Dependence of tensile properties on microstructural features of bimodal-sized ferrite/cementite steels

A medium-carbon steel was processed through different warm rolling techniques, and the microstructural features with bimodal grain size distribution were found to be different. The combination of strength and ductility was ameliorated in the steel processed through warm rolling characterized by biaxial reduction. The enhanced strength is attributed to the densely distributed fine intragranular cementite particles and the small grain size in the coarse grain regions. The enhanced uniform elongation is due to the improved work hardening behavior at the large-strain stage. This work hardening behavior is predominantly ascribed to the finely dispersed intragranular particles. The relatively small grain size with nearly equiaxed shape in the coarse grain regions helps stabilize the uniform deformation to a large strain.