ON THE CYCLIC SOFTENING BEHAVIOR OF A DUPLEX STAINLESS STEEL

I ALVAREZ,; P EVRARD; V AUBIN; S DEGALLAIX

Berlin

Conferencia; 6th International Conference on Low Cycle Fatigue; 2008

Deutsch Verband fur Metalkunde DVM

This study deals with the correlation between the cyclic behavior and the dislocation structure development during low-cyclic fatigue of a 2507 duplex stainless steel containing 0.17% of nitrogen. Two type of fatigue tests were carried out under total strain control, in tension-compression at Äåt/2=0.5% and tension-compression-torsion at Äåteq/2=0.5%. Interrupted tests at different numbers of cycles have been performed for characterizing the dislocation structure associated with the cyclic behavior. The results have shown that at the applied total strain amplitude the austenitic phase develops a planar arrangement of dislocations during all the fatigue life. On the contrary, the ferritic phase evolves from a homogeneous distribution of dislocations during the first cycles to a structure of dislocation bundles in the tension-compression test and a refined wall structure in the tension-compression-torsion test. It is propose in this work that the evolution of the dislocation structure in the ferritic phase plays and important role during the softening stage in the present DSS.