This research aims to investigate the effect of the exfoliation corrosion exposure time on the mechanical properties, the strength and elongation, of friction stir welded Al-Li alloy type 2195-T8. The exfoliation corrosion test was performed using the exfoliation corrosion (EXCO) solution, based on ASTM G34. The samples were exposed to different exposure times 24,48, 96, 192 and 384 h. The results showed that both the strength and elongation of the welded specimens-exposed to the exfoliation corrosion tests-were reduced. For example, the samples that were exposed to 384 h, their initial tensile strength and elongation were reduced by 13% and 17% respectively. The degradation process due to the exfoliation corrosion on the tensile strength was divided into three stages: fast (0-96 h: 443.7 MPa-416.3 MPa, the degraded rate was 0.29 MPa/h), steady (96-192 h: 416.3 MPa-413.4 MPa, the degraded rate was 0.03 MPa h −1 ) and medium rate MPa, the degraded rate was 0.14 MPa h −1 ). For the elongation, in general, the reduction was similar to the style of strength, but with different rates. The TEM images showed that this degradation was due to the dissolution of T 1 (Al 2 CuLi) and S′ (Al 2 CuMg) phase. Also, the corrosion products and their role of adherence on the surface of the tested specimens were investigated. An empirical equation p-t (mechanical properties-exposure time) was established to calculate the effect of exposure corrosion time on the performance of welded specimens.

Corrosion behavior of friction stir welded 2195-T8 Al-Li alloy has been investigated. Immersion corrosion test (NACE TM0169/G31-12a) and local electrochemical open circuit potential measurements were applied. The microstructure and precipitates evolution in different zones were investigated by SEM, stereoscope and TEM. The corrosion tests showed that the sequence of corrosion resistance of each area of the joint is: welding nugget zone (WNZ) > Base metal (BM) > heat affected zone (HAZ). The WNZ showed highest corrosion resistance due to the fine recrystallized grains, the dissolution of T1(Al2CuLi) phase, and the refined and evenly-distributed particles in this area. However, the HAZ had the lowest corrosion resistance as a result of the the intergranular precipitates, deleterious PFZ and the formation of galvanic corrosion couples among T1, θ´and PFZ.