Austempering in low-C steels: microstructure development and nanohardness characterization
- 94 Downloads
The development of multiphase steels to obtain an optimum balance between strength and ductility is a very active topic of research. In particular, carbide-free bainitic steels have shown promising mechanical properties, making them good candidates for replacing well-established first-generation steels in the automotive industry. In this work, a detailed analysis of the microstructures attainable through overaging treatments is tackled in two bainitic steels with different Si contents. The focus has been put onto the mechanical characterization, via nanoindentation, of the phases that are generated as a consequence of the change in the bainitic treatment conditions and the final cooling to room temperature. The results show the suitability of the nanoindentation technique for gaining knowledge about the underlying transformation-related phenomena and for measuring the relative difference in hardness of the various micro-constituents. The latter is a key factor in understanding the origin of the damage in this kind of steels.
This work has been carried out in the framework of the BaseForm project. This project has received funding from the European Union’s Research Fund for Coal and Steel (RFCS) research programme under grant agreement #RFCS-CT-2014-00017. The authors acknowledge Dr. F. Hisker (ThyssenKrupp) and Dr. S.M.C. van Bohemen (Tata Steel) for providing the material used in this work.
Compliance with ethical standards
Conflict of interest
The authors declare that this work is not subjected to any conflict of interest.
- 1.Godereaux S, Vivet S, Beaudoin JF (2002) Application of TRIP steels in the automotive industry. In: Proceedings of international conference on TRIP-aided high strength ferrous alloys, Mainz, Bad Harzburg, Aachen, pp 321–325Google Scholar
- 13.Ryde L, Lyytinen O, Peura P, Titova M, Vilander Granbom Y, Hebesberger T (2012) Cold-rolled complex-phase (CP) steel grades with optimised bendability, stretch-flangeability and anisotropy (CP-Steels). Publications Office of the European Union, Luxembourg, p 10Google Scholar
- 29.Molina-Aldareguia JM, Elizalde MR, Ocaña I, Gil-Sevillano J, Martínez-Esnaola JM, Iacopi F, Travaly Y, Van Hove M (2006) Use of nanoindentation to characterise the plasma damage region in low-k dielectric films. In: Proceedings of IMECE 2006 ASME international mechanical congress and exhibition, Chicago, Illinois pp 51–58Google Scholar
- 31.Timokhina IB, Liss KD, Raabe D, Rakha K, Beladi H, Xiong XY, Hodgson PD (2016) Growth of bainitic ferrite and carbon partitioning during the early stages of bainite transformation in a 2 mass% silicon steel studied by in situ neutron diffraction, TEM and APT. J Appl Cryst 49:1–16CrossRefGoogle Scholar
- 35.Liu C, Zhao Z, Bhole SD (2006) Lathlike upper bainite in a silicon steel. Mater Sci Eng A 43:4289–4293Google Scholar
- 39.Lyman T, Troiano AR (1946) Influence of carbon content upon the transformations in 3% chromium steel. Trans ASM 37:402–448Google Scholar
- 41.Caballero FG, Capdevila C, Chao J, Cornide J, García-Mateo C, Roelofs H, Hasler S, Mastrogiacomo G (2010) The microstructure of continuously cooled tough bainitic steels, In: Proceedings of 2nd international conference super-high strength steels, AIM, Milano, Italy, pp 7–20Google Scholar
- 44.Voldrich CB (1947) Cold cracking in the heat-affected zone. Suppl J Am Weld Soc 26:153s–169sGoogle Scholar
- 46.Lindberg C (1991) Proceedings of powder metallurgy conference, PM91, EPMA, Sweden, p 2Google Scholar
- 48.Krauss G (1978) Martensitic transformation, structure and properties in hardenable steels. In: Doane DV, Kirkaldy JS (eds) Hardenability concepts with applications to steel. AIME, Warrendale, pp 229–248Google Scholar
- 49.Marder AR, Krauss G (1967) The morphology of martensite in iron-carbon alloys. Trans ASM 60:651–660Google Scholar
- 51.Roberts SC (1953) Effect of carbon on the colume fractions and lattice larameters of retained austenite and martensite. Trans AIME J Met 197:203–204Google Scholar
- 53.Makinson JD, Weins WN, Xu Y, DeAngelis RJ, Ferber MK, Riester L, Lawrence RV (1998) Mechanical characterization of martensite phase using nanoindentation techniques. In: Mukherjee K, Otsuka K, Chen H (eds) Displacive phase transformations and their application in materials engineering. TMS, Warrendale, pp 391–396Google Scholar
- 56.Karjalainen LP, Taulavuori T, Sellman M, Kyröläinen A (2008) Some strengthening methods for austenitic stainless steels steel. Res Int 79:404–412Google Scholar