Realization of strength-ductility balance of 10 Mn-steel by tailoring symbiosis microstructure

Medium Mn steel is considered as a third-generation advanced high-strength steel. However, the bottle-neck problems of excessive strength and insufficient plasticity seriously limited its development. In this study, a warm rolling process was employed to refine grains and acquire high-density dislocations. Subsequently, a quenching-tempering process was employed to prepare a symbiosis microstructure containing multi-phase structures and double precipitates (kappa- and V-carbides). On the premise of providing a gigapascal-level yield strength, the introduction of multi-phase structures activated various deformation mechanisms during the straining and contributed to a tensile strength of 1777 MPa and total elongation of 14.1 % in sample W500. In sample W700, the high-density dislocations in martensite gradually passed through the austenite/martensite interfaces and entered the neighboring austenite, enhancing the coordinated deformation capacity of martensite. Sample W700 exhibited a total elongation of 21.8 % and tensile strength of 1468 MPa. Combined with a microstructure analysis during the interrupted tensile deformation, the influences of martensite transformation, dislocation motion, double precipitates, and deformation twins on the work hardening and ductility are discussed in detail.