Fine-scale structural defects in dislocation cores

Abstract

We are now entering what one might consider the third phase of study of dislocations by transmission electron microscopy (TEM). The first phase, in the 1950’s and 1960’s led to classifications of dislocation behavior, concepts of low angle boundaries, equilibrium nodes, and dislocation extension, for example. The second, with the advent of the weak-beam technique, produced improved estimates of stacking fault energy on the basis of dislocation extension, revealed more types of extended dislocation configurations, particularly in ordered intermetallic compounds and inorganic compounds, and revealed finer scale partial dislocations such as misfit dislocations and grain boundary dislocations. With improved resolution for both imaging and direct lattice resolution, we can now be thought to be entering a third phase where information on even finer scale core structure of dislocations might be revealed.The improvement in direct core structure resolution is exciting to those working on the physics of dislocation configurations or on dislocation motion and mechanical properties because of the possibility of direct confirmation of mechanisms and models that have heretofore only been tested by indirect correlations.