Giga cycle fatigue behavior of a duplex-phase high strength steel

In this study, the Giga cycle fatigue (GCF) behavior of one duplex-phase high strength steel containing bainite and martensite was investigated. It was found that the crack was initiated from inner larger bainite because the inclusion size was controlled by the Electroslag Remelting (ER) process. A white bright facet (WBF) which was generally inclined at about 45° to the applied stress axis was often observed by SEM at the fracture origin. The WBF size was in the range of short crack and stress intensity factor range at the periphery of WBF calculated by Murakami's formula, ΔKWBF, is approximately proportional to the cubic root of WBF area size – (areaWBF)1/3, viz. ΔKWBF∝(areaWBF)1/3. By data fitting, it was verified that Basquin's equation was still available in the GCF regime, and that Mayer's prediction model can better predict the S–N curve in the GCF regime.

► GCF behavior of one duplex-phase high strength steel was investigated.
► The crack was initiated from larger bainite instead of inclusions.
► The WBF size is in the range of short crack.
► The stress intensity factor range at the periphery of WBF is proportional to (areaWBF)1/3.
► Mayer's prediction model can better predict the S–N curve in the GCF regime.