Dissociated structure of dislocation loops with Burgers vectora〈100〉 in electron-irradiated Cu-Ni

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Abstract
The rectangular dislocation loops with total Burgers vector a〈100〉 which are formed in Cu-Ni alloys during 1 MeV electron irradiation at elevated temperatures have been examined by weak-beam electron microscopy. The loop edges were found to take up a Hirth-lock configuration, dissociating into two Shockley partials and one a/3〈100〉 stair-rod dislocation. This explains the topography and the practical stability of the loops. Computer-simulated images of loops with the proposed structure agree with the experimental images. The behaviour of the rectangular loops seems to exclude the possibility that the Hirth lock can be an efficient barrier to dislocation motion.