Formation and Mechanical Properties of Bimodal Microstructures in 0.2 Carbon Steel by Heavy-Reduction Hot Compression

摘要

A compression test simulating heavy-reduction single-pass rolling was conducted to investigate the compression behavior and to systematically collect basic data on the formation of bimodal structures in 0.2% carbon steel at various deformation temperatures from 700 to 850°C. As increasing deformation temperature from 700 to 850°C, those microstructures were considerably refined with higher fraction of high-angle grain boundaries. Particularly, there was high a probability of bimodal structures being formed in 850°C-compressed sample having 1.4 μm of average ferrite grain sizes. Ultimate tensile strength and average uniform elongation (UE) of this sample represented 677 MPa and 8%, respectively, which shows holding high strength and twofold improved UE compared with the other samples. Additionally, bimodal dimples with submicron-size (<1 μm) and fine (2-4μm) dimples were observed on the fracture surface in the sample compressed at 850°C.