Site preference of ternary alloying additions in FeAl and NiAl by first-principles calculations

First-principles calculations have been performed to investigate the site preference of ternary alloying additions in FeAl and NiAl. In FeAl, Cr and Ti are found to occupy the Al sublattice whereas Ni has a distinct preference for the Fe sublattice. The site substitutional behavior of 3d ternary elements in FeAl can be explained in terms of the trends in the heat-of-formation. In Al-rich NiAl, Fe atoms occupy exclusively the Ni sublattice. In Ni-rich NiAl, because of the small enthalpy difference between Fe occupying Al and Ni sublattices (i.e. less than 0.1 eV with a preference of Fe for Al sites at O K), the site distributions of Fe in these alloys are found to vary with alloy composition and temperature. Due to the large difference in the local magnetic moments between Fe atoms occupying Al and Ni sublattices (with values of 2.4 mu(B) and less than 0.1 mu(B), respectively) in NiAl, magnetic susceptibility measurement should be the most effective way to measure the site distributions of Fe in NiAl.