PRODUCTION OF CO-NI ALLOYS BY MECHANICAL-ALLOYING

Co-Ni solid solutions, such as Co30Ni70, Co40Ni60, Co50Ni50, Co60Ni40 and Co70Ni50 alloys, have been produced by mechanical-alloying using C o and Ni powders prepared in our laboratory by the polyol process as m etallic precursors. The grinding transforms the hexagonal Co phase int o a cubic Co phase by stacking fault creation and permits a possible m utual diffusion of Co and Ni species in the two f.c.c. phases. The res ulting powder alloys are nanocrystalline with a high atomic-level of i nternal strain. Magnetic data on these powders shows behaviour typical of a soft ferromagnetic alloy. A strong influence of oxygen contamina tion on magnetic properties of these alloys was observed, mainly on th e saturation magnetization which decreases with increasing oxygen cont ent.