Characterization of the deformed microstructure in 1Cr18NiTi stainless steel under ballistic impact

Microstructural characteristics of 1Cr18Ni9Ti stainless steel impacted by GCr15 projectiles at a velocity of 2-6 km/s was studied through the optical microscope, SEM, TEM and EBSD techniques. The experimental results show that the adiabatic shear bands beneath the crater are observed, and its width is ranging from 1 to 10 μm. The deformation twins, martensite and intersection between them are observed simultaneously under the crater, which should be attributed to the high strain rate impact. The elongated subgrains with high aspect ratio are found in the shear band, while the melt-related microstructure is observed in the shear band. The heat converted from plastic work continuously increases the local temperature and thus leads to continued softening, even melting, in the material. According to the constitutive equation, the temperature calculated inside a shear band can be rose to the melting point of the material, which explains the melt-related microstructure observed inside shear bands simply.