Corrosion Behavior of the Al-Li-Cu-Mg Alloy.

The localized corrosion behavior of the Al-Li-Cu-Mg alloy 8090-T651 (25 mm thick plate) was investigated using salt spray tests, the EXCO test and tests according to the MIL-H-6088F specification. These accelerated laboratory tests indicate that the material is susceptible to intergranular and exfoliation corrosion. The stress corrosion cracking behavior was studied under constant load, constant deformation and slow strain rate conditions. The material was found to be resistant to stress corrosion cracking in the long transverse direction. In the short transverse direction a threshold stress below 50 MPa was determined. The same values were measured for the conventional alloys 2014-T351 and 2024-T351. The fracture surfaces of specimens which failed due to stress corrosion cracking were examined using a scanning electron microscope. Fractographic features attributed to corrosion are discussed.