Room temperature low cycle fatigue behaviour of two high strength lamellar duplex ferrite–martensite (DFM) steels

Room temperarure low cycle fatigue (LCF) behaviour of two high strength Duplex ferrite-martnsite (DFM) steels with lamellar morphology developed from a commercial V-bearing low carbon microalloyed steel has been studied. Cyclic hardening and better LCF performance were observed in case of the steel containing ∼45% martensite as compared to the steel with 60% martensite exhibiting cyclic softening behaviour. Cyclic hardening/softening behaviour of the steels has been qualitatively explained in terms of dislocation phenomena involved in the cyclic plastic deformation process. Both the steels followed Coffin–Manson (C–M) and Basquin behavior. The reason for poor fatigue performance with higher amount of martensite has been attributed to the plastic strain magnification at ferrite–martensite interfaces.