142
5.1.5 RSR 209 -- As Solution Heat Treated
and Quenched
Figure 5.20a shows the general microstructural
features of the as-quenched alloy. As in alloy 197, there
are no remnants of the primary gamma prime phase that was
present in the as-extruded microstructure. There is also
cellular gamma prime at the grain boundaries.
Figure 5.20b is a B = \100^ diffraction pattern
showing Pt2Mo reflections and short range order or DO22
reflections. When imaged, the Pt2Mo is very fine. The
Pt2Mo reflections are elongated in 110 directions. This
streaking is consistent with their morphology, a topic to
be dealt with in more detail in Section 5.1.6.2.
5.1.6 RSR 209 Aging
5.1.6.1 Solution Heat Treated. Quenched and Aged
at 760 C for up to 100 Hours
After 10 hours at 760, fine Pt2Mo and fine DO22 phase
have precipitated, as shown in the B = <^100^ diffraction
pattern, Figure 5.21a, and in the dark field images shown
in Figures 5.21b and 5.21c. The diffraction pattern,
Figure 5.21d, taken after 100 hours aging, shows that
N4M0 has formed. The pattern suggests that the N2M0 is
still the dominant phase.