Combined Effect of Pre-Strain at Elevated Temperature and Pre-Aging on Aging Strength and Microstructures of AA6082

Abstract

With the increasingly serious energy and environmental issues, aluminum alloys are becoming increasingly desirable for transportation facilities due to their high specific strength. Their low formability results in the difficulty of forming complex-shaped panels and bodies. Hot stamping is a new technology developed to address this formability challenge by applying plastic deformation to the heated aluminum alloy sheet at the solution heat treatment temperature. The stamped panels gain high strength via the sequent aging treatment. Different panels, even different regions on the same panel, are subjected to different forming strains. The present paper is focused on the experimentally investigating the effects of the pre-strain at elevated temperature and pre-aging on the mechanical behavior and microstructures of AA6082 after the natural aging, paint-bake treatment, and artificial aging. Sample sheets of AA6082-T6 were pre-strained by uniaxial tension at different levels of strain, and then subjected to the pre-aging, natural aging, paint-bake treatment or artificial aging, respectively. The yield strength, tensile strength and elongation of post-aged samples were gained via the standard uniaxial tensile tests. The results show that both of the pre-strain at elevated temperature and pre-aging suppress the natural aging of AA6082. Pre-strain at elevated temperature induces weak bake softening, and has a detrimental effect on the artificial aging strengthening, while the sequent pre-aging could compensate the strength decrease.