Effect of Prerecovery Annealing on Microstructure and Mechanical Properties of AA8021 Aluminum Alloy used for Aluminum Plastic Films

Abstract

In the present work, the effect of prerecovery annealing on microstructural evolution and mechanical properties of AA8021 aluminum alloy is reported. It is found that the grain refinement for sample recovery annealing at 150 °C is limited, and prolonged holding time deteriorates its microstructural uniformity, leading to a decrease in mechanical properties. Also, compared to annealing at 420 °C × 3 h after direct rolling to 0.5 mm, prerecovery annealing at 150 °C and 280 °C with a thickness of 1 mm can moderately refine the grain size and significantly improve the elongation, respectively, which is found closely related to the recrystallization behaviors. It is determined that the AA8021 alloy reaches a nearly complete recrystallization state after 6 h high-temperature recovery at 280 °C, which is found primarily through continuous recrystallization involving subgrain rotation and subgrain boundary coalescence. Further, the enhanced elongation presented in the plate annealed at 280 °C × 6 h (1 mm) + 420 °C × 3 h (0.5 mm) is proved to be mainly attributed to the reduction in grain size and increased recrystallization.