Tensile behavior of intercritically treated high martensite dual-phase steel

Dual-phase microstructures with varying contents of martensite were prepared by intermediate quenching (IQ) of initial martensitic microstructures of a boron-vanadium containing micro alloyed steel. Subsequently, these steels with ferrite-martensite microstructures were then investigated in order to understand their tensile behaviour. Quantitative microstructure characterization of the dual-phase steels were also carried out to correlate the microstructure with the tensile behaviour. The role of the microstructure was assessed using plots of the tensile parameters vs. corresponding volume percentage of martensite (VPM). The nature of the variation of tensile parameters for IQ treated dual-phase steels with VPM is significantly different from those reported in the literature. Best optimised properties are exhibited by dual-phase steels with equal amounts of ferrite and martensite. This unusual tensile behaviour has been explained using a model which considers the strength of ferrite and martensite as the dependent on the microstructural morphology.