Superior strength of carbon steel with an ultrafine-grained microstructure and its enhanced thermal stability
- 374 Downloads
The paper presents the results of a study on the microstructure and mechanical properties of a medium-carbon steel (0.45 % C) processed by severe plastic deformation (SPD) via high-pressure torsion (HPT). Martensite quenching was first applied to the material, and then HPT processing was conducted at a temperature of 350 °C. As a result, a nanocomposite type microstructure is formed: an ultrafine-grained (UFG) ferrite matrix with fine cementite particles located predominantly at the boundaries of ferrite grains. The processed steel is characterized by a high-strength state, with an ultimate tensile strength over 2500 MPa. Special attention is given to analysis of the thermal stability of the microstructure and properties of the steel after HPT processing in comparison with quenching. It is shown that the thermal stability of the UFG structure produced by HPT is visibly higher than that of quenching-induced martensite. The origin of the enhanced strength and thermal stability of the UFG steel is discussed.
KeywordsMartensite Cementite Severe Plastic Deformation Martensite Plate Supersaturated Solid Solution
M.V. Karavaeva gratefully acknowledges the financial support from the RFBR, project No.14-08-90429. M. M. Ganiev and L. A. Simonova gratefully acknowledge the funding through the Russian Government Program of Competitive Growth of Kazan Federal University. R.Z. Valiev gratefully acknowledges the Russian Federal Ministry for Education and Science (through RZV Grant No. 14.B25.31.0017). A.V.Ganeev is greatly acknowledges of A.von Humboldt foundation (Group Linkage Project Fokoop —DEU/1052606).
- 2.Okitsu Y, Takata N, Tsuji N (2009) A new route of fabricate ultrafine-grained structures in carbon steels without severe plastic deformation. Scripta Materialia 60:76–79Google Scholar
- 5.Valiev RZ, Alexandrov IV (2007) Bulk nanostructured metallic materials. Akademkniga, Moscow (in Russian)Google Scholar
- 12.Ganeev AV, Karavaeva MV, Sauvage X et al (2014) On the nature of high-strength state of carbon steel produced by severe plastic deformation. IOP Conf. Series. Mate Sci Eng 63:012128Google Scholar
- 17.Wang J, Xu C, Wang Y et al (2003) Microstructure and properties of a low carbon steel after equal channel angular pressing. In: Zehetbauer MJ, Valiev RZ (eds) Nanomaterials by severe plastic deformation. J WileyVCH, Weinheim, pp 829–834Google Scholar
- 20.Valiev RZ, Enikeev NA, Langdon TG (2011) Towards superstrength of nanostructured metals and alloys, produced by SPD. Kovove Mater 49:1–9Google Scholar
- 26.Nishiyama Z (1978) Martensitic transformations. Academic Press, New YorkGoogle Scholar
- 27.Askeland D., Wrigth W. (2013) Essentials of materials science & engineering. SI Edition, Cengage Learning Stamford, USAGoogle Scholar
- 28.Goldstein MI, Litvinov VS, Bronfin BM (1986) Metal physics of the high-strength state. Metallurgiya, Moscow (in Russian) Google Scholar
- 36.Takaki S (2010) Effect of carbon and nitrogen on the Hall–Petch coefficient of ferritic iron. Mater Sci Forum 638–642:173–186Google Scholar