It was recalled that the interactions of moving dislocations with Frank loops in quenched or irradiated materials could result in coalescence or intersection. The latter led to the formation of partial dislocations which were associated with resultant half-loops. The stacking fault energy and specific deformation conditions were shown to control the reaction of partial dislocations with half-loops. A model was proposed for type-II intersections of moving dislocations with Frank loops in irradiated materials. Partial dislocations were formed which lay at the intersections of half-loops and the glide planes of moving dislocations. Two partials were generated for each vacancy loop when one lattice dislocation cut through the loop. Further dislocation intersections in the same glide plane did not result in new partial dislocations. In the case of interstitial loops, a second dislocation intersection created 2 more partials. The first 2 partials formed a dislocation dipole and were separated by one atomic layer. Because the attractive force between the 2 partials of a dipole was large, the break-up energy barrier was high. Break-up could occur when there was an increased spacing between the 2 partials due to continued dislocation intersections on the same slip plane. It could also be brought about by thermal activation and local stress concentration at large strains, or by a high stacking-fault energy. The result of dipole break-up in materials with a high stacking-fault energy was always unfaulting. In the case of low stacking-fault energy materials, the first 2 conditions could lead to the extension of stacking faults and to the formation of twins and an hexagonal close-packed phase; as a result of partial dislocation movement. The unfaulting process appeared to be strongly dependent upon the stacking-fault energy of irradiated materials. The formation of partial dislocations led to an approximately 26% increase in the loop impedance to moving dislocations; above that which had been calculated previously on the basis of elastic interactions between perfect loops and moving dislocations. Because only the first 1 or 2 dislocation intersections generated partial dislocations, this barrier was largely eliminated for sequential intersections in the same slip plane. This was expected to contribute to the channelling effect which was observed in irradiated materials. It was noted that the Burgers vector of the perfect loops which resulted from dislocation intersection was always different to that of moving dislocations. These loops became elongated during continued deformation, until they reacted with other dislocations or until they encountered grain boundaries. Contrary to the case of coalescence reactions, the moving dislocations were not hindered by loops after intersection in low stacking-fault energy materials. Therefore, continued slip could occur in channels, even though the Frank loops were not eliminated.

Formation of Partial Dislocations during the Intersection of Glide Dislocations with Frank Loops in Face-Centered Cubic Lattices. S.G.Song, J.I.Cole, S.M.Bruemmer: Acta Materialia, 1997, 45[2], 501-11