Dislocation structures in deformed iron single crystals

Abstract

The three-dimensional nature of the dislocation structures in decarburized iron single crystals deformed at 295 K, where three-stage hardening occurred, and at 173 K, where parabolic hardening occurred, has been examined as a function of strain in crystals oriented for slip on the (101)[111] system. At 295 K the dislocation structure is inhomogeneous; in stage I it consists of clusters of primary edge dipoles and a small fraction of secondary dislocations. In stage II, multipolar groups, edge dipole clusters and dislocation networks are aligned along primary slip planes. The secondary and primary dislocation densities are similar.In crystals deformed at 173 K the dislocation structure is uniform and different from that at 295 K. Long, jogged screw dislocations are predominant and there is no apparent alignment of the dislocation structures along primary slip planes.Dislocation structures in deformed crystals containing carbide precipitates show that the main effect of the precipitates are to prevent primary screw dislocations from annihilating at 295 K and to promote secondary slip at both 295 and 173 K.