First principles investigation on interface properties and formation mechanism of γ-Fe/CeO2 heterogeneous nucleation interface

The first principles method was used to calculate the interface stability, interfacial electronic structure and bond characteristics of γ-Fe/CeO2 heterogeneous nucleation interface. Meanwhile, The formation mechanism of (100)_γ-Fe/(111)_CeO2 heterogeneous nucleation interface was also revealed. The calculation results show that the two dimensional lattice mismatch between (100)_γ-Fe and (111)_CeO2 is 4.9%, which indicates that (100)_γ-Fe and (111)_CeO2 satisfy the crystallographic condition for the formation of effective heterogeneous nucleation interface. There are two kinds of interface models, named as O1-Fe and O2-Fe. The stability of O1-Fe interface is the best and its interfacial energy is the lowest, which is 3.07 J/m2. The ideal interfacial adhesive strength of O2-Fe interface is the largest, which is 10.98 J/m2. The bond characteristics of the two interfaces are both mixtures of covalent bonds and ionic bonds. It reveals that (100)_γ-Fe and (111)_CeO2 can form effective heterogeneous nucleation interfaces and O1-Fe interface model forms preferably during the heterogeneous nucleation beginning process. When the formation conditions meet the requirement for both interface structures, the adhesive strength of the O2-Fe interface is higher. Therefore, CeO2 can act as effective heterogeneous nucleation substrate of γ-Fe to refine the austenite grains.