First-principles calculation on γ-Fe/La2O3 interface properties and austenite refinement mechanism by La2O3

In this paper, the interface properties and interfacial interaction were calculated by the first principle method, and the growth of gamma-Fe boundary was inhibited by La2O3 so as to refine the austenite grain was also analyzed. The calculated results show that the two-dimensional lattice mismatch between gamma-Fe(110) plane and La2O3(001) plane is 8.7%. Therefore, the nucleation interface between gamma-Fe and La2O3 is most likely gamma-Fe(110)/La2O3(001). Meanwhile, there are three kinds of interface models, which are Fe-La-OT, Fe-La-OM and Fe-La-Bridge, respectively. The interface adhesion work of Fe-La-OT interface is smallest, which is -0.10 J/m(2), while, that of Fe-La-OM interface is largest, which is -0.02 J/m(2). The ideal interface adhesion work of the three interfaces is negative, which indicates that they cannot be existed stably. The three kinds of interfacial chemical bonds are composed of ionic bonds and metallic bonds. The chemical bond polarity of Fe-La-OT interface is the strongest, and the metallic property of Fe-La-OM interface and Fe-La-Bridge interface is stronger than that of Fe-La-OT one. In addition, most interfacial interaction forces of the three interface models are repulsive, which indicates that La2O3 has a good inhibitory effect on the growth interface of gamma-Fe. Therefore, La2O3 can inhibit the growth of gamma-Fe boundaries so as to refine the austenite grains.