ORDERING IN RAPIDLY SOLIDIFIED NI2MO

The lack of experimental work on ordering transformations in Ni//2Mo is presumably due to the difficulty in obtaining a single phase fcc alloy of this composition. Enhanced solid solubility of Mo in Ni which accompanies rapid solidification processing (RSP) makes the formation of such a phase possible. The Ni//3Mo alloy has been reported to decompose into a mixture of the Ni//4Mo (D1//a) and the Ni//2Mo (Pt//2Mo) ordered structures. A secondary tendency for the formation of the stoichiometric DO//2//2 structure becomes evident on prolonged ageing or during electron irradiation in the temperature range 475-650 K in the Ni//3Mo alloy. With this background in mind the ordering processes in the Ni//2Mo alloy have been examined.