Superior combination of strength and ductility in Fe-20Mn-0.6C steel processed by asymmetrical rolling

A Ce-alloyed twining-induced plasticity steel with the gradient structure was prepared through asymmetrical rolling. The primary role of Ce addition was to refine grains, and the asymmetrical rolling also effectively reduced grain sizes, and increased dislocation density. Under the combined effects of asymmetrical rolling and Ce addition, the steel exhibited superior combination of strength and ductility, with the yield strength of 1320 +/- 5 MPa, ultimate tensile strength of 1775 +/- 10 MPa and good elongation of 27 +/- 1 %. Dislocation strengthening was the key factor of the increasing yield strength. As grain size decreased, the thicknesses of twins were significantly refined to several nanometers, accompanied with the activation of secondary twins. The promoted TWIP effect effectively enhanced the strain hardening ability of the steel.