On the cyclic softening behavior of SAF 2507 duplex stainless steel

AbstractThe correlation between the low-cycle fatigue behavior and microstructure of SAF 2507 duplex stainless steel has been studied. Thecyclic behavior has been analyzed through the cyclic flow stress components, i.e. the effective and the internal ones, as well as the acti-vation volume parameter. A change in the deformation mechanism occurs at De p = 1.5 · 10 3 , where the accommodation of the plasticstrain changes from the reversible to the irreversible bow-out of dislocations giving rise to a continuous increase of the internal stress. Theanalysis of the effective stress has shown that the interaction between nitrogen atoms and dislocations can be explained through a modelfor weak obstacles. Finally, above De p P 6.0 · 10 3 , dislocations on two {111} planes in the austenite can interact and form a well-developed cell structure, which increases the hardening of the phase. Consequently, the typical softening process characteristic of duplexsteels diminishes with an increase in plastic strain amplitude. 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.