Corrosion mechanism and fatigue behavior of aluminum alloy with high silicon content

The corrosion and corrosion-assisted fatigue life degradation behaviors of Al–8Si alloy is investigated. The test results show that galvanic cells are formed in the inter-dendrites due to high Si concentration, leading to pitting corrosion. The Al₂Cu phase and the Si-rich phase precipitate at the grain boundaries in the inter-dendrites, among which the Al₂Cu phase is the most critical factor leading to intergranular corrosion. Subsequently, intergranular corrosion gradually develops into intragranular corrosion attributed to the higher dislocation energy in fine-grained Al grains. Additionally, it is found by comparing the corrosion potential and corrosion rate that high Si concentration would cause the decrease in corrosion resistance. Finally, the fatigue test results show that the corrosion could reduce fatigue life of Al–8Si alloy by 79.77% on average. Therefore, the corrosion-induced fatigue life degradation is very worth to be considered in structures.