Production of ultrafine equiaxed ferrite in a low carbon microalloyed steel by thermomechanical treatment

Ultrafine ferrite, with an average grain size of approximately 1 μm, has been produced using laboratory hot torsion tests. The tests utilized controlled hot deformation and cooling, with the final deformations being close to the austenite to ferrite transformation temperature when maximum refinement was observed. It is proposed that the refinement is due to strain induced transformation of a heavily controlled rolled initial austenite microstructure.