Phase‐Field Simulation of Carbon Diffusion during Banded Structure Formation in Low‐Carbon Steel

During the cooling process after rolling, low‐carbon steel frequently develops banded structures, primarily due to the segregation of alloying elements and the uneven diffusion of carbon under a slow cooling rate during phase transformation. The current work integrates experiment and simulation to discuss the influence of various cooling rates on ferrite and pearlite bands in Cr–Mn–Ti low‐carbon steel. Meanwhile, a multicomponent multiphase‐field model is established to quantitatively analyze carbon diffusion behavior during the evolution of austenite–ferrite. The results reveal that low cooling rates and the segregation of Mn, Si, and Cr elements can promote the formation of banded structure. Furthermore, in the solute‐poor regions, slow cooling rates allow sufficient time for carbon diffusion during austenite–ferrite transformation, which leads to the extension in both carbon diffusion distance and interface migration distance, thereby generating severe ferrite bands. Additionally, in the solute‐rich regions, as the cooling rate decreases, C concentrations at A r3 temperature and A r1 temperature increase, inhibiting the nucleation and growth of ferrite, thereby resulting in strong pearlite bands. This study further elucidates the formation mechanisms of ferrite and pearlite bands, enhancing the understanding of carbon diffusion behavior during banded structure formation.