The structure of quenched Ni3(Mo, Ta) alloys containing 2 and 5 at % Ta was investigated by transmission electron microscopy. It was found that the DO22-type ordered phase was formed in the Ni3(Mo, Ta) alloy containing 5 at % Ta quenched from 1300°C. The changes in structure, interaction energy and strain energy with increasing Ta content are discussed. It is described by using a tetrahedron model that regions which take Ni3Mo-type tetrahedron in FCC lattice site will either extend or increase in number, or both with increasing Ta content. It has been deduced that the addition of Ta to Ni3Mo alloy causes the V2/V1 to decrease, and by the addition of atoms having an atomic radius larger than that of Mo atoms, the tendency of the formation of the DO22-type ordered phase increases.
(Received April 28, 1978)
* Department of Materials Science and Engineering, Faculty of Engineering, Osaka University, Suita, Osaka 565, Japan.
** Graduate School, Osaka University, Suita, Osaka 565, Japan.
© 2002 The Japan Institute of Metals
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