Two-Step Die Motion for Die Quenching of AA2024 Aluminum Alloy Billet on Servo Press

Abstract

The authors reported that die quenching of a cylindrical AA2024 aluminum alloy billet less than 9 mm in height was feasible on a servo press. However, it was also found that the reduction in height was limited less than 5% due to partial melting. In order to enhance the deformability in single operation, the two-step die motion is proposed. A cylindrical billet was heated to 823 K and transferred to the press. Then the billet was uniaxially compressed with Δh/h₀ = 5%, and further held between the dies for cooling. After sandwiching for 8 s, the billet with a height of h₁ = 7.6 mm was further compressed with a reduction in height (Δh/h₁) of 2 or 5% at lower temperature. The die quenching process with the two-step die motion leads to increase the total reduction in height to 10%. It is confirmed that super-saturated solid solution successfully formed at the 1st step is maintained in the 2nd step. It is found that the peak hardness of the two-step processed billet is higher than that of the one-step processed billet, and that the precipitation kinetics in artificial aging is accelerated by the two-step motion.