Revealing the atomic-scale structure and the fracture mechanism of the α-Al2O3/γ-Fe ceramic-metal interface

Abstract

The ideal adhesion work (Wad), tensile failure process, and electronic properties for γ-Fe (111)/α-Al2O3 (0001) interface with Al- and O-terminated were systematically investigated by the first-principles calculations based on density functional theory. The results showed that the Al-terminated interface with Hcp-site and the O-terminated interface with Hcp-site were the most stable structures in all types of Fe/Al2O3 interfaces. However, the Wad of the Al- and O-terminated interface were 1.465 and 7.102 J/m2, respectively, indicating that the bonding strength of the O-terminated interface was significantly stronger than that of the Al-terminated interface. Then the tensile test exhibited the critical strain of O-terminated was 9.5% higher than that of Al-terminated interface and the ideal tensile strength was 3.5-fold that of Al-terminated. Remarkably, the failure position of the Al-terminated Fe/Al2O3 interface occurred exactly at the interface, but that of the O-terminated Fe/Al2O3 interface occurred inside the Al2O3 phase. In-depth analysis of electronic structure showed that the behavior of electrons transfer and orbital hybridization occurred near the failure position during stretching, and electron depletion between atomic layers was a signal of fracture. Further, the minimum overlap population of chemical bonds causes fractures in advance when the tensile deformation reaches critical strain. Interestingly, the failure structure of O-terminated found that Fe and O form new atomic layers, and the behavior of bonding has occurred between the two atoms.