The Influence of Deep Cryogenic and Uphill Quenching on AA7075 and AA6063 Alloys

This study investigates the implementation of a novel upward quenching process into the heat treatment cycles of the aluminum alloys ASTM 6063 and ASTM 7075. The method entails subjecting samples to cryogenic temperatures followed by heating after immersion in liquid nitrogen. The experiments analyzed the effects on microstructure, microhardness and mechanical properties. The findings demonstrate that cryogenic treatments facilitate a rapid diffusion rate of interstitial alloying elements. The study reveals that up-quenching induces substantial plastic deformation in ASTM 6063 samples, resulting in a thickness reduction of 43.3%. Conversely, ASTM 7075 exhibited a lower thickness reduction of 11.8% after uniaxial forming. While Uphill Quenching does not directly alter the microstructure of ASTM 6063, it does impact the microhardness of the ASTM 7075 alloy. Additionally, results indicate the ability of Uphill Quenching treatment to modify intermetallic morphology, aligning with the simulated effects of aging. The study indicates that up-tempering induces a more pronounced reduction in cold mechanically formed sections compared to samples formed solely in the solution-solid condition (T4). Overall, the article suggests that Uphill Quenching represents a viable alternative for the mechanical forming of aluminum alloys with high mechanical strength, offering advantageous mechanical and metallurgical characteristics.