INFLUENCE OF FERRITE-MARTENSITE MICROSTRUCTURAL MORPHOLOGY ON TENSILEPROPERTIES OF DUAL-PHASE STEEL

The influence of ferrite-martensite microstructural morphology, volume fraction of martensite, epitaxial ferrite on the tensile behaviour of dual-phase steels, was studied. It was observed that increasing the m artensite content and its aspect ratio raised tensile strength and duc tility. Epitaxial ferrite in rolled material strongly reduced the stre ngth and improved the ductility, suggesting that substructure strength ening of material, as well as increased stress transfer to the hard ph ase, contribute to the strength of thermo-mechanically processed mater ial. Mettallographic analysis of deformed samples revealed that void n ucleation occurs predominantly along the ferrite-martensite interface. The void density in the necked region increased towards the fracture surface in all samples and was higher for samples which exhibited loca lized necking.