2.2.5 Ordering Reactions and Kinetics....31
 2.2.5.1 Binary Alloys.............31
 2.2.5.2 Ternary Alloys ...........35
 2.2.6 Ni-Al Ni3A1.....................36

 2.3 Diffraction Patterns: NixMo Phases/
 Ni3Al .....................................40

 2.3.1 DO22 Reciprocal Lattice............40
 2.3.2 Dla/Pt2Mo/L12 Reciprocal Lattices..42
 2.3.3 SRO (1, 1/2, 0) Scattering.........46
 2.3.4 Variant Imaging...................46
 2.3.4.1 DO22: Ni3Mo...............47
 2.3.4.2 Dla: Ni4Mo.................47
 2.3.4.3 Pt2Mo: Ni2Mo..............51

3 EXPERIMENTAL PROCEDURE........................ 53

 3.1 Composition............................ .. 53

 3.2 Heat Treatments.......................... 54

 3.3 Characterization: Methods of Analysis....55

4 SPECIAL METHODS................................. 61

 4.1 Convergent Beam Electron Diffraction
 (CBED) Methods............................61

 4.1.1 Experimental Technique.............. 63
 4.1.2 HOLZ Lines (High Order Laue
 Zone Lines)........................ 66
 4.1.3 Indexing HOLZ Lines................ 72
 4.1.4 Lattice Parameter Changes...........89
 4.1.5 The Effect of Strain and
 Non-Cubicity on Pattern Symmetry...91

 4.2 Energy Dispersive Methods.................97

5 RESULTS ...................... .............. 106

 5.1 Microstructural Characterization.........106

 5.1.1 As Extruded RSR 197 and RSR 209
 Alloys............................ .106
 5.1.2 RSR 197-As Solution Heat Treated
 and Quenched......................106
 5.1.3 General Microstructural Features..111
 5.1.4 RSR 197 Aging....................111
 5.1.4.1 Solution Heat Treated,
 Quenched and Aged at
 760 C for up to 100
 Hours.................... 111