Microstructures and mechanical properties of dual phase steel produced by laboratory simulated strip casting

Conventional dual phase (DP) steel (0.08C–0.81Si–1.47Mn–0.03Al wt.%) was manufactured using simulated strip casting schedule in laboratory. The average grain size of prior austenite was 117 ± 44 μm. The continuous cooling transformation diagram was obtained. The microstructures having polygonal ferrite in the range of 40–90%, martensite with small amount of bainite and Widmanstätten ferrite were observed, leading to an ultimate tensile strength in the range of 461–623 MPa and a corresponding total elongation in the range of 0.31–0.10. All samples exhibited three strain hardening stages. The predominant fracture mode of the studied steel was ductile, with the presence of some isolated cleavage facets, the number of which increased with an increase in martensite fraction. Compared to those of hot rolled DP steels, yield strength and ultimate tensile strength are lower due to large ferrite grain size, coarse martensite area and Widmanstätten ferrite.