Structural Evaluation of Interfaces by Electron Diffraction

ABSTRACTA method for extracting quantitative information from weak diffraction features at or near matrix reflections is described. The technique requires an accurate knowledge of the fall-off of the matrix reflection. This fall-off was studied both experimentally and theoretically for a wide range of coherence conditions in the microscope. Subtraction of this matrix contribution from the total intensity of an [004] reflection from a E=13 (001) twist boundary shows that the streak arises from local as well as from long range interference effects. The latter contribution varies with spatial coherence length which depends on the condenser setting of the microscope.

Electron Diffraction Applied to the Study of the Structure of (110) Tilt Boundaries in Fe-3% Si

It has become clear in recent years that both low-angle and high-angle grain boundaries can be described in terms of periodic structures. It has also been shown that much useful information concerning the structure of grain boundaries can be obtained by a combination of imaging and electron diffraction in the TEM. In the present study, these techniques are applied to the investigation of grain boundaries in high-purity Fe-3% Si. This material was chosen since very little work has been done to date on the structure of boundaries in bcc materials, and because it was possible to produce nearly pure (110) tilt boundaries with a wide range of angular misorientation in this material by a series of rolling and annealing treatments.The geometry of electron diffraction effects associated with grain boundaries has been extensively described in the literature. In the case of a boundary which is parallel to the electron beam and which has a periodicity present with a direction and a spacing P, a row of spots will occur in reciprocal space at each matrix reflection with a direction and a spacing 1/P.