Microstructural influences on strengthening in a naturally aged and overaged Al–Cu–Li–Mg based alloy

Abstract

a b s t r a c tA combination of transmission electron microscopy, atom probe tomography and high-energy X-ray diffraction was employed to investigate the influence of local microstructural changes on strengthening in a commercial Al-Cu-Li-Mg based alloy, AA2198, in the stretched and naturally aged, and overaged states. Strengthening in the stretched and naturally aged temper was shown to be governed by a combination of Cu-Cu clusters, δ′/β′ phase and solution strengthening. This is in contrast to another report which suggests that strength in this temper is only due to Cu-rich clusters [B. Decreus, et al., Acta Mater., 61 (2013) 2207]. On the other hand, although large volume fractions of equilibrium phases such as T B , and θ were present in the overaged temper, its strengthening was largely governed by order hardening, which is the strengthening mechanism associated with the δ′/β′ phase. The δ′/β′ phase remained in the matrix even after extensive overaging.

Cu/Li Ratio on the Microstructure Evolution and Corrosion Behaviors of Al–xCu–yLi–Mg Alloys

“…The critical increase in the aforementioned mechanical properties owes largely to the precipitation of the disk shape of θ′ phase in {100} α and coarsening of the spherical δ′ phase [18]. In a welded joint section, the fusion zone possessed the best toughness performance, with a large number of needle-like intergranular T 1 phases, which verified that the T 1 phase played a significant role in improving the strength of the studied alloy [19]. Moreover, in a commercial AA2198-based alloy, the strength improvement via artificial aging (T8) was believed to be related to the θ′ phase, δ′ phase, and T 1 phase, and the aging temperature was also shown to have a critical influence on the morphology of the precipitates of the aging alloy [20].…”

Atomic-scale analysis of light alloys using atom probe tomography

“…For example, clusters of solute atoms can provide intrinsic strengthening upon their direct interaction with moving dislocations during deformation. 22–47 Solute clusters can also indirectly affect the material properties by cluster assisted nucleation of second phase, strengthening precipitates, 48,49 either intrinsically by having seeded the development of the aforementioned precipitates 50–53 or extrinsically by heterogeneous nucleation, where the solute species of the initial cluster are not strict constituents of the precipitate. 54–57 Atom-by-atom analysis afforded by APT data is also well suited to characterisation of short-range order (SRO), which is another characteristic of a solid solution that can affect the physical and mechanical properties of an alloy by, for example, the influence on phase transformation phenomena.…”

A high-temperature deformation model based on dislocation movement for wrought aluminium alloys

“…Wrought aluminium alloys that combine high strengthdensity ratios with excellent mechanical properties are widely used for aeronautical applications. [1][2][3][4] However, sheets of such wrought aluminium alloys show low formability at room temperature so that it is necessary to research into the high-temperature deformation behaviour of wrought aluminium alloys. Modelling and simulation are approaches which are widely used to study the high-temperature deformation behaviour and characterise microstructure evolution during the high-temperature deformation of a wrought aluminium alloy.…”