First-principles Study On Fe/Al₂O₃ Interface

In the solid-phase interfacial reaction involving aluminum-based/iron-based metal materials,the iron-based MIL material is prepared by stacking pure iron foil and pure aluminum foil layer by layer,and a dense aluminum oxide film exists on the Al-based surface during the reaction.,thereby affecting the diffusion of the interface,the morphology of the intermetallic compound and the properties of the entire matrix.In this paper,the first principle calculation is used to study the Fe/Al₂O₃ interface.By testing the Fe and Al₂O₃ bulk and surface,the interface model is constructed according to the matching relationship of Fe/Al₂O₃interface,and the interface bonding strength,interface stability and the electronic properties and the influence of Al atom diffusion on the interface are calculated.And provide theoretical support for the engineering practice of steel/aluminum composite interface bonding.Firstly,in this paper,the basic parameters such as the lattice constant and the moduli of the iron and alumina bulks are calculated.The surface energy of the low index surface of Fe and the surface energy of Al₂O₃ at different terminals was calculated.The surface interlayer of the most stable surface was selected for testing.The results show that the Fe bulk belongs to the metal crystal and the Fe（111）surface is the most stable in the three selected low-index surfaces.The bonding mode between the O atom and the Al atom in Al₂O₃ is combined in the form of an ionic bond.The Al₂O₃（0001）surface of Al-terminated is the surface with the lowest surface energy value among the three terminal models.Analysis of the atomic position and density of states before and after relaxation of the surface atomic layer indicates that the surface effect mainly affects the outermost atom.Secondly,the interface model of Al-terminated and O-terminated is studied.The Al-terminated is divided into three types:top,bridge and center due to the different positions of the outermost Al atoms relative to the Fe（111）surface.It shows that the bridge structure in the Al-terminated is relatively stable,and the O-terminated is the most stable of the four models,and through the analysis of the density of states,it is found that the interface effect has less influence on the inner layer atoms,mainly affecting the atoms near the interface.Finally,the influence of Al atom diffusion on the interface is analyzed qualitatively.The results show that the interfacial bonding strength increases with the increase of Al atom content.It is also shown by experiments that only Al atoms diffuse through the initial oxide layer before the oxide layer is broken.After the initial oxide layer is destroyed by the volume growth of the intermetallic compound,the textured Fe₂Al₅ phase is mainly formed by rapid diffusion of Al.The oxide at the interface affects the morphology and microstructure of the iron-based MIL composite that ultimately reacts,exacerbating the formation of the tongue structure.