Corrosion fatigue behavior of Ti-4Al-6Mo-2V-5Cr-2Zr alloy with different microstructures in 3.5 % NaCl solution

Ti-4Al-6Mo-2V-5Cr-2Zr alloy with different microstructures was prepared through two heat treatment processes (STA 1 and STA 2), and its corrosion fatigue behavior in a 3.5 % NaCl solution was investigated. STA 1 forms a hierarchical nanostructure (HN) containing coarse grain boundary α (GB α), primary α (α p ), and nanoscale secondary α (α s ) with significant elemental segregation. In contrast, STA 2 forms a lamellar structure (LM) composed of fine, needle-like α s with uniform element distribution. Results indicate that LM has better corrosion resistance, its passive film resistance (4.328 ×10 6 Ω·cm 2 ) is higher than that of HN (1.101 ×10 6 Ω·cm 2 , 6.9 nm). In a 3.5 % NaCl solution, STA 1 shows significant corrosion fatigue behavior, whereas STA 2 does not exhibit any signs of corrosion fatigue. The deformation in HN mainly occurs within the coarse α phase, and the high dislocation density can lead to localized stress concentrations, thereby damaging the passivation film and initiating corrosion fatigue cracks.