack tip blunting and mechanical damage to the crack tip materials.…”