First-Principles Investigation of the Stability, Electronic Structure, and Mechanical Properties of M (Mn, Ti, Mo)-Doped α -Fe

Ferrite (α-Fe), as the fundamental phase of steel materials, plays a decisive role in determining their macroscopic mechanical behavior through its microscopic properties—particularly in engineering applications involving resistance to plastic deformation and fracture, fatigue resistance, wear resistance, and low-temperature toughness. Therefore, alloying elements are commonly introduced to improve the performance of steel via mechanisms such as grain refinement strengthening and precipitation strengthening. However, these strengthening mechanisms have not thoroughly investigated the effects of doped alloying elements on the stability, electronic structure, and mechanical properties of ferrite itself. In this study, orthogonal experimental design and first-principles calculations were employed to investigate the effects of ternary alloy doping with M (Mn, Ti, Mo) on the stability, electronic structure, and mechanical properties of a ferrite-based supercell model Fe16-x-y-zMnxTiyMoz (x, y, or z = 0, 1, or 2). The aim is to provide both theoretical insight and experimental reference for improving the comprehensive performance of ferrite-based steels by modifying the properties of the matrix phase. The results of the formation enthalpy (Hform) calculations indicate that all solid solutions have negative formation enthalpies, suggesting that they can form spontaneously. Among them, Ti doping is the most favorable for solid solution formation, followed by Mn, while Mo is the least favorable. The Fe₁₃Ti₁Mo₂ configuration is the easiest to form spontaneously. The cohesive energy (Ecoh) results demonstrate that all solid solutions exhibit structural stability.Fe₁₃Ti₁Mo₂ has the largest (most negative) cohesive energy of -477.96 eV, indicating it possesses the highest structural stability. Mo doping contributes the most to stability enhancement, followed by Ti, while Mn has the least effect. Electronic structure calculations reveal that M doping consistently reduces the density of states (DOS) at the Fermi level for Fe16-x-y-zMnxTiyMoz. The lowest DOS at the Fermi level, 4.294, is found inFe₁₃Ti₁Mo₂, indicating enhanced hybridization and overlap between Mn 3d, Ti 3d, Mo 4d, and Fe 3d states. This strong hybridization leads to a lowering of the Fermi level and contributes to the high stability of theFe₁₃Ti₁Mo₂ phase. Mechanical property calculations suggest that M doping reduces the Young’s modulus (E) and Vickers hardness (Hv) of the solid solutions. However, the K values (K=GH/BH) are all greater than 1.75, and Poisson’s ratios (ν) exceed 0.26, implying that while stiffness and hardness decrease, the ductility of the materials is improved. This provides valuable guidance for the design of ductile and tough ferrite-based steel materials.