Objective functions on minimizing the atomic volume elastic strain and the atomic
size misfit in close--packed directions
due to the atomic substitution in sublattices of γ' phase are
established, respectively. Constrain conditions on equilibrium partition of a1loying elements and on
their concentration range in sublattices of γ' phase are correspondingly built up. Using superalloys
CMSX--2 and SRR99 as objects investigated and adopting a compound optimization calculation method
with the Powell and the Simplex algorithms, the elemental concentration and the site fraction of the
two sublattices can be calculated. In addition, a calculation formula on
lattice parameter of γ' phase
closely associated with the elemeotal concentration and with the site occupancy of the sublattices is
derived. All the calculated results by use of the present methods show quite good accordance with the
reported values. The method proposed can predict the elemental concentration in sublattices and the
lattice parameter of γ' phase when the chemical composition of the γ' phase investigated is known.