PHASE MORPHOLOGY AND FATIGUE CRACKS NUCLEATION IN

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

Italia

Conferencia; Duplex 2007; 2007

Associazione italiana di 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