LAUSR

Abstract The ultrafine grain with the effective grain size of 1.10 μm was fabricated by intercritical deformation on low-carbon microalloyed steel, which was finer than the deformation induced ferrite transformation (DIFT) at 1.55 μm. During intercritical deformation, the DIFT process was enhanced, showing a colony distribution of the refined grains. Meanwhile, the continuous dynamic recrystallization of pro-eutectoid ferrite was developed by both the subgrains progressively trapping dislocations and the serrated boundary pinching off the elongated grains. These processes were directly observed through the grain average misorientation maps of electron back-scattered diffraction and confirmed by transmission electron microscopy micrographs.