Microstructures and adiabatic shear bands formed in steel plate under high rate impact

The projectiles of sintered tungsten alloy were fired directly on steels 45 and 30CrMnMo target plates. The microstructures near the perforation of steel 45 target plate can be divided,along radial direction as: melted and rapidly solidified layer, recrystallized fine-grained layer, deformed fine-grained layer, deformed layer and normal matrix. The adiabatic shear bands (ASBs) cannot be found in this intermediate strength steel. Observation of the microstructures around the radial direction of perforation of 30CrMnMo steel target plate shows that there is a melted and rapidly solidified layer on the surface of perforation, underneath there is a diffusing layer, and then a fine-grained layer appears as streamlines. Several kinds of ASBs are found in this high strength steel, they have different directions and widths, which are relative to the shock waves and reflect waves and the complex deformation-during penetration process. The deformations of projectiles are rather different when they impacted to different target plates. The projectile impacted on steel 45 target plate is tamped and exhausted slowly, while the projectile impacted on 30CrMnMo steel target plate is sheared and exhausted quickly. It indicates that the appearance of ASBs is relative to the strength and the strain of the materials under impact.