Low-Cycle Corrosion Fatigue Deformation Mechanism for an α+β Ti-6Al-4V-0.55Fe Alloy

Titanium alloys with high strength and good corrosion resistance have become one of the critical bearing structural materials in marine engineering. But in service, corrosion fatigue would occur under the synergetic action of cyclic external load and corrosion environment, threatening the safety of components. In this study, compared with low-cycle fatigue in laboratory air, the low-cycle corrosion fatigue deformation mechanism and fracture characteristic of the Ti-6Al-4V-0.55Fe alloy were investigated in 3.5% NaCl corrosion solution under selected stress amplitudes. The results showed that under low stress amplitude, corrosion fatigue was determined by fatigue damage and corrosion damage, causing a reduction in fatigue life. The local stress concentration caused by corrosion pits and dislocations pile-up accelerated the initiation of fatigue cracks, and other corrosion behavior including crevice corrosion promoted fatigue crack propagation; the corrosion solution increased the surface damage. While under high stress amplitude, due to the short contact time between the sample and solution and higher applied stress, the fatigue life is determined by fatigue damage caused by multiple slips.