Architectured heterogeneous microstructure of medium-Mn steel through cold rolling and intercritical annealing to improve deformation behavior

A bimodal heterogeneous structure was successfully obtained in Fe-11.9Mn-1.68Al-1.49Si-0.26C steel through cold rolling and intercritical annealing. It achieved an excellent combination of strength and ductility, and the product of strength and elongation (PSE) reached 57.3 GPa center dot%. The (hetero-deformation induced) HDI stress was induced into the medium-Mn steel during deformation due to heterogeneous structure. Yet, the microhardness difference between soft and hard components decreases with the increase of annealing temperature, resulting in the decrease of the HDI stress. The deliberately introduced micron-sized austenite grains facilitate to activate the intragranular dislocation sources, alleviates stress/strain concentration to a certain extent, which contributes to avoiding discontinuous yielding and L & uuml;ders strain. Metastable austenite exhibits multiple microplastic mechanisms during deformation, such as stacking faults, epsilon-martensite, and deformation twins, which cooperate with HDI strengthening to improve the strength and plasticity.