Revealing the interface energy and electronic properties of NbN/α-Fe in shipbuilding steels

Abstract

In this work, the low index interfacial configuration, interface energy and electronic properties of the NbN/α-Fe interface in shipbuilding steels were investigated by using the first-principles method and ab initio molecular dynamics simulation calculations. Additionally, the NbN/α-Fe interface with the low index interfacial configuration was calculated by two-dimensional disregistry method. It is shown that the relaxation optimization of the NbN(001)/α-Fe(001) structure is carried out and the interfacial energy of Fe-Nb type, Fe-bridge type and Fe-C type NbC(001)/α-Fe(001) structure is calculated, the Fe-N type has an interfacial energy of −1.659 J/m2, the smallest interfacial energy and thus is the most stable. Thereby, the Fe-N type is the most stable conformation of NbN(001) /α-Fe(001). There are strong orbital resonance phenomena between Fe-3d, Nb-4d and N-2p, producing strong metallic and covalent bonds. The results of disregistry calculation by different interfacial structures of NbN/α-Fe showed that the disregistry of NbN(001)/α-Fe(001) crystalline surface was the smallest at 8.65 %, which matches well with the results of interfacial energy calculation. The results indicated that the α-Fe(001) is the optimal orientation surface of the NbN(001). This study reveals the stable bonding mode and site-oriented relationship of NbN/α-Fe interface in steel, which provides important theoretical guidance to explore the mechanism of grain refinement of NbN particles in shipbuilding steels.