Dislocations in Crystals

Abstract

Transmission electron microscopy is being utilized today in the study of many important problems in materials science and metallurgy. Such areas of research include annealing and heat treating, strengthening, phase transformations and crystal growth. In many of these studies it is important to assemble quantitative data on the dislocation structures existing in the material. These data might include the determination of Burgers vectors ḇ, glide planes and densities of the various dislocations. The purpose of this paper is to review briefly a few of the fundamentals used in obtaining such data.The contrast from a dislocation arises from the extra phase factor α=2πg · Ṟ found in the dynamical equations of electron diffraction, where g is the diffraction vector and Ṟ a vector describing the lattice distortion. For a screw dislocation Ṟ is proportional to ḇ and similarly near the glide plane of an edge dislocation.