Adiabatic shear bands produced in a metallic armor, after dynamic compression with a Hopkinson pressure bar

Abstract

A Brazilian high hardness armor (HHA) steel was, for the first time dynamically tested and microstructurally analyzed for the occurrence of shear bands. The HHA was initially quenched at 910 °C for 10 min and tempered at 310, 425 and 610 °C for 1 h to produce different microstructures as well as phases and precipitates. After characterizing the microstructures, a dynamic compression test on a Hopkinson bar was performed on special samples to simulate high deformation rate in a ballistic impact. Then, a search for adiabatic shear bands, using scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) was performed on the impacted samples. The transformed shear bands generated were characterized by X-ray diffraction (XRD) and electron backscattering diffraction (EBSD). The results showed that the microstructure generated in the tempering heat treatment at 310 °C is the most susceptible to the appearance of shear bands. In addition, it can be indicated that the formation of these band is related to a possible dynamic recrystallization mechanism.