Hardening and defect structures in thermomechanically processed Al-2.5Cu-1.5Mg (wt.%) alloy

The effect of thermomechanical processing on the hardening and defect structure of an Al-2.5Cu-1.5Mg (wt.%) alloy has been examined using hardness measurements and transmission electron microscopy. The rapid age-hardening reaction, which is known to contribute ∼70% of the total hardening response of the alloy, was found to be higher than that arising from up to 3% rolling. Comparisons between the hardening arising from a processing sequence involving ageing/deformation/ageing were shown to be slightly higher than those where deformation immediately follows after the quench. The defect structure produced from these two processing routes was distinctly different such that dislocation loops and helices predominate in samples aged prior to deformation. Alternatively, the dislocation tangles introduced when deformation is the initial step after quenching persist throughout subsequent ageing and restrict the growth of loops and helices.