Quasi-static behavior of notched Ti-6Al-4V specimens in water-methanol solution

The adoption of Ti-6Al-4V titanium alloy is widespread in advanced engineering fields, such as the aerospace, automotive, and maritime sectors, due to its remarkable mechanical characteristics and proven corrosion resistance. However, literature studies and field failures have underlined that the Ti-6Al-4V is susceptible to the stress corrosion cracking (SCC) and the corrosion fatigue phenomena in methanol-water solutions. Although several studies focused on the SCC behavior of this particular titanium alloy, recent corrosion fatigue experiments (R=0.1) on Ti-6Al-4V specimens in a water-methanol environment have highlighted a sensible decrease in maximum applied stress of up to 50% and a high sensitivity even to low methanol concentrations. In the present work, an experimental quasi-static SCC test campaign in water-methanol mixture at different concentrations has been conducted on flat dogbone Ti-6Al-4V specimens. The results have been compared with recent corrosion fatigue experiments to characterize the different damage mechanisms at play and decouple mechanical and chemical driving forces. The micromechanical behavior of the material has been analyzed, highlighting the role of the microstructure in the SCC mechanism. Failure surfaces have been investigated with scanning electron and optical microscopy.