PNNL

Abstract

Molecular dynamics simulations are performed to study the stability of an fcc metallic interlayer phase between an iron aluminide quasicrystal approximant (QCA) phase (84.2 Al, 5.7 Fe, 5.4 Ni, and 4.7 at.% Cr) and aluminum oxides (?-Al2O3 and ?-Al2O3). The presence of the interlayer phase was experimentally observed in some regions of the inner diameter surface of a TPBAR cladding tube. The simulations employed existing many-body (MEAM and EAM) interatomic potentials to describe atomic interactions in the interlayer and QCA phases, and Buckingham+Coulomb pair interactions for the alumina and between the alumina and the QCA (or fcc). Interface systems of QCA/alumina, fcc/alumina, and QCA/fcc are modeled and the fracture energy of the interfaces is calculated. Based on the fracture energies, for the ?-Al2O3, both MEAM and EAM suggest that the fcc interlayer phase would not form. For the ?-Al2O3, the MEAM predicts that the fcc phase would form, however, the EAM predicts that it forms only if the ?-Al2O3 is Al-terminated at the interface. For the O-terminated ?-Al2O3, the EAM predicts the fcc phase would not form, consistent with the results for ?-Al2O3.