Compositional effect on local structure of (Fe-Ni)75B25

The structure model of metallic glasses has been discussed. The experimental results of the NMR and Moessbauer studies suggested that the local atomic environment is somewhat better ordered than that predicted by the dense random packing (DRP) model. This paper reports on the first direct structural evidence of such systematic deviation from the random packing behavior. Energy dispersive X-ray diffraction (EDXD) studies were performed on Ni(50)Fe(25)B(25) and Fe(75)B(25) alloys. The reduced interference function and the radial distribution function (RDF) for these compositions were obtained. It is possible to directly compare the structures of these amorphous and crystalline solids. The crystalline structure of Ni3B is orthorhombic, while that of Fe3B is probably tetragonal. The characteristics of RDF of Ni3B and Fe3B were compared with those of Ni(50)Fe(25)B(25) and Fe(75)B(25). The results showed that a compositional effect on the structure other than the size effect existed in this alloy system, even though Fe and Ni are physically and chemically similar. The first direct evidence that the local environment in these alloys deviates from that in the DRP model toward the environment in the corresponding crystalline compounds was seen. (Kato, T.)