phases is demonstrated by simultaneously imaging the

lattices of the two phases at common interfaces. The

predominant NixMo precipitate in the W bearing quaternary

is Pt2Mo (Ni2Mo), though D022 and Dla can be present

concurrent with the Pt2Mo.

 When aged at temperatures above the solvi for the

NixMo phases, equilibrium NiMo and equilibrium Mo phases

precipitate, the former in the Ta containing alloy, the

latter in the W containing alloy. The presence of these

phases is in general agreement with the expected phase

equilibria predicted by the phase diagram.

 Convergent beam electron diffraction, one of the

methods used in the characterization of the alloys, is

shown to have sufficient sensitivity for lattice parameter

variations to qualitatively measure the difference in

partitioning of the quaternary additions to the gamma

prime and gamma phases of both quaternary alloys. The

method is compared to x-ray diffraction results and

confirmed by energy dispersive x-ray analysis. In

addition to the measurement of partitioning, the fine

spatial resolution of the convergent beam method makes it

ideal for the measurement of other factors that are

reflected in lattice parameter changes -- strain, for

example. Simple equations are developed for the indexing

of HOLZ line patterns and for the measurement of lattice

parameters and uniform strain. Examples are given using

the superalloys characterized in this study.


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