The effect of strain rate on the mechanical properties and microstructure of the high-Mn steel after dynamic deformation tests

The paper presents results of dynamic tensile investigations of high-manganese Fe-20 wt.% Mn-3 wt.% Al-3 wt.% Si-0.2 wt.% steel. The research was carried out on a flywheel machine, which enables to perform dynamic tensile tests and impact bending with a linear velocity of the enforcing element in the range of 5/40 m/s. It was found that the studied steel was characterized by very good mechanical properties. Strength of the tested materials was determined in the static tensile test and dynamic deformation test, while its hardness was measured with the Vickers hardness test method. The surface of fractures that were created in the areas where the sample was torn were analyzed. These fractures indicate the presence of transcrystalline ductile fractures. Fractographic tests were performed with the use of a scanning electron microscope. The structure was analyzed by light optical microscopy. Substructure studies revealed occurrence of mechanical twinning induced by high strain rates. A detailed analysis of the structure was performed with the use of a transmission scanning electron microscope STEM.