Effect of pre-straining on the aging behavior and mechanical properties of an Al–Cu–Mg–Ag alloy

The effects of cold deformation prior to aging on the precipitation behavior, microstructure and mechanical properties of an Al–5.6Cu–0.72 Mg–0.5Ag–0.32Mn–0.17Sc–0.12Zr (in wt%) alloy were investigated. Pre-straining disrupts the formation of Mg–Ag co-clusters, modifying the normal precipitation sequence. A strong increase in the dislocation density by a factor of 100 leads to a ~40% decrease in the number density, NV, of the Ω-phase at pre-strains of ε≥1% (ε≥0.01). The aspect ratios of the platelets in this phase increased from ~21 to ~42 after a negligible pre-strain of ≤1% (ε≤0.01) and further decreased to ~25 in the pre-strain interval of 1–80% (ε~0.01–1.61). In addition, the nucleation of the Cu-rich θ′-phase occurs on dislocations. The heterogeneous nucleation of the thick Ω-phase particles with low aspect ratios (~12) and equiaxed particles of S-phase with dimensions ≤5 nm on the deformation-induced boundaries was found. After peak aging, the yield stress (YS) and ultimate tensile strength (UTS) increased from 478±4 MPa and 522±8 MPa for the as-quenched alloy to 516±4 MPa and 568±6 MPa in the longitudinal and 554±5 MPa and 601±3 MPa in the transversal directions, respectively, for the alloy subjected to pre-straining with a rolling reduction of 80% (ε~1.61). Cold rolling prior to aging induces the anisotropy in mechanical behavior through the formation of deformation bands.