Analysis of the hysteresis loop in stainless steels II. Austenitic-ferritic duplex steel and the effect of nitrogen

type de publication	article dans une revue internationale avec comité de lecture
date de publication	2001
auteur(s)	Fardoun Farouk; Polák Jaroslav; Degallaix Suzanne
journal	Materials Science and Engineering A
volume (numéro)	A297
pages	154 – 161
résumé	The hysteresis loop of austenitic and austenitic–ferritic duplex stainless steels, both with different levels of nitrogen, was analyzed using a generalised statistical theory. The plot of the second derivative yields information on the average effective stress and the probability density function of the critical internal stresses, its evolution in cyclic straining and its dependence on the strain amplitude. The probability density function in duplex steels has two peaks, which correspond to the two-phase structure. The position of these peaks plotted versus the fictive stress corresponds very well to the position of the peaks in the individual phases. The changes of the effective moduli and the evolution of the effective and internal components of the cyclic stress are reported. Nitrogen takes a strong effect on the probability density function of the critical internal stresses in austenitic steel. The suppression of the second peak formed in high amplitude straining is discussed in terms of the appearance of planar dislocation structures, which develop due to the presence of nitrogen.
mots clés	Duplex steel; Hysteresis loop; Nitrogen
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