| Aviation metal structures often face the combined effect of Marine corrosion environment and repeated impact loads during service, which leads to corrosion damage on the material surface and significantly deteriorates its impact fatigue performance. In order to explore this phenomenon in depth, this paper systematically studied the impact fatigue life of AerMet100 steel and TC18 titanium alloy, the key structural materials in the aviation field, under different duration of neutral salt spray pre-corrosion. The impact of corrosion duration on the impact fatigue life of two types of notched three-point bending specimens and the damage mechanism were systematically revealed by the neutral salt spray pre-corrosion test, the dropping hammer impact fatigue life measurement test and the scanning electron microscope (SEM) characterization technology. The results show: With the increase of salt spray corrosion time, the fatigue life of U/V-90° notched specimens of AerMet100 steel and TC18 titanium alloy U-notched specimens show a nearly linear decay trend, and the fatigue life of AerMet100 steel decreases to about 50% of that of non-corroded specimens after 240 hours of corrosion. However, the U-notched specimen of TC18 titanium alloy decreased to about 50% of the uncorroded specimen after 480 hours of corrosion. In contrast, the fatigue life of the V-90° notched specimen of TC18 titanium alloy is mainly affected by the stress state rather than the corrosion damage due to the high stress triaxial degree at the notch location. In addition, the SEM results show that with the extension of corrosion time, the number of corrosion products and pitting pits on the surface of AerMet100 steel samples increases significantly, accompanied by surface cracking, which promotes the initiation and propagation of fatigue cracks. Due to the shielding effect of the surface passivating film on the corrosive medium, the TC18 titanium alloy effectively prevents the in-depth erosion of the corrosive medium, limits the propagation path of the crack, and maintains a high fatigue life. |
