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 Murakamiʹs formula, ΔKWBF, is approximately proportional to the cubic root of WBF area size – ( a r e a WBF ) 1 / 3 , viz. Δ K WBF ∝ ( a r e a WBF ) 1 / 3 . By data fitting, it was verified that Basquinʹs equation was still available in the GCF regime, and that Mayerʹs prediction model can better predict the S–N curve in the GCF regime.