Damage of Al 2024 alloy due to sequential exposure to fatigue, corrosion and fatigue

Fatigue and corrosion are two major concerns of aging aircraft research. Metal corrosion and fatigue act synergistically in various ways. They may be present separately or simultaneously. In this study Al 2024-T3 alloy was intermittently subjected to sequential corrosion and fatigue processes. Specimens were first subjected to various degrees of fatigue damage in air, then immersed in a corrosive solution for a fixed amount of time, and subsequently further fatigued in air to failure. The results are compared with those subjected to fatigue in air, and to corrosion then fatigue in air. We find that the total fatigue life (sum of fatigue cycles before and after corrosion) exceeds that of the virgin samples, provided that the initial fatigue cycle has consumed more than half of life solely fatigued in air. It is believed that the blunting of microcracks and the removal of other surface damage, such as intrusions/extrusions created at the initial stage of fatigue, are the major reasons for this increased fatigue life.