Preparation of diversified ultra-fine microstructures in Q345 steel with improved properties

A typical C-Mn steel (Q345) with warm-rolled ferrite/pearlite was used for subsequent simple process resulting in ultrafine ferrite grains in size of ∼1μm. No remarkable strain hardening was detected and grain boundary motion was also recognized as an important accompanying deformation mechanisms at the beginning of yielding. However, strain-hardening capability of this C-Mn steel could be improved by changing the ultrafine ferrite/pearlite into acicular ferrite with increment of strength.