Dislocation–twin interactions in nanocrystalline fcc metals

Abstract

Dislocation interaction with and accumulation at twin boundaries have been reported to significantly improve the strength and ductility of nanostructured face-centered cubic (fcc) metals and alloys. Here we systematically describe plausible dislocation interactions at twin boundaries. Depending on the characteristics of the dislocations and the driving stress, possible dislocation reactions at twin boundaries include cross-slip into the twinning plane to cause twin growth or de-twinning, formation of a sessile stair-rod dislocation at the twin boundary, and transmission across the twin boundary. The energy barriers for these dislocation reactions are described and compared.

Controllable fatigue cracking mechanisms of copper bicrystals with a coherent twin boundary

“…So the TB shows higher fatigue cracking resistance than high-angle GB and the fatigue crack nucleates along the SB like in single crystals 3,5 . Whereas in the bicrystal with the TB perpendicular to the loading direction, the S3 SBs would pile up at the TB and could also penetrate through the TB partially 34 . The difference between the O of corresponding S3 slip systems in both the component grains is low, which generates high opportunity of dislocation penetration and good strain compatibility at the TB 21,22 .…”

The dual role of coherent twin boundaries in hydrogen embrittlement

“…In the case of CTBs, such sliding may occur by dislocation glide along the GB plane, that is, by the conventional dislocation-based mechanism of plastic deformation [28][29][30][31] . Dislocation-mediated GB sliding is possible at CTBs because the GB plane of a CTB is a {111} plane, that is, a glide plane for dislocations in FCC metals 32 .…”

Strengthening at nanoscaled coherent twin boundary in f.c.c. metals

“…metals such as Al and Ni [12,13], which have much higher stacking fault energies than Cu. Crystallographic analysis and MD simulation showed various reactions at TB for impinging screw and non-screw dislocations [4,5,14]. Therefore, the study of slip transfer in nanotwinned Al (nt-Al) and nanotwinned Ni (nt-Ni) is important to understand their deformation behaviour for enhancing strength and preserving ductility.…”