Strengthening of A2024 alloy by high-pressure torsion and subsequent aging

An age-hardenable A2024 alloy is processed by high-pressure torsion (HPT) for grain refinement and further aged for fine precipitation. The HPT is conducted under an applied pressure of 6 GPa for 0.75, 1 and 5 turns with a rotation speed of 1 rpm at room temperature and this results in a significant grain size reduction to a grain size of ~ 240 ± 80 nm. The hardness sharply increases with imposing strain at an early stage but level off after 5 turns. Further aging at temperatures of 373 K and 423 K leads to extra hardening above the elevated hardness of the HPT-processed condition. Components contributing to the strengthening were evaluated in terms of grain refinement and fine precipitation including the contributions from dislocation accumulation and solid solution. In this study, a conclusion is reached such that simultaneous strengthening due to grain refinement and fine precipitation is achieved by application of HPT processing and subsequent aging.