Determination of the Burgers vector of a dislocation by weak-beam imaging in a HVEM

Abstract

Both the magnitude and the sense of the Burgers vector have been determined exactly from the number of the terminating thickness fringes at the exit of a dislocation from a wedge-shaped foil. Thickness fringes in foils of A1-Mg or Fe-Mn alloys were examined under weak-beam conditions in a 1 MV electron microscope for diffractions up to 211 in the former crystals and 220 in the latter. If the Burgers vector is limited to basic ones, the identification can be made with little tilting of the specimen. The smallness of the tilt angle and the narrowness of the dislocation image allow one to analyse relatively dense dislocation structures. The present technique is recommended as a standard method of determining the Burgers vector in metals and alloys.