Characterization of cryorolled low carbon steel using ferrite-martensite starting microstructure

Cryorolling, a severe plastic deformation (SPD) technique performed at cryogenic temperatures, has emerged as a promising technique for enhancing the microstructure and mechanical of low carbon steel. Low carbon steel with a dual-phase ferrite-martensite starting microstructure was subjected to cryorolling at liquid nitrogen temperature to produce sheets at different deformation rates: 50%, 70%, and 90%. Microstructure, mechanical properties, and corrosion resistance were investigated. The results indicate that cryorolling effectively refines the microstructure, leading to a higher dislocation density and smaller grain size as the deformation rate increases. The cryorolled sample deformed at 90% exhibits the highest grain aspect ratio (35.5), smallest crystallite size (13.70 nm), highest lattice strain (74.6 x 10-3), and highest dislocation density compared to the samples deformed at 50% and 70%. This refined microstructure significantly enhances the mechanical properties, with the cryorolled sample deformed at 90% showing the highest hardness (152 HV), tensile strength (1020 MPa), and yield strength (950 MPa), representing increases of 175.6%, 344.0%, and 466.5%. In addition, cryorolling at 90% showed a decrease in corrosion resistance, with the lowest corrosion rate observed at 90% deformation (5.97 mm/year).