Age-hardening of an Al–Li–Cu–Mg alloy (2091) processed by high-pressure torsion

This research presents the successful strengthening of an Al–Li–Cu–Mg alloy (2091) through the simultaneous use of grain refinement and age hardening. Following solid–solution treatment, the alloy was processed by high-pressure torsion (HPT) at room temperature and the grain size was refined to ∼140 nm. The Vickers microhardness increased with increasing strain, and saturated to a constant level of 225 Hv. A further increase in the hardness to ∼275 Hv was achieved by aging the HPT-processed alloy at 100 °C and 150 °C. Bending tests for the samples treated using the peak aging conditions demonstrated that the stress was significantly increased while considerable ductility was retained. Transmission electron microscopy revealed that the small grains are well retained even after prolonged aging, and the precipitation of fine δ′ particles occurred within the small grains, which confirms that simultaneous strengthening from grain refinement and age hardening is feasible in this alloy.