Effect of pre-deformation and artificial aging on fatigue life of 2198 Al-Li alloy

The effects of pre-deformation and artificial aging on fatigue life of 2198 Al-Li alloy were explored to further reveal its fatigue behavior and improve the damage tolerance. Fatigue life was investigated on 2198-T3 alloy after pre-deformation and aging treatments. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the fracture morphology, precipitation behavior, fatigue crack initiation and propagation. Results indicated that T 1 (Al 2 CuLi) phase dominated the strengthening of 2198-T3 alloy after the further aging. Pre-deformation increased the number of dislocations in the matrix, which provided favorable position for nucleation of T 1 . The precipitation of θ ′ (Al 2 Cu) and δ ′ (Al 3 Li) were inhibited. Also, the formation and coarsening of precipitate-free zone (PFZ) were effectively avoided in this condition. Dislocation density in the 2198 Al-Li alloy matrix increased with the amount of pre-deformation, leading to an increase in micro-crack defects on the surface and inside alloy. As a result, decreased fatigue life and an increased crack growth rate of the alloy were observed. Overall, 2198 Al-Li alloy had the best fatigue life and damage tolerance enhancement after it underwent 3% pre-deformation and was aged at 155 °C for 15 h.