A nanograined/ultrafine-grained low-carbon microalloyed steel processed by warm rolling

We have obtained grain refinement in the nanoscale regime (~300–400 nm) by combining dynamic transformation, intragranular nucleation ferrite, and dynamic recrystallization. We elucidate a novel thermomechanical process and microalloy design to obtain ferrite–martensite microstructure with nanoscale features in low-carbon chromium-containing steel with yield strength, tensile strength, and elongation of 745 MPa, 935 MPa, and 19.5%, respectively. The mechanism associated with increased work hardening and superior formability is discussed.