Electron microscope studies of grain boundary dislocation behavior

Abstract

A review is given of various grain boundary dislocation (GBD) phenomena which have been observed during the last few years in thin-film bicrystal specimens containing grain boundaries possessing different controlled geometries. All of the observations were made by transmission electron microscopy using gold bicrystals which were prepared by welding thin single-crystal films together face-to-face under predetermined conditions. The review begins with a discussion of a number of formal geometrical aspects of GBD's which constitutes a necessary background for the description of the experimental results. Experimental determinations of the equilibrium GBD structure of a variety of twist, tilt and mixed low and high angle grain boundaries are then described. Following this, a number of observations of grain boundaries containing excess non-equilibrium GBD's are presented. Several observations involving GBD behavior during plastic straining and GBD climb phenomena during the exposure of grain boundaries to non-equilibrium point defect concentrations are then discussed. Finally, some comments are made about possible grain boundary migration mechanisms.