Annealing behavior of nano-layered steel produced by heavy cold-rolling of lath martensite

A study of the annealing behavior of nano-layered steel produced by heavy cold-rolling of lath martensite has been conducted. The results show that the nano-layered structure of lath martensite was stable until annealing at 623 K for 3.6 ks. Subsequently, discontinuous recrystallization began in some regions after 673 K annealing and finished after 873 K annealing. The nano-layered structure in the specimens annealed for 3.6 ks at 673-773 K changed into the multiphase nano-structure composed of equiaxed ferrite grains and carbides. Furthermore, the phenomenon of fracture delamination was observed from the tension fractures of the specimens as-rolled and annealed up to 773 K for 3.6 ks. In addition, the mechanisms of structure stability and mechanical behavior are also discussed.