Monotonic tensile and fatigue crack growth tests have been performed on AISI 1018 and Fe/2Si/l).lC steels with duplex ferrite-martensite (DFM) microstructures. The effects of microstructure on ambient temperature mechanical properties were examined. Two distinct martensite distributions were produced in AISI 1018 DFM. The primary differences between the two were the ferrite and martensite particle sizes. It was found that tensile fracture was sensitive to both martensite distribution and volume fraction. For a given volume fraction of martensite, large particle sizes increased strength but drastically reduced ductility.Threshold stress intensity ranges for fatigue crack growth in AISI 1018 DFM were found to be unaffected by the distribution or the volume fraction of martensite • -5 -3 / However, crack growth rates in the range of 10 to 10 mm cycle were increased in AISI 1018 DFM when the particle sizes were large. The increased crack growth rates were attributed to a crack extension mechanism involving cleavage fracture in ferrite. The Fe/2Si/0.1C DFM alloy was found to have a considerably higher fatigue threshold stress intensity than AISI 1018 DFM of comparable strength. The -2 -greater near-threshold fatigue crack propagation resistance in Fe/2Si/O.le DFM was attributed to a meandering crack path, generated by the coarser microstructure in this steel, which promotes roughness-induced crack closure and crack deflection effects.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.