摘要
Multiple ballistic impacts are carried out on a 2024-T4 aluminum alloy by spherical steel projectiles(5-mm diameter)at~400 m s^(-1),to investigate its dynamic deformation and damage.The ballistic impact process is captured with high-speed photography.Postmortem samples are characterized with optical imaging,three-dimensional laser scanning,microhardness testing and electron backscatter diffraction.With increasing number of impacts,crater diameter increases slightly,but crater depth and crater volume increase significantly,and strain accumulation leads to microhardness increase overall.Crater parameters all follow power-law relations with the number of impacts.Twin-like deformation bands and macroscopic deformation twins are produced by impact as a result of spontaneous dislocation self-pinning under high strain rate,large shear deformation.Under multiple impacts,shear strain accumulation in the arc-shaped region of the crater induces deformation twinning when it exceeds a critical value(~1.1-1.6).It is highly possible that the deformation twins are related to deformation bands,since they both share one set of the{111}pole with the initial matrix grain.A finite element method model is optimized to reproduce experimental observations and interpret deformation mechanisms.
基金
supported by the Scientific Challenge Project of China(Grant No.TZ2018001)
the National Natural Science Foundation of China(Grant Nos.11627901,11802252)
the Science and Technology Program of Sichuan Province(Grant No.2020YFG0415)。
