Correlating the lattice parameter and Curie temperature of γ-Ni in Fe-Ni-base alloys

We report a correlation between the Curie temperature (TC) and lattice parameter (a) of γ-Ni phase in Fe-Ni-base alloys. The Bethe-Slater curve represents the dependence of exchange integral (J) on the ratio of the interatomic spacing (D) to the diameter of 3d orbital (d) of an element. According to the mean field model, the exchange integral J is directly proportional to the TC. A large number of Fe-Ni base alloys were surveyed to establish a mathematical relationship between TC and D/d, as well as to predict the TC of FCC γ-Ni phase by estimating its lattice parameter.