Ballistic impact experiments and modeling on impact cratering, deformation and damage of 2024-T4 aluminum alloy

Single-shot ballistic impact experiments are conducted on a 2024-T4 aluminum alloy (2024Al-T4) using spherical projectiles, to investigate the effects of impact velocities (~ 100 to 2000 m s(-1)) on impact cratering, deformation and damage. High-speed photography is applied to capture the impact processes. Impact-recovered targets are characterized using optical imaging, three-dimensional laser scanning, metallography, scanning electron microscopy and electron backscatter diffraction. With increasing impact velocity, the normalized crater depth follows the Poncelet model, and the normalized crater volume, a power-law relation, over the entire impact velocity range. Meanwhile, deformation and damage mechanisms undergo changes sequentially from micro deformation banding, shear banding, macroscopic deformation twining, microcracking, to melting. Macroscopic deformation twins are observed for the first time in high stacking-fault-energy materials including Al alloys under single-shot impact. Compared to multiple-shot impact cases, equivalent single-shot impact cases with the same total impact energy show similar crater parameters, but different microstructures (shear bands, cracks and deformation twins). Numerical simulations based on the Johnson-Cook model are established for impact penetration of 2024Al-T4 alloys, and simulations with this model are consistent with the experimental observations.