Nanostructure formation and carbides dissolution in rail steel deformed by high pressure torsion

The microstructure and the phase composition evolution of a commercial UIC 860V steel during high pressure torsion (HPT) were investigated by means of transmission electron microscopy, thermomagnetic analysis and X-ray diffraction. HPT leads to a decrease of the grain size to 10 nm and total cementite dissolution. In the nanocrystalline state the steel reaches the hardness of 11 GPa, which is 3 times higher than that of the initial state. The partial cementite dissolution starts already at the strain degree of gamma = 92. The carbon distribution in the iron matrix seems to depend on the deformation degree.