Effect of Partitioning Time on the Microstructure and Evolution of Medium Mn Q&P Steel

This study investigated the effect of partitioning time on the mechanical properties and microstructure of medium Mn steels. The steel samples were annealed at 660°C for 20 min before partitioning. The microstructure and mechanical properties of the steel were thoroughly examined. The results revealed that the specimens consisted of martensite and ferrite with varying morphologies and retained austenite (RA) distributed in different microstructure regions. After heat treatment, the RA was found to be dispersed within the microstructure. According to research, the partitioning time significantly influences grain orientation. Additionally, the stability of RA at room temperature was influenced by dislocation density. This phenomenon can be attributed to the formation of parallel stacking faults, which diminish the material capacity to obstruct dislocation movement. While this occurrence enhances plastic deformability, it adversely impacts austenite stability, especially within the face-centered cubic phase. Conversely, the resultant increase in dislocation density has been found to contribute positively to the stability of RA. Consequently, the plasticity of the medium Mn steel is significantly improved.