Mechanistic investigation of hydrostatic pressure effects on stress corrosion cracking in Ti-6Al-4V welded joints

The reliability of titanium alloy welded joints is critical to the service safety of deep-sea engineering systems. The welding thermal cycle generates complex microstructures in Ti-6Al-4V, resulting in pronounced mechanical and electrochemical heterogeneity across joint regions. Herein, in-situ electrochemical testing was conducted to investigate stress corrosion cracking (SCC) behavior in distinct weld zones under hydrostatic pressure. Results reveal that hydrostatic pressure accelerates electrochemical reactions and enhances the SCC susceptibility—most severely in the heat-affected zone. This heightened vulnerability stems from the transformed β phase and lamellar secondary α phase, which promotes strain localization and impairs repassivation capability. This work presents the evidence of region-dependent-SCC susceptibility in Ti-6Al-4V welds under hydrostatic pressure, offering essential experimental insights for the safety assessment and welding optimization in deep-sea titanium structures.