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

Abstract

Abstract 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 T1 (Al2CuLi) 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 T1. The precipitation of θ′ (Al2Cu) and δ′ (Al3Li) 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.