Stages in the Recovery of Deformed Single Crystals of Iron Studied by Position Annihilation Techniques

Isochronal as well as isothermal measurements have been made on high purity single crystals of iron which had been cold rolled about 10% prior to annealing. Two steps were isolated corresponding first to the annihilation of screw dislocations and then to the elimination of edge dislocations at higher temperatures. A method was developed for analyzing the isochronal annealing data to yield the activation energies. A second-order reaction earlier proposed was used and confirmed; the isothermal data were inconsistent with other reaction orders. The reaction rate near 673 K deduced from isochronal experiment was found to be in excellent agreement with the isothermal rate. However, at intermediate temperatures the agreement of rates was poor. The two activation energies for edge and screw processes were small compared with the activation energy for self-diffusion. They were consistent with that for thermally activated dislocation mobility.