Effect of Cyclic Heat Treatment on the Mechanical Properties and Microstructure of Al 6061 Alloy

This study investigates the influence of different cyclic heat‐treatment schedules on the mechanical behavior and microstructural evolution of Al 6061 alloy. Five identically sourced plates were subjected to controlled variations in quenching rate, aging temperature, and cooling conditions to establish a consistent microstructure–property relationship. The heat‐treatment routes included water quenching, furnace cooling, single‐stage aging, and multistage aging sequences, allowing a systematic comparison of precipitation responses. Tensile tests, hardness measurements, and optical microscopy were performed to assess the effect of thermal history on yield strength, ductility, and precipitate morphology. The results reveal that water quenching followed by aging at 200°C produces the finest Mg 2 Si precipitate dispersion, yielding the highest hardness and improved yield strength, though with reduced ductility. In contrast, multistage aging combined with furnace cooling leads to precipitate coarsening, resulting in lower strength but enhanced ductility. Among all conditions, the furnace‐cooled, 200°C‐aged sample exhibited the most favorable strength–ductility balance, demonstrating the ability of controlled slow cooling and single‐step aging to restore fine precipitation and improve mechanical stability. Fractography analysis of fractured specimens further revealed the correlation between precipitate distribution and fracture behavior, confirming the transition from strength‐dominated to ductility‐dominated failure modes under different heat‐treatment conditions. Overall, the study highlights the critical role of cooling rate and aging sequence in tailoring mechanical performance and offers an alternative, industrially viable route for optimizing Al 6061 alloy properties.