Abstract
The characteristics of Fe-Ni alloy, its A3-transformation and phase boundary between γ and α in the state of equilibrium, have been studied. It is naturally expected that, on cooling or heating with a marked hystersis, the lattice alone can be transformed without any change of concentration. And such lattice transformation was found by these researches to occur only at the time when they were superheated or supercooled beyond the co-existing range of two phases. From the temperature of lattice transformation, the equilibrium diagram of that alloy were drawn in a solid state.
