Low cycle fatigue behaviour of a multiphase medium carbon microalloyed steel processed through rolling S. Sankaran a , V. Subramanya Sarma b, * , Gouthama a , S. Sangal a , K.A. Padmanabhan c a Indian Institute of Technology, Kanpur 208016, India b Leibniz Institute for Solid State and Materials Research, (IFW) Dresden, Helmholtz Strasse 20, Dresden 01069, Germany c South Asia International Institute, Liberty Crossroads, Hyderabad 500029, India Received 19 May 2003; received in revised form 12 June 2003; accepted 12 June 2003 Abstract A multiphase (ferrite–bainite–martensite) microstructure was developed in an automotive grade medium carbon microalloyed steel 38MnSiVS5 through a two-step cooling and annealing process following controlled rolling. The tensile and low cycle fatigue properties of the multiphase steel are reported and compared with those of multiphase and tempered martensite microstructures obtained by forging. Ó 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Microalloyed steel; Rolling; Ferrite–bainite–martensite; Low cycle fatigue 1. Introduction In view of their capacity to develop high strength by limited alloying and ease of processing, medium carbon microalloyed (MA) steels are very cost-effective compared with quenched and tem- pered (Q&T) steels for the production of auto- motive components. To be able to substitute Q&T steels in critical applications, MA steels must be processed to similar strength levels with acceptable toughness (ductility) [1]. The development of a multiphase (ferrite–bainite–martensite: F–B–M) microstructure through controlled thermome- chanical processing is expected to result in high strengths with reasonable ductility, which is con- trolled by the volume fraction of ferrite [2,3]. Using a two step cooling procedure following a low temperature finish forging, F–B–M micro- structures were obtained with very high tensile strength and reasonable ductility in an automotive grade MA steel 38MnSiVS5. It was shown that the F–B–M microstructure displayed a significantly stronger cyclic stress–strain (CSS) response and endurance limit but similar low cycle fatigue life compared with the Q&T microstructure [4–6]. As rolling is the most widely used industrial manu- facturing process, it is interesting to see if the * Corresponding author. Tel.: +49-351-4659203; fax: +49- 351-4659320. E-mail address: v.sarma@ifw-dresden.de (V. Subramanya Sarma). 1359-6462/03/$ - see front matter Ó 2003 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/S1359-6462(03)00363-4 Scripta Materialia 49 (2003) 503–508 www.actamat-journals.com