Transmission eleotron and field ion microscopy techniques were used to study the nature of short range order (SHO) in as-quenched Ni^o and the ohangee which occur during the very initial stages of the transition to the long range ordered state. Piold ion images of both as-quenohed and alloys aged for very short times below ?50°C show a strong tendency for clustering of well defined groups of atoms about the l<*20> foe poles. The effeot is most pronounced in aged alloys where ordered regions were directly resolved in dark field eleotron micrographs. However, the effect is also observed in the alloyB in which ordered regions are not directly resolved in transmission electron micrographs. The unique orientation dependence of the distribution of the well defined groups of atoms is evidence that the disordered alloy consists of tiny regions possessing a layered type of atomio arrangement in which the Ho concentration is varying on the Ct20) matrix planes.
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