The Phase Transformation of Iron Rich Iron-Nickel Alloy in Fine Particles

Abstract

Studies on the equilibrium diagram and characteristics of phase transformation of Fe-Ni alloy in fine particles were carried out by X-ray diffraction and specific heat measurement. The specimens were prepared by reduction of solid solution Fe _x Ni_1-x C₂O₄ in hydrogen at various temperatures below 800°C. The fine particles reduced at temperatures below 600°C did not undergo a martensitic transformation even when they were cooled to room temperature. The diagram determined by the reduction method is in close agreement with those obtained by annealing of bulk alloys for very long periods. Therefore the diagram was easily determined because of the absence of martensitic transformation and furthermore because of the acceleration effects during reduction upon the diffusion rate. The existence of the superstructure Fe₃Ni was suggested by the specific heat measurement.