Pre-Deformation-Assisted Retrogression and Re-Aging Treatment for Achieving Strength–Corrosion Synergy in 2195 Al–Cu–Li Alloy: Insights into Cu Redistribution and Grain Boundary Evolution

Al–Cu–Li alloys face an intrinsic trade-off between precipitation strengthening and intergranular corrosion susceptibility. This trade-off restricts the simultaneous improvement of their strength and corrosion resistance. In this work, a pre-deformation-assisted retrogression and re-aging (RRA) strategy was developed to regulate Cu redistribution and balance the mechanical and corrosion properties of 2195 Al–Cu–Li alloy. The results show that short-time retrogression maintains effective strengthening while limiting Cu depletion near grain boundaries, thereby achieving an improved strength–corrosion balance under the investigated processing conditions. The RRA-5 min sample exhibited the optimum performance, with a yield strength of 533 MPa, ultimate tensile strength of 562.6 MPa, and polarization resistance of 19,605 Ω·cm2. Prolonged retrogression promoted Cu redistribution toward grain boundaries, potentially promoting precipitate-free zone (PFZ) evolution, electrochemical heterogeneity, and intergranular corrosion susceptibility. XPS analysis revealed that the corrosion film consisted mainly of Al oxides and hydroxides, Li- and Mg-containing compounds, and Cu-enriched species, suggesting selective dissolution and corrosion film reconstruction during exposure. The coupled Cu diffusion–grain boundary absorption model predicted the evolution tendency of PFZ widening with increasing retrogression time, which was consistent with the experimental trend. This study provides insights into the regulation of Cu redistribution through RRA processing for achieving strength–corrosion synergy in aerospace Al–Cu–Li alloys under the present processing conditions.