Phase morphology and fatigue cracks nucleation in UNS S32750 Plate

M.C. MARINELLI; J.W. SIGNORELLI,; R. E. BOLMARO,; I. ALVAREZ-ARMAS

Italia

Congreso; 7th world Duplex 2007 Conference; 2007

AIM- Assoziazione Italiana de Metallurgia

The low cycle fatigue behaviour of plate UNS S32750 duplex stainless steel was characterized at Det=0.8x10-2 for specimens cut parallel and perpendicular to the rolling direction. The fatigue results indicate that specimens oriented parallel to the rolling direction reach the longest fatigue lives. Microstructural observation has revealed that the plastic deformation and further crack nucleation generally initiate in the austenite and propagate to the ferrite. Anisotropy effects were observed in relation with the material orientation although no important differences have been observed in the relative values of the Taylor factor between austenite and ferrite along (2.18/2.07) or perpendicular (2.19/2.08) to the rolling direction. The experimental findings have been analyzed in terms of the modified Hall-Petch relation for multiphase materials.  KEYWORDS Low-cycle fatigue, crack initiation, texture, microstructure