Investigating the environmental factors on corrosion and stress corrosion cracking behavior of Ti-6Al-3Nb-2Zr-1Mo alloy in simulated seawater

In this work, corrosion and stress corrosion cracking (SCC) behavior of Ti-6Al-3Nb-2Zr-1Mo welded joint in a multi-factor coupling simulated deep-sea environment were investigated. Through machine learning, micro-environment analysis and electrochemical tests of the crack tip, the intrinsic reason for SCC propagation was revealed. Results show corrosion and SCC are closely related to the passive current density, i_p. Among the environmental factors, pressure exerts higher weight factors for affecting i_p than dissolved oxygen and temperature, and the influence of microstructure is weak. As for SCC, both the environmental factors and microstructure influence localized Cl^- concentration and pH at the crack tip, therefore changing i_p and impacting SCC propagation. In addition, temperature can also affect capability for arresting SCC propagation in the constitutional phases. Microstructure leads to differences in SCC propagation behavior. The heat affected zone is more prone to SCC propagation than the base metal and the fusion zone.