55
with the quartz tube during solution heat treating and
aging. The arc melted samples were solution treated at
1315 C for four hours in a tube furnace and water quenched
upon completion of the solution treatment. RSR 185 was
prepared for electron microscopy directly after quenching
(Martin, 1982). Alloy //17 was re-encapsulated, as above,
and subsequently aged in a second tube furnace. The aging
practice is described in Table 3.1. Samples were water
quenched upon completion of aging.
3.3 Characterization: Methods of Analysis
Longitudinal slices were taken from the bar centers
of the extruded RSR alloys and from the center of the
sliced button, alloy //17, mechanically thinned to 130
microns, and jet polished in a solution of 80% methanol,
20% perchloric acid until perforated. The foil for the
RSR 185 alloy was prepared by Martin as described by
Martin (1982). Foils thus prepared were examined in a
Philips 301 Scanning Transmission Electron Microscope
(STEM) and in a special Philips 400 STEM. This latter
microscope is equipped with a field emission gun which
allows small, high intensity beams to be used in the TEM
mode. Special operating features of this microscope are
described in Section 4.1.1 of Chapter 4.
Four different electron diffraction methods were used
to generate the diffraction patterns shown and discussed