A static and dynamic electron microscope study of slip propagation across grain boundaries in polycrystalline metals

Abstract

The deformation of polycrystalline metals proceeds by the movement of individual dislocations both within the grains and across the grain boundaries which separate them. It is therefore apparent that these grain boundaries have an important role in controlling the mechanical properties of materials. It is known, for example, that the yield stress is directly affected by the density of grain boundaries in a metal; in the familiar Hall—Petch relationship it is inversely proportional to the grain diameter. Various models have been proposed to account for this behaviour, all of which involve the interaction between dislocations and grain boundaries (for a review see e.g. ref. 1). Microscopically, these interactions can be accomplished by one of several different mechanisms, such as the nucleation of new dislocations, direct transmission of dislocations across the interface, the absorption and desorption of dislocations into and out of the interface, among others.