Re-examination of phase diagram of Fe-Pt system

The phase boundaries pertaining to gamma(2) (FePt) and gamma(3) (FePt3) phases in the Fe-Pt system have been re-exammed by measuring (1) the compositions of interphase boundaries in diffusion couples, (2) the equilibrium compositions in two-phase alloys and (3) the electrical resistivity as a function of temperature. The results obtained by the three methods are consistent with each other. The gamma (fcc solid solution) <----> gamma(2) + gamma(3) eutectoid has been found to be located at a point higher in Pt concentration and lower in temperature than in the currently adopted phase diagram, the stability range of the gamma(2) phase exhibits considerable asymmetry. Other phase boundaries, as well as the ferromagnetic <----> paramagnetic transition in the gamma(2) phase detected by the resistivity measurements, are in fair agreement with the data in the literature.