Influence of plastic deformation and Cu/Mg ratio on the strengthening mechanisms and precipitation behavior of AA2024 aluminum alloys

The strengthening mechanisms and precipitation behavior in AA2024 alloys with different Cu/Mg ratios (3.18 and 2.48) and different levels of plastic deformation (5 and 15%) were studied by X-ray diffraction, transmission electron microscopy and Vickers microhardness measurements. Results demonstrate that hardening depends significantly on the interaction of different strengthening mechanisms such as solid-solution, strain hardening and precipitation. Hardness is mostly influenced by precipitation, which in turn is modified by plastic deformation and the Cu/Mg ratio. Modification of Cu and Mg content as well as plastic deformation affect the precipitation behavior of the Al2CuMg (S) phase, since these lead to significant changes in size and numeric density of the S precipitates. A higher number density and a smaller size of S precipitates are obtained in the alloy with lower Cu/Mg ratio and 15% of thickness reduction.