International Journal of Fatigue 25 (2003) 481–488 www.elsevier.com/locate/ijfatigue Anisotropy effects on the fatigue behaviour of rolled duplex stainless steels A. Mateo a,* , L. Llanes a , N. Akdut b , J. Stolarz c , M. Anglada a a Dept. Ciencia de los Materiales e Ingenierı ´a Metalu ´rgica, Avda. Diagonal 647, Universitat Polite `cnica de Catalunya, 08028 Barcelona, Spain b OCAS N.V., The Research Center of the SIDMAR Group, John Kennedylaan 3, B-9060 Zelzate, Belgium c Ecole Nationale Superieure des Mines, URA CNRS 1884, 158 cours Fauriel, 42023 Saint-Etienne Cedex 2, France Received 3 May 2002; received in revised form 11 November 2002; accepted 2 December 2002 Abstract Duplex stainless steels (DSSs) produced by rolling have a significant anisotropy in mechanical properties. The present research deals with this anisotropy, paying particular attention to fatigue behaviour in the high-cycle fatigue regime. In doing so, the mechan- ical response of a 5 mm thick rolled plate of EN 1.4462 type duplex steel was characterised. Marked anisotropy effects are observed, with the transverse orientation exhibiting a mechanical response higher than that of the longitudinal one. These experimental findings are rationalised considering the correlation between the crystallographic texture of each phase and their behaviour with respect to crack nucleation and early growth of short cracks.  2003 Elsevier Science Ltd. All rights reserved. Keywords: Anisotropy; Duplex stainless steels; High cycle fatigue; Crystallographic texture 1. Introduction During the last decades, much effort has been devoted to producing duplex stainless steels (DSSs) with an advantageous cost/performance ratio. As a result, this type of corrosion resistant alloy has become established as a standard material for applications in a wide range of industrial sectors, mainly chemical and petrochemical, off-shore, paper production and pollution control equip- ment [1,2]. In most cases, DSSs are selected because they combine high strength with excellent corrosion resistance. DSS goods may be obtained through several pro- cessing routes: casting, rolling, forging and extrusion, among others. For a given chemical composition, the process type as well as the specific processing para- meters may distinctively affect the intrinsic microstruc- tural and mechanical characteristics of the manufactured products. Hot or cold deformation to produce wrought DSSs, either plates or rods, leads to alignment of crystal- * Corresponding author. Fax: +34-934016706. E-mail address: antonio.manuel.mateo@upc.es (A. Mateo). 0142-1123/03/$ - see front matter  2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0142-1123(02)00173-1 lographic axes of grains into preferred orientations, i.e. pronounced crystallographic texture. It also induces microstructural fibering: elongated grains or bands. Since the microstructure of wrought DSSs is anisotropic, the mechanical properties can be expected to be aniso- tropic as well, similar to composite materials. Clear and unusually large strength directionality effects on a 2205 (EN 1.4462) DSS, both cold- and hot- rolled, have been documented by Hutchinson et al. [3,4]. Similar results are also presented by Ul Haq et al. [5]. These effects are more significant for the cold-rolled case than for the hot-rolled one and anisotropy tends to rise with decreasing plate thickness (i.e. increasing rol- ling reduction). Furthermore, in the thinner plates the texture of individual phases is not only remarkably sharper than that of single phase stainless steels but also differs in character [4]. However, and quite distinct from findings on other commonly used structural materials, DSS flat products have a significantly higher strength in the transverse direction than in the rolling one. Hence, it has been concluded that marked anisotropy of strength may occur in DSSs because of the presence and interplay of sharp preferred crystallographic orientation in the two separate phases [3–5].