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

• 来源期刊: 纳米材料科学（英文版）
• 年，卷（期）: 2020,（1）
• 页码范围: 83-95
• 页数: 13页
• 语种: 中文

摘要

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,gains 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 sizes ＜ 1 μm) mainly composed of GNBs having high misorientation angles.Decreasing Z with increasing temperature and/or decreasing strain rate accelerated thermally activated processes,such as dynamic recovery and boundary migration.Unlike the ultrafine lamella formed under the high-Z condition,a variety of microstructures having equiaxed morphologies with fine to coarse grain sizes (＞1 μm) 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.