High-Resolution EBSD Study of Adiabatic Shear Band and Neighboring Grains After Dynamic Impact Loading of Mn-Steel Used in Vehicle Structure

We report the results of the microstructural characterizations and micro-texture analysis of a lightweight austenitic steel deformed at high strain rate (1200 s⁻¹) using a split Hopkinson pressure bar. Formation of adiabatic shear bands (ASB) and plastic deformation mechanisms within neighboring grains are investigated by high-resolution electron backscatter diffraction (HR-EBSD). HR-EBSD reveals formation of athermal ε-martensite and ά-martensite within the shear bands, resulting in the formation of a brittle intersection structure. Crack initiation and propagation is seen in intersection structure. The thermally induced ε-martensite follows Shoji-Nishiyama crystallographic orientation relationship with parent austenite phase, while ά-martensite shows Burgers relationship with ε-martensite. A detailed examination depicts the presence of deformation twins in grains adjacent to the ASB. Furthermore, strain-induced ε and ά martensite are formed in the neighboring grains of ASB. The micro-texture of martensite variants is discussed in ASB and in the neighboring grains.