111


5.1.3 General Microstructural Features


 Alloy RSR 197, as solution heat treated and quenched,

will be used as an example to illustrate some general

microstructural features of all or most of the alloys

described in the chapter.

 The distribution of the gamma prime and its geometry

within each foil is the same for all the alloys to be

described subsequently. Though each gamma prime cuboid

appears to completely penetrate the foil (see, for

example, Figure 5.2b), many in fact do not. The actual

distribution is as described schematically in Figure 5.4.

 In all of the alloys the scale of the microstructure

is very similar. The gamma prime precipitate is

approximately 200 to 300 nm along any edge, and the gamma

generally extends some 20 to 30 nm between the gamma prime

cuboids.

 When the D022 phase is present, the D022 reflections

appear to be shifted with respect to the L12 Ni3Al. There

are two possible explanations for this displacement. Both

are discussed in Section 5.1.4.5.


5.1.4 RSR 197 Aging

5.1.4.1 Solution Heat Treated, Quenched and Aged at
 760 C for up to 100 Hours


 One hour aging at 760 C has produced discreet Ni4Mo

Dla reflections. Figure 5.5a, a B = (100> SAD pattern,