STM study of mesoband development on the low-carbon steel surface

The surface of low-carbon steel, subjected to ultrasonic finishing treatment followed by annealing, is studied. The in situ investigation of mesoband development on specimen surfaces under different strains was carried out using scanning tunneling microscopy with loading device. The presence of a surface-hardened layer allowed us to reveal the principal role of the surface layer during plastic flow of a solid. The formation of thin hardened surface layer with high density of defects hinders microscale deformation development and determines fragmentation at the mesoscale level. The latter is accompanied by formation of a folded structure textured along the conjugate direction of maximum tangential stresses.