Tailoring the Microstructure and Mechanical Properties of Dual Phase Steel Based on the Initial Microstructure

Abstract

The effects of different initial microstructures on the microstructural features, mechanical properties, and fracture appearance of a C–Mn dual phase (DP) steel are studied. It is revealed that the martensitic and normalize initial microstructures result in excellent combination of strength and ductility due to the good distribution of the martensite particles in the DP microstructure. Conversely, the conventional ferritic–pearlitic banded structure and spheroidized one show inferior work-hardening response and mechanical properties mainly due to the fewer effect of martensite on the deformation of larger ferritic areas that are present in the resultant microstructures. On the other hand, cooling from the austenitic region to intercritical range followed by quenching results in high strength and very high incremental work-hardening exponents. This is attributed to the presence of well-defined and isolated martensite fibers in the matrix, which is shown to behave like the deformation response of composites. The fracture appearances are in general agreement with the obtained results from the tension tests.