Published online by Cambridge University Press: 21 March 2011
The structure of ternary and quaternary NiAl-based ordered intermetallic alloys is studied using the BFS method for alloys. A simple calculational procedure, based on the determination of the energetics of local environments surrounding defect atoms is introduced and applied to the study of the defect structure and phase formation in NiAl-based systems. The procedure is illustrated with two different examples: 1) the phase structure of Ni-Al-Fe alloys, focusing on the concentration dependence of the site preference behavior of Fe in NiAl, and 2) the precipitation of a β′ phase in NiAl(Ti,Hf) alloys, focusing on the role of Hf in lowering the solubility limit of Ti in NiAl, thus enhancing the precipitation of a Heusler Ni2Al(Ti,Hf) phase.