Formation mechanism of wide stacking faults in nanocrystalline Al

Liao, Xiaozhou; Srinivasan, S.; Zhao, Yaohua; Baskes, M. I.; Zhu, Yuntian; Zhou, Feng; Lavernia, Enrique J.; Xu, Haiyue

doi:10.1063/1.1734689

Cited by 195 publications

(94 citation statements)

References 20 publications

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“…Conversely, slip occurs in CG or NG materials when a lead partial dislocation is followed by a trailing partial dislocation on the same {111} plane 15 . A difference between CG metals and NG metals is that in NG metals the boundaries supply the partial dislocations needed for slip or twinning 1,2,4,18,19 . Molecular dynamics has shown that grain boundaries and even pristine phase boundaries can nucleate partial dislocations into Cu 33,34 .…”

Section: Resultsmentioning

confidence: 99%

“…This nucleation mechanism permits several intersecting twins to form, potentially adversely affecting fracture behaviour 16,17 . Conversely, in NG metals, twins nucleate predominantly from reactions within grain boundaries 1,2,4,18,19 . With twins formed in this way, several desirable properties emerge, such as high strength, hardness, ductility and thermal stability, not seen in the CG counterparts 11 .…”

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confidence: 99%

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The critical role of grain orientation and applied stress in nanoscale twinning

McCabe¹,

Beyerlein

Carpenter³

et al. 2014

Nat Commun

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Numerous recent studies have focused on the effects of grain size on deformation twinning in nanocrystalline fcc metals. However, grain size alone cannot explain many observed twinning characteristics. Here we show that the propensity for twinning is dependent on the applied stress, grain orientation and stacking fault energy. The lone factor for twinning dependent on grain size is the stress necessary to nucleate partial dislocations from a boundary. We use bulk processing of controlled nanostructures coupled with unique orientation mapping at the nanoscale to show the profound effect of crystal orientation on deformation twinning. Our theoretical model reveals an orientation-dependent critical threshold stress for twinning, which is presented in the form of a generalized twinnability map. Our findings provide a newfound orientation-based explanation for the grain size effect: as grain size decreases the applied stress needed for further deformation increases, thereby allowing more orientations to reach the threshold stress for twinning.

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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

The critical role of grain orientation and applied stress in nanoscale twinning

McCabe¹,

Beyerlein

Carpenter³

et al. 2014

Nat Commun

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“…where E b is the energy per unit length of a dislocation with a Burgers vector is at an angle b to the dislocation line, G is the shear modulus, m is the Poisson's ratio, R can be estimated as the grain size d, and r 0 can be estimated as the Burgers vector b [44]. Eq.…”

Section: Cross-slip Of the 30°partial At The Twin Boundarymentioning

confidence: 99%

Dislocation–twin interactions in nanocrystalline fcc metals

et al. 2011

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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.

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“…The formation of L-C locks also needs the participation of stacking faults. NC materials are known to produce wider stacking faults than their coarsegrained counterparts, especially near the grain boundaries [24,25], and therefore should be more favorable to producing L-C locks. Since the cross-slip of perfect dislocations occurs more readily near grain boundaries, where stress concentrations exist [23], there should be higher density of L-C locks, and consequently higher dislocation accumulation near grain boundaries.…”

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confidence: 99%

Strong Strain Hardening in Nanocrystalline Nickel

et al. 2009

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Low strain hardening has hitherto been considered an intrinsic behavior for most nanocrystalline (NC) metals, due to their perceived inability to accumulate dislocations. In this Letter, we show strong strain hardening in NC nickel with a grain size of $20 nm under large plastic strains. Contrary to common belief, we have observed significant dislocation accumulation in the grain interior. This is enabled primarily by Lomer-Cottrell locks, which pin the lock-forming dislocations and obstruct dislocation motion. These observations may help with developing strong and ductile NC metals and alloys.

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Formation mechanism of wide stacking faults in nanocrystalline Al

Cited by 195 publications

References 20 publications

The critical role of grain orientation and applied stress in nanoscale twinning

The critical role of grain orientation and applied stress in nanoscale twinning

Dislocation–twin interactions in nanocrystalline fcc metals

Strong Strain Hardening in Nanocrystalline Nickel

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