INTERPRETATION OF ELECTRON DIFFRACTION PATTERNS FROM THIN PLATELETS.

Electron diffraction patterns from foils containing planar defects, e.g., precipitates or stacking faults, are considered in terms of relrods normal to the plane of the defect, andor normal to the specimen surface. The patterns can be regarded as consisting of streaked reciprocal lattices superimposed on the matrix lattice. In the materials examined, faulting did not reproduce any detectable physical shift of allowed reflections. The observations indicate that faulting is regular rather than random. Stacking faults and HCP precipitates in FCC crystals can not as a rule be distinguished in the early stages of formation of the precipitate. A complete analysis of the spot pattern from foils containing planar defects generally requires an accurate determination of the crystal orientation. For this purpose Kikuchi patterns provide sufficient accuracy and an assessment of this is made. Author