Yielding and grain-boundary ledges: Some comments on the Hall-Petch relation

Abstract

Direct observations of grain-boundary ledges have been made in a number of metals and alloys by transmission electron microscopy. Grain-boundary ledges have been observed to be sources of dislocations, and emitted dislocations take on the appearance of pileups. It is suggested that, because of the dearth of observations of dislocation pileups, the pileup concept be reconsidered in the flow-stress-grain-size relationship, and conversely that serious consideration be given to the role of grain-boundary structure, particularly ledges, in determining the mechanical properties of metals and alloys. © 1974 American Institute of Physics.