Dislocation self-organization under single slip straining and dipole properties

Abstract

Spontaneous microstructural organization under single slip is investigated by transmission electron microscopy. The formation and the structure of dislocation entanglements are analyzed on three types of fcc-based systems, Al, Cu and TiAl, all deformed by 〈1 1 0〉 {1 1 1} slip. Differences are found that depend on stacking fault energy and lattice friction. The importance of dipolar configurations is outlined. Selected properties of dipoles are analyzed theoretically under isotropic and anisotropic elasticity in cubic systems. At variance from screw and near-screw dipoles, the stress-free equilibrium angle of an edge dipole is little dependent on the material's elastic anisotropy. In Cu, for instance, a screw dipole is at equilibrium at around 59° from the slip plane, and this angle is unchanged over a range of dislocation characters of approximately ±20°. On the other hand, given a dipole height, the passing stress is a maximum in the screw orientation. It is, however, not a minimum in the edge orientation. Static and dynamic dipole properties are but little affected by dissociation down to a dipole height of the order of a few times the dissociation distance.