13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- Figure 8 Cleavage initiation and propagation in hydrogen enriched duplex stainless steel, γ –austenite, α-ferrite. The results and discussion above indicate that fracture initiation and propagation in duplex stainless steel are local processes but also have coupling effects. They can behave very differently in different environments. Local approach to fracture should be applied by considering the heterogeneous mechanical behaviors in these two phases. 4. Concluding remarks Duplex stainless steels have heterogeneous mechanical and fracture behaviors in the ferrtic and austenitic phases. The cleavage behavior of the material depends strongly on the microstructure and environments. Influences of small variations of the microstructure such as phase size, ferrite content and cold deformation on the DBTT are small. Spinodal decomposition and precipitates can significantly raise the DBTT. The cleavage propagation in duplex stainless steel can be discontinuous since the austenitic phase behaves as a stopper. Acknowledgments This paper is published by permission of Sandvik Materials Technology. References [1] J. O. Nilsson: Mater. Sci. Technol. No. 8 (1992), p. 685 [2] J. Charles, Proc. Conference on DSS ’91, Les Ulis, France, Les Editions de Physique, 3 (1991) [3] J. O. Nilsson and G. Chai: Physical metallurgy of duplex stainless steels, (2010), Proc. Of Conf. DSS 2010, pp. 35. [4] G. Chai and P. Kangas, Hyper duplex stainless steels, (2010), Proc. Of Conf. DSS 2010, pp. 125. [5] M. Hättestrand, P. Larsson, G. Chai, J-O Nilsson and J. Odqvist, Materials Science and Engineering A, A 499 (2009) 489–492. [6] J.J. Moverare: in Microstresses and anisotropic mechanical behaviour of duplex stainless steels, Ph D thesis, (2001), Linköping University, Sweden. [7] R. Lin Peng, G. Chai, N. Jia, Y. D. Wang and S. Johansson: Fat. & Fract. of Engng. Mat. & (a) (b) (c)
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