Xu Taixu, He Zhijun, Han Xiao, Yang Xin, Hou Xinmei
School of Materials and Metallurgy, University of Science and Technology Liaoning, Anshan 114051, China.
Key Laboratory of Green Low-Carbon and Intelligent Metallurgy Liaoning Province, University of Science and Technology Liaoning, Anshan 114051, China.
Materials (Basel). 2023 Dec 30;17(1):223. doi: 10.3390/ma17010223.
To clarify the influence of Si on cementite nucleation during the solidification of hypereutectoid steel, the types and microstructure of cementite in hypereutectoid steel with various Si concentrations were investigated by X-ray diffraction and scanning electron microscopy. Additionally, the interfacial properties of γ-Fe/FeC were studied using the first-principles density functional theory, including work on adhesion, interfacial energy, and electronic structure, with the aim of elucidating the impact mechanism of Si on the cementite nucleation. The results showed that increasing Si concentrations (0-0.42 wt.%) had a negligible effect on the types of cementite in as-cast hypereutectoid steel. However, the average number of cementite lamellae per unit area decreased significantly, indicating that an increase in Si concentrations has an inhibitory effect on cementite nucleation. This can be attributed to the effect of Si on the interfacial properties of γ-Fe (010)/FeC (010), where the presence of Si disrupts the charge distribution of the γ-Fe (010)/FeC (010) interface and decreases the hybridization of atom orbits on each side of the interface, resulting in a decrease in the interatomic interaction force. This is reflected in the decrease in the work of adhesion (from 6.92 J·m to 6.78 J·m) and the increase in the interfacial energy (from -1.42 J·m to -1.31 J·m). As a result, the stability of the γ-Fe (010)/FeC (010) interface is reduced, making it difficult for the composite structure to form. This indicates that Si doping inhibits cementite nucleation on austenite.
为阐明硅对过共析钢凝固过程中渗碳体形核的影响，通过X射线衍射和扫描电子显微镜研究了不同硅含量的过共析钢中渗碳体的类型和微观结构。此外，利用第一性原理密度泛函理论研究了γ-Fe/FeC的界面性质，包括粘附功、界面能和电子结构，旨在阐明硅对渗碳体形核的影响机制。结果表明，增加硅含量（0-0.42 wt.%）对铸态过共析钢中渗碳体的类型影响可忽略不计。然而，单位面积内渗碳体片层的平均数量显著减少，这表明硅含量的增加对渗碳体形核具有抑制作用。这可归因于硅对γ-Fe(010)/FeC(010)界面性质的影响，硅的存在破坏了γ-Fe(010)/FeC(010)界面的电荷分布，减少了界面两侧原子轨道的杂化，导致原子间相互作用力降低。这体现在粘附功的降低（从6.92 J·m降至6.78 J·m）和界面能的增加（从-1.42 J·m升至-1.31 J·m）。结果，γ-Fe(010)/FeC(010)界面的稳定性降低，使得复合结构难以形成。这表明硅掺杂抑制了奥氏体上渗碳体的形核。
