1993 Volume 42 Issue 475 Pages 405-411
Rotating bending fatigue tests have been conducted in a 3%NaCl solution using under-aged, peak-aged and over-aged materials of two aluminum-lithium alloys, 2090 and 8090. Detailed observations on corrosion pit, fatigue crack initiation and growth have been made, and the results obtained were compared with those of conventional aluminum alloys, 2024 and 7075. The corrosion fatigue strength of Al-Li alloys significantly reduced when compared with the fatigue strength in laboratory air, but was independent of aging condition. However, the peak-aged material showed relatively higher sensitivity to corrosion environment than the other aged materials. In comparison with 2024 and 7075 alloys, Al-Li alloys exhibited better corrosion fatigue strength. It was found that the corrosion fatigue process in Al-Li alloys consisted of corrosion pit initiation and growth, and fatigue crack initiation and subsequent growth. The density and size of corrosion pits in Al-Li alloys were much higher and smaller, respectively, than those in 2024 and 7075 alloys, and the configuration was extremely irregular. Corrosion fatigue cracks initiated from such corrossion pits and then grew. The crack growth of Al-Li alloy was enhanced in 3%NaCl solution at both low and high Kmax regions, due to corrosion dissolution and crack coalescence, respectively. Furthermore, the crack growth resistance of Al-Li alloys was almost the same as that of 7075 alloy, but was higher than that of 2024 alloy.