| Abstract: | Duplex ferrite/martensite microstructures with the same fibrous, network and blocky martensite content (23%) were developed by careful heat treatments. The monotonic and cyclic properties were investigated. The stress-life behaviour (S–N curves) was also determined. The results demonstrated that, of the three microstructures the fine fibrous structure produced by intermediate quenching is the best in terms of strength and ductility while the network structure developed by intercritical annealing exhibits the worst properties. However, the network structure shows the highest potentiality of cyclic hardening and the fine fibrous the lowest. The network structure has the lowest fatigue limit. The blocky structure, the monotonic behaviour of which is in between, shows the best fatigue life. The fine fibrous structure has a high cycle fatigue life equivalent to that of blocky structure but exhibits the lowest fatigue resistance in the short life range. |
