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stages of ordering. In this study the N2M0 existed as a
discreet phase, unlike the N2M0 in the N4M0 aging study,
which Das and Thomas (1974) presume occurred as the result
of the formation of a non-conservative AFB.
Van Tendeloo et al. (1975) have summarized their work
on Ni-2570 Mo alloys and the works of the others as
follows: at 800 C, the N3M0 ordering (decomposition)
follows the sequence FCC SRO DO22  N4M0/N2M0 HCP
- N3M0 orthorhombic. In their work, the DO22 phase forms
only when the quench from solid solution is especially
fast. From this observation they presume that the DO22
phase precedes the precipitation of both the N2M0 and
N4M0 phases, and further, that this DO22 precipitation
was not reported by any of the other previous
investigators because the alloys were not quenched fast
enough in the previous studies. Nevertheless, both the
work of Van Tendeloo et al. (1975) and the work of Das et
al. (1973) show that the stabilization of DO22 at the
N3M0 stoichiometry is especially difficult.
Ni-10% Mo. The first work in an off stoichiometric
alloy was that of Spruiell and Stansbury (1965) who
proposed to have found SRO in their x-ray study of
quenched Ni-10% Mo. The diffuse maxima they detected at
(1, 1/2, 0) positions were retained for aging times of up
to 100 hours at a temperature of 450 C, and though these
maxima sharpened with time, no superlattice ever
developed.