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Design of a new Ni-free austenitic stainless steel with unique ultrahigh strength-high ductility synergy |
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| Affiliation: | 1. Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran;2. Materials Engineering Laboratory, Box 4200, University of Oulu, 90014 Oulu, Finland;3. Department of Materials Science and Engineering, Yonsei University, Seoul 120-749, Republic of Korea;1. Laboratoire de Matériaux, Géomatériaux et Environnement, Université de Badji Mokhtar Annaba, B.P. 12, Annaba 23000, Algeria;2. Université de Toulouse, UPS, INSA, LMDC (Laboratoire Matériaux et Durabilité des Constructions), 135, Avenue de Rangueil, F-31 077 Toulouse Cedex 04, France;3. Department of Civil Engineering, McMaster University, Hamilton, Ontario L8S 4L7, Canada;1. Indian Institute of Technology, Hauz Khas, New Delhi 110016, India;1. The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang 110819, China;2. Laboratory for Excellence in Advanced Steel Research, Institute for Materials Research and Innovation, University of Louisiana at Lafayette, Lafayette, LA 70504-4130, USA;1. Department of metallurgical engineering, JNTUCEH, Kukatpally, Hyd-72;2. Department of Mechanical engineering, NTUCEH, Kukatpally, Hyd-72;3. Department of Mechanical engineering, RIET, Kukatpally, Hyd-90 |
| Abstract: | A conceptual approach was used to design a new Ni-free austenitic stainless steel with a unique combination of ultrahigh strength and ductility. The concept was based on the alloying of the 0.05C–18Cr–12Mn (wt.%) steel by 0.39%N and heavy warm rolling (84% reduction) at 1173 K (900 °C) to achieve the yield strength of minimum 1 GPa and high tensile strength and elongation due to a proper stability of the austenite as a result of the optimized stacking fault energy (SFE). The yield strength of 1010 MPa, tensile strength of 1150 MPa and high fracture strain of 70% were measured for the steel designed. Dislocation and solid solution hardening mechanisms are introduced as the main contributors for the ultrahigh yield strength of the steel. The strain hardening is gradual and the hardening rate reaches a high level of ∼2400 MPa at a high true strain of 40% due to slow α′-martensitic transformation and mechanical twinning. Consequently, the ductility of the designed steel is excellent. |
| Keywords: | Austenitic stainless steel Ni-free steel Ultrahigh strength Ductility Martensitic transformation Mechanical twinning |
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