Microstructural evolution of 2519-T87 aluminum alloy obliquely impacted by projectile with velocity of 816 m/s

Target made of 2519-T87 aluminum alloy was obliquely impacted by a projectile. Microstructural evolution around the crater was investigated by optical microscopy (OM), transmission electron microscopy (TEM), and electron backscattered diffraction (EBSD). The micro-hardness distribution near the crater after impact was studied. The results indicate that at the entering stage, the amount of adiabatic shear band (ASB) is the most, and the precipitates are as fine as those of the target material; the micro-hardness is higher than that at the other stages. At the stable-running stage, the amount of ASB reduces as the micro-bands increase; the precipitates tend to coarsen, which leads to the decrease of the micro-hardness. At the leaving stage, there is a large amount of micro-bands; the precipitates are refined, and the micro-hardness is higher than that at the stable-running stage. The difference in the micro-hardness of the impact stages is due to work hardening and precipitate coarsening, which is caused by adiabatic temperature rise in the alloy.