The alloy aged at 810 C shows almost no change in

strength when aged at this temperature. The D022 phase

was shown to be present in the gamma matrix. Further

characterization of this heat treatment would be necessary

in order to characterize the D022 phase more clearly.

This result is not consistent with order strengthening.

 Aging at 870 C has little or no effect on the

strength. As no strengthening phase precipitates at this

temperature, this is not a surprising result.

 The as-quenched RSR 209 alloy is stronger than the

as-quenched RSR 197 alloy. Apart from the obvious

chemical differences between the two alloys, no other

explanation for this strength difference can be inferred

from any of the observations made in this study. During

the subsequent aging, the alloy, within the time

resolution of testing, loses strength monotonically,

typical of an alloy that is averaging.

 The implications of these observations for alloy

design are significant. The mechanical response of the

RSR 209 to aging is what would be expected of an alloy

that undergoes averaging, a common observation in metals

that are strengthened by fine percipitate. The mechanical

response to aging in RSR 197 aged at 760 C would

presumably represent the effect of ordering. Since it is

possible that the Dla phase is the equilibrium phase for

this aging temperature, it may be possible to fully order