Atomic-scale characterization of the site occupancies in the B2 FeAl phase: Effects of Ni addition, temperature and lattice misfit

A microscopic phase-field model is constructed to study the influences of Ni addition, temperature and lattice misfit on the site occupancies in complex B2 FeAl–Ni intermetallic phase. The tendencies of six site occupancies are explored through tracing the atomic site occupation probability. The results reveal that six site occupancies are monotone functions of Ni concentration, temperature and the lattice misfit, respectively. For the antisite behavior of Fe (Al_Fe), Al (Fe_Al) and the substitution behavior of Ni (Al_Ni, Fe_Ni), the ranks of four defect occupancies are identical under three factors. The transformation rate and ordering degree of the complex FeAl–Ni are dependent of three factors. The mechanism of configuration of six site occupancies is revealed from the energy analysis. The results are in accordance with experimental and theoretical data and provide theoretical support to the questioned validity of the lattice misfit effect on the ordering behavior in intermetallics.