Effect of Cryogenic Treatment on the Mechanical Anisotropy and Microstructure of 2024 Aluminum Alloy

Uniaxial tensile tests were conducted to investigate the mechanical anisotropy of rolled 2024 aluminum alloy sheets subjected to different cryogenic treatment durations along the rolling direction (0°), diagonal direction (45°), and transverse direction (90°). The experimental results indicate that the mechanical properties of the rolled 2024 aluminum alloy are strongly dependent on the treatment process and exhibit pronounced anisotropy. With increasing cryogenic treatment time, the yield strength first increases and then tends to stabilize. The optimal combination of mechanical properties is achieved after cryogenic treatment for 16 h, with the yield strength increasing to 385–390 MPa. Cryogenic treatment has no significant effect on the grain morphology of the matrix, but promotes dislocation multiplication and a more uniform distribution of precipitation features. The anisotropy analysis shows that the yield strength in the 45° direction is consistently lower than that in the 0° and 90° directions. The in-plane anisotropy parameter (IPA) decreased from 4.8% in the condition without deep cryogenic treatment to 3.0% after 4 h of cryogenic treatment, followed by an increase to 6.7% after 24 h. This result indicates that short-term cryogenic treatment can effectively reduce the in-plane anisotropy of the 2024 aluminum alloy.