Strain-dependence of deformation microstructures in ultra-low-C IF steel deformed to high strains by torsion at elevated temperatures

摘要

cqvip:Single-phase bcc-ferrite in an interstitial free(IF)steel was deformed to different strains in a wide range from low to high strains(ε=1–7)by torsion under different Zener-Hollomon(Z)conditions.The specimens were rapidly quenched after the torsion to preserve microstructures formed under different deformation conditions.The results showed that during high-Z(low-temperature)deformation,grains were subdivided by geometrically necessary boundaries(GNBs)via the grain subdivision mechanism.Deformation to high strains(ε>5)led to the ultrafine lamellar structures(with grain sizes1μm)were realized with decreasing Z.The significance of the grain subdivision and the thermally activated phenomena on the formation of various microstructures under different deformation conditions is discussed.