First-principles investigation of vanadium-modified carbidic austempered ductile iron

Abstract This study employs first-principles calculations to investigate the atomic-scale mechanisms underlying vanadium (V) modification of (Fe, Cr) 3 C carbide within carbidic austempered ductile iron (CADI). Crystal models of VC and (Fe, Cr) 3 C were constructed, and their bulk properties were systematically analyzed. The lattice misfit approach was utilized to identify matching crystal planes. Surface energy calculations were performed to determine the optimal atomic layer thickness for stable VC (110) and (Fe, Cr) 3 C (100) surface models, thereby enabling the construction of a VC (110)/(Fe, Cr) 3 C interface model. Key findings are as follows: (1) The interface demonstrates significant stability, with calculated adhesion work ( W ad ) values of 8.67 J m −2 and 8.48 J m −2 for two interfacial configurations, and corresponding interfacial energies ( γ ) of −4.51 J m −2 and −4.32 J m −2 . These results confirm that VC can form a stable bond with (Fe, Cr) 3 C. (2) The interfacial bonding is characterized by a hybrid of covalent, ionic, and metallic bonds, indicating high bonding strength. This effective bonding reinforces the (Fe, Cr) 3 C carbide structure, ultimately enhancing the performance of CADI. The research is expected to provide a deeper understanding of the atomic-level mechanisms by which vanadium (V) modifies carbides in CADI and thereby enhances its toughness.