Distinct microstructural contributions to intergranular corrosion and stress corrosion cracking in aged 2050 Al–Li alloy

Aging-induced precipitation strongly affects the corrosion behavior of Al–Li alloys, yet intergranular corrosion (IGC) and stress corrosion cracking (SCC) may respond differently to changes in precipitation and grain-boundary microstructure. In this work, the precipitation behavior, grain-boundary microchemistry, electrochemical response, corrosion-induced hydrogen absorption, IGC susceptibility, and SCC behavior of 2050 Al–Li alloy subjected to T6, T8, and double aging treatments were systematically investigated. T8 aging promoted the formation of fine and densely distributed intragranular T 1 precipitates through deformation-assisted nucleation, whereas double aging produced coarser intragranular T 1 precipitates and more discontinuous grain-boundary precipitation. The maximum IGC depth decreased from 190.08 μm under T6 aging to 113.12 μm under double aging, indicating a marked improvement in IGC resistance. In contrast, the SCC susceptibility index increased from 10.11% under T6 aging to 19.15% under double aging, while the T8 alloy showed intermediate behavior. The results suggest that IGC propagation is mainly associated with the continuity of the electrochemically active grain-boundary path formed by grain-boundary precipitates and adjacent solute redistribution. By comparison, SCC is influenced by the combined effects of interfacial electrochemical behavior, stress-assisted localized dissolution, and hydrogen-related processes. Consequently, the IGC and SCC resistance rankings show opposite trends under the investigated aging conditions.