Characteristics of Phase Transformation in Metallic Fine Particles (Martensitic transformation of Fe-Ni alloys, and ordering of CuAu and Cu₃Au alloys)

Abstract

Effects of particle size upon the martensitic transformation of Fe-Ni alloys and the ordering of CuAu and Cu₃Au alloys were studied. The specimens were prepared by the reduction of fine powdered solid solution of (Fe, Ni) C₂O₄. 2H₂O, (Fe, Ni)₃O₄ and (Cu, Au) CN in hydrogen at various temperatures. The Ms temperature decreases with decreasing particle size, and the particles (27.4% Ni) less than 0.7 μ do not undergo martensitic transformation even at the liquid nitrogen temperature. The rates of ordering in CuAu and Cu₃Au increase with decreasing particle size. These phenomena were discussed from the viewpoint of the behaviors of crystal imperfections in fine particles.