152
Figure 5.26c, a B = <^111^> selected area diffraction
pattern, shows no Pt2Mo 1/3 220 reflections.
5.1.6.4 Aging Summary -- RSR 209
Aging at the lowest temperature produces a mixture of
N2M0 Pt2Mo, DO22 N3M0, and after 100 hours, Da N4M0
phase. These first two phases coarsen during aging, as
would be expected. At 810 C, platelets of Pt2Mo N2M0 and
presumably DO22 phase as well, are present. The Pt2Mo
coarsens considerably during aging. An intercuboidal
phase precipitates prior to the 100 hour treatment. A
morphologically similar phase, identified by electron and
x-ray diffraction pattern analysis of the 870 C aged
sample, is shown to be alpha Mo. An interfacial
dislocation network has developed after 1 hour at 810 C.
Aging at 870 C merely accelerates the coarsening of
those phases that precipitate at 810 C. Pt2Mo is
initially present after one hours aging but has
disappeared after 100 hours. An intercuboidal phase,
identified as Mo from both x-ray and electron diffraction
patterns is predominant in the intercuboidal regions. An
interfacial dislocation structure is present after only
one hours aging. Whenever a grain boundary could be
imaged, this grain boundary invariably contained cellular
gamma prime, sometimes decorated with a phase identified
as NiMo.