Structure and interfacial properties of η-Al5Fe2/Fe heterogeneous interface: First principles calculation and experimental research

Metal/intermetallic compound heterointerfaces are ubiquitous in bimetallic materials, and their microstructures frequently determine the properties of the material. Combining transmission electron microscopy with density functional theory calculations, we investigated the interaction and bonding characteristics at Al5Fe2/Fe interfaces. It is found that the interface orientation relationships between Al5Fe2 and Fe can be expressed as: Al5Fe2 (1_1_2) // Fe (01_3); Al5Fe2 [110] // Fe [231]. In iron-rich conditions, the AlFe2- terminated Al5Fe2(1_1_2) surface is the most stable one among the four terminations. The calculated works of adhesion and electronic structures indicate that the Fe-AlFe1-MT/HCP configuration of Al5Fe2(1_1_2)/Fe(01_3) exhibits the strongest interfacial bonding properties, with strong metal-metal interactions between the atoms. The charge density is quite large inside the atoms of the interface owing to the considerable charge transfer between them. It is localized, indicating the strong covalent interaction between atoms. Thus, the interfacial interaction can be strong, and direct metal-metal interactions can play a critical role in metal/ intermetallic compound heterointerfaces with large mismatches, opening up a new avenue for understanding the origins of interface-related issues.