A new route to fabricate ultrafine-grained structures in carbon steels without severe plastic deformation

A new route to fabricate ultrafine-grained ferritic steel without severe plastic deformation is described. A low-carbon steel sheet with a duplex microstructure composed of ferrite and martensite was cold-rolled to 91% reduction in thickness, and then annealed at 620–655 °C. The microstructure obtained via this process was fully annealed ultrafine grains of ferrite including homogenously dispersed cementite particles. The mean ferrite grain sizes obtained were 0.49–0.85 μm.