Short Crack Growth Behavior in Ferrite-Bainite Dual Phase Steels

The effect of bainite content on the short crack growth behavior of three ferrite bainite dual phase steels has been examined using a rotating bending machine together with examinations of the microstructural constituents associated with the fatigue crack path. The magnitude of ΔKthsc for ferrite bainite dual phase steels, in general, is found to increase with increasing amount of bainite. Critical examinations of the crack paths indicate that it is inter-granular for steels with < 70% bainite while it is intra-granular for steels containing > 70% bainite.