Development of Desirable Fine Ferrite Grain Size and Random Second Phase Dual-Phase Steel Microstructures Using Composition and/or Processing Modifications

Microstructural morphology is known to have a significant impact on the mechanical properties of dual-phase steels. A fine ferrite grain size and random distribution small second phase islands are desirable provide superior isotropic compared banded that typical for this type steel. rapid alloy prototyping (RAP) facility has been used investigate three different DP 800 variants by systematically varying compositions and/or process parameters ‘standard’ DP800 composition processing gives microstructure. For Variant 1, heating rate during annealing cycle after cold rolling varied between 0.65 30 °C/s 45%, 60% 75% reduction samples. It was found 15 resulted in microstructure can give best combination strength ductility because high martensite volume fraction. 2, effect changing hot rolled (HR) (ferrite–pearlite, ferrite–bainite or martensite) final investigated. Both ferrite–50% bainite fully martensite/bainite HR materials all reductions annealed microstructures with necklace finer grains ferrite–pearlite material, which gave ferrite–martensite coarser size. 3, Mn content reduced, increased Nb achieve higher pancaking stage, refined condition same hardness. After standard only 45% cold-reduced material produced than whereas samples required sizes due recrystallisation growth kinetics.