Abstract
We investigate the mechanisms of incipient plasticity at low angle twist and asymmetric tilt boundaries in fcc metals. To observe plasticity of grain boundaries independently of the bulk plasticity, we simulate nanoindentation of bicrystals. On the low angle twist boundaries, the intrinsic grain boundary (GB) dislocation network deforms under load until a dislocation segment compatible with glide on a lattice slip plane is created. The half loops are then emitted into the bulk of the crystal. Asymmetric twist boundaries considered here did not produce bulk dislocations under load. Instead, the boundary with a low excess volume nucleated a mobile GB dislocation and additional GB defects. The GB sliding proceeded by motion of the mobile GB dislocation. The boundary with a high excess volume sheared elastically, while bulk-nucleated dislocations produced plastic relaxation.
Highlights
Grain boundaries (GB) play an important role in the plastic deformation of polycrystalline metals [1]
Low angle twist boundaries can be a source of lattice dislocations
Lattice dislocations are generated from intrinsic GB dislocation network
Summary
Grain boundaries (GB) play an important role in the plastic deformation of polycrystalline metals [1]. Bomarito et al [20] performed a quantitative investigation of strength (independent of mechanism) of twist GBs in aluminum, and found that no usual grain boundary. To elucidate of agrain boundaries with minimal interaction with dislocation dislocation occurs only fornanoindentation a dense GB (lowin excess volume)of and that it is accompanied by nucleation structures, we simulate the vicinity the grain boundary. Such a loading of lattice partials which create short stacking faults adjacent to the boundary. The practical value of CSP comes from its ability to distinguish lattice defects from regions that underwent large homogeneous elastic deformations as well as from its ability to separate different defect types (e.g., dislocation cores, stacking faults, GBs)
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