Hirth Lock Research Articles

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

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.

Weak beam Tem studies of composite dislocations in f.c.c. alloys

Single crystals of low stacking fault energy alloys (Cu-10 at.% Al and Cu-15 at. % Al) are strained into stage II. The composite dislocations which play a main role in all the work-hardening theories are examined by weak beam TEM studies. In this way it is possible to reveal their structure as consisting of two stacking fault ribbons on two {111} planes connected by a stair rod partial and bounded by Shockley partials on each plane. Indexing all the partial dislocations shows that most of the composite dislocations are of Lomer-Cottrell type. In connection with the LC dislocations often B4 barriers are formed by the same glide dislocations. Barriers with an obtuse angle between the stacking fault ribbons (Hirth locks) are very rare. Models taking the geometry of all partial dislocations into account give an explanation of the mechanism by which composite dislocations are formed. The experimental results agree with theoretical assumptions (Whelan, 1959) and more recent anisotropic calculations of the structure of these barriers.

Observation of hirth locks in plastically deformed copper single crystals

(1970). Observation of hirth locks in plastically deformed copper single crystals. The Philosophical Magazine: A Journal of Theoretical Experimental and Applied Physics: Vol. 21, No. 172, pp. 857-861.