Site preference of atoms in the relaxed (111) APB of Ni3Al(X) alloys

The cluster variation method (CVM) has been widely used for solving many pr oblems of phase equilibrium in metals and alloys. In the present study, we extend the original CVM so as to perform the calculations of the energy and profile of antiphase boundaries in the intermetallic compounds such as NI- AI-X systems (X is chosen to be Fe), We calculate the site preference of te rnary elements in the relaxed (111) APE region for L1(2)-type Ni3Al(X) allo ys, based on the tetrahedron approximation of CVM I. We have found that the peak of the calculated (111) A PB energy appears at an alloy composition d eviating slightly to the Al-rich side from stoichiometry, This deviation is considered to result from the short-range effect between Ni and Al at the APE region.