TEM investigations of the structural evolution in a pearlitic steel deformed by high-pressure torsion

A fully pearlitic steel was deformed by high-pressure torsion up to very high strains, and the changes in the microstructure were determined by analytic and conventional transmission electron microscopy. The imposed strain leads to a fragmentation and an alignment of the cementite lamellae parallel to the shear plane. The electron energy-loss near-edge-fine structures of the Fe-L2,3-edge of the iron matrix and the cementite lamellae were measured with high spatial resolution. The results indicated that after high-pressure torsion, the iron matrix contains finely dispersed carbon-rich areas that do not show the electronic fingerprint of cementite. However, the refinement in microstructure leads to an enormous increase in mechanical strength.