The role of grain structure characteristics on the localised corrosion feature in the 1445 Al-Cu-Li alloy

Highlights: • The corrosion behaviors of aged 1445 Al-Li alloy includes IGC, SIGC and SGC, not uniform to that of the normal Al-Li alloy. • The IGC is due to the T₁ phase on the high grain boundary. The SIGC is attributed to S′ phase on the low grain boundary. • The SGC is linked to copper-rich nanoparticles, located on dislocation bands of deformation with high grain stored energy. • In the zone of un-recrystallize grains, the corrosion appeared on the prioritization of the specific grain orientation. -- Abstract: The corrosion behavior of the 1445 aged alloy was studied by analysis of microstructure characteristics and grain structure characteristics achieved from TEM, STEM, and EBSD. Three corrosion modes including intergranular corrosion (IGC), sub-intergranular corrosion (SIGC), and sub-intragranular corrosion (SGC) were found in the aged samples. In contrast with the conventional Al-Cu-Li alloy, the increased corrosion resistance was derived from the lower chemical potential difference between δ′ phase in matrix and S′ phase at GBs. The grain stored energy can significantly affect the SGC especially under a specific grain orientation thus the corrosion resistance of deformed grains can be increased.