An experimental investigation of tensile properties and fatigue crack growth behaviour for Dual-Phase Steel / Roslinda Idris...[et al.]

This paper presents the fatigue crack growth behaviour of a dual-phase steel. The fatigue strength of dual-phase steels can be influenced by their inherent microstructural phases, where hard martensitic phases are dispersed in a soft ferritic matrix. The main objective of this study is to investigate the fatigue crack growth behaviour of a dual-phase steel. The dual-phase steel was achieved by inter-critical heat treatments which specifically aimed to increase the resistance of the steel to fatigue loading. The tensile properties of dual-phase steels have been studied through tensile testing methods, while their fatigue crack growth behaviours have been experimentally investigated using compact-tension specimen under constant amplitude loading. The experimental results indicated that the fatigue crack growths in as-received steels could propagate more freely than that in dual-phase steel microstructures; thereby giving dual-phase steels a longer fatigue life compared to the as-received steels. A crack growth of about 22 % lower was observed in the dual-phase specimens compared to the as-received specimens. Finally, the variation of fatigue crack growth rate with stress intensity factor range for as-received and dual-phase steels was discussed within the Paris region. It was concluded that the presence of second hard phases (martensite) in dual-phase steel effectively retarded crack growths.