本實驗係以2024-T3鋁合金為基材，在實驗室中的人造鏽蝕環境下以交互浸潤鏽蝕法（Alternative Immersion Corrosion Process），對2024-T3鋁合金試片在3.5％的氯化鈉溶液中分別進行7、21及42天的連續浸潤-風乾的鏽蝕程序。在試片完成鏽蝕程序後，施以不同程度的應力進行疲勞試驗，以獲得在不同鏽蝕天數下的應力－疲勞壽命曲線。最後再以電子顯微鏡進行材料斷裂面的孔蝕深度及面積的觀測，藉此找出鏽蝕程度與疲勞壽命間的關係。
實驗結果顯示試片的疲勞壽命隨鏽蝕時間的增加而降低，以在25 ksi循環應力下的結果為例，經7、21及42天浸潤鏽蝕之試片的疲勞壽命分別為86,100、67,200及56,200次循環；後者的疲勞壽命相較於前二者的疲勞壽命衰減的幅度分別約為35%及16%。材料的疲勞壽命係受到鏽蝕深度、孔蝕前端形狀、鏽蝕造成的截面積損失、多區域疲勞裂紋發展及承受應力等各項因素間交互影響而呈現衰減趨勢。

In this study, the 2024-T3 aluminum alloy was used as base material. By using alternative immersion corrosion process with an artificial corrosive environment in laboratory, 2024-T3 aluminum alloy specimens were subjected to continual immersion-dry process in 3.5% sodium chloride solution for 7, 21, and 42 days, respectively. After the corrosion process, the specimens were then subjected to fatigue test at different stress levels and S-N curves of material under different corrosion level were obtained. In addition, through the use of Scanning Electronic Microscope, the depth and dimension of pitting on the fracture surface of specimens were observed.
The experiment results show that the fatigue lives of specimens reduce as the exposure time increases. For example, at the stress level of 25 ksi, fatigue lives of specimens subjected to immersion-dry process for 42 days reduce approximately by 35% and 16%, respectively, as compared to those subjected to processes for 7 and 21 days. Furthermore, fatigue life of material was affected by the combined effects of pit depth, leading edge shape of pit, loss of cross-section, multiple fatigue cracks growth and stress.

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