Forward and reverse rearrangements of dislocations in cell walls
We consider the structure and properties of tangled cell walls: interconnected regions of finite thickness in which the dislocation density is high, but across which the misorientation is comparatively low. These are a prominent feature of the substructure of deformed metals, so long as strain, temperature, and stacking-fault energy do not have extremely low or extremely high values. These cell walls have an internal structure, including a polarity, that can be understood on the basis of a statistical/topological model of their original formation. Regardless of how such structures were formed, however, they are metastable and tend to rearrange themselves, under the action of stress, temperature and time, into lower-energy configurations. Some of these rearrangements are possible without the aid of diffusion. The associated glide is not randomly directed and therefore leads to macroscopic strain. The strain is in the same direction as that during the previous straining under which the cell structure was formed (''forward'') in the case of recovery, but it is in the reverse direction upon unloading and reverse loading. In addition to the 'unpiling' of mobile dislocations commonly used to discuss reverse flow, we propose an 'untangling' of stored dislocations which, in the extreme, leads to the observed almost complete disintegration of the 'forward' cell structure at a critical reverse stress. Quantitative considerations lead to an explanation of the observed scaling laws for the Bauschinger effect.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Tokyo Univ. of Agriculture and Technology, Koganei (Japan). Dept. of Mechanical Engineering
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5729907
- Report Number(s):
- LA-UR-85-4231; CONF-860809-2; ON: DE86004728
- Resource Relation:
- Conference: International conference on low-energy dislocation structures, Charlottesville, VA, USA, 10 Aug 1986
- Country of Publication:
- United States
- Language:
- English
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