The mechanism of nanostructured steel fracture at low temperatures

Microstructural aspects of deformation and fracture of steel which is nanostructured using the technique of equal-channel angular pressing and thermal processing at low temperature (−60°C) are considered in the paper. The methods of optical and atomic-force microscopy are used to investigate deformation surfaces. The fracture character change (from a brittle cleavage to a ductile shear) at low temperatures is shown to be associated, on the one hand, with a fuzzing of grain boundaries during pressing with solid structural phases and, on the other hand, by the replacement of the prevalent plastic deformation carriers.