5
differences, chemistries aside, between the Ni-Mo binaries
and Ni-Mo-Al-(x) alloys, most importantly the presence in
the ternaries and quaternaries of primary gamma prime
phase. Could this gamma prime phase affect the
precipitation behavior of the Nix(Mo,x) phases which
precipitate from gamma solution? Would the physical
constraints imposed by the gamma prime precipitate affect
the "equilibrium" structure of these precipitates after
coarsening? What would be the effect of the quaternary
additions on the metastable precipitation behavior of
these alloys? Would these quaternary additions have any
effect on the gamma prime phase?
In order to answer questions such as these, it was
necessary to characterize the Pratt and Whitney alloys in
a way that such information could be directed towards
answering these questions. The study was to focus on the
use of the electron microscope. The advantage offered by
this instrument in studying fine scale precipitation
phenomena are trivially obvious, copiously documented, and
relatively straightforward. Some microstructural
measurements, however, are not easily accomplished in the
microscope -- the measurement of local composition or the
measurement of local lattice parameters, for example.
These applications were in their infancy and had, for the
most part, not as yet been directed toward practical
problem solving in materials science.