Construction and regulation of heterogeneous structure in medium Mn steel with critical annealing − quenching and partitioning process

The heterogeneous structure formed by the specific process is very effective in balancing the strength and plasticity of the metal material. The heterogeneous structure formation, evolution and strengthening mechanism have not been clearly understood, especially its potential in the microstructure design of medium manganese steel (MMS) has not been explored. In this work, the composition and characteristic genetic behavior of heterogeneous structure were studied during the casting billet, hot rolling, warm rolling and critical annealing − quenching and partitioning (IA-Q&P) process. It is found that the specific hot rolling and warm rolling processes are conducive to the formation of heterogeneous structure in MMS, and the warm rolling and IA-Q&P processes could refine grain and increase the dislocation density, thus improving the mechanical properties. In addition, the IA-Q&P process could also consume the recrystallization structure and reduce the Schmidt factor in the grain, so as to further improve the mechanical properties and deformation resistance. In summary, the study of the formation of heterogeneous structures in MMS is of great significance for improving the strength and plasticity of MMS.