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Grain rotation mediated by grain boundary dislocations in nanocrystalline platinum.

Wang L, Teng J, Liu P, Hirata A, Ma E, Zhang Z, Chen M, Han X - Nat Commun (2014)

Bottom Line: Grain rotation is a well-known phenomenon during high (homologous) temperature deformation and recrystallization of polycrystalline materials.In recent years, grain rotation has also been proposed as a plasticity mechanism at low temperatures (for example, room temperature for metals), especially for nanocrystalline grains with diameter d less than ~15 nm.Our atomic-scale images demonstrate directly that the evolution of the misorientation angle between neighbouring grains can be quantitatively accounted for by the change of the Frank-Bilby dislocation content in the grain boundary.

View Article: PubMed Central - PubMed

Affiliation: 1] Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China [2].

ABSTRACT
Grain rotation is a well-known phenomenon during high (homologous) temperature deformation and recrystallization of polycrystalline materials. In recent years, grain rotation has also been proposed as a plasticity mechanism at low temperatures (for example, room temperature for metals), especially for nanocrystalline grains with diameter d less than ~15 nm. Here, in tensile-loaded Pt thin films under a high-resolution transmission electron microscope, we show that the plasticity mechanism transitions from cross-grain dislocation glide in larger grains (d>6 nm) to a mode of coordinated rotation of multiple grains for grains with d<6 nm. The mechanism underlying the grain rotation is dislocation climb at the grain boundary, rather than grain boundary sliding or diffusional creep. Our atomic-scale images demonstrate directly that the evolution of the misorientation angle between neighbouring grains can be quantitatively accounted for by the change of the Frank-Bilby dislocation content in the grain boundary.

No MeSH data available.


Related in: MedlinePlus

HRTEM images show the intra-grain dislocations in larger grains.(a) Full dislocation (marked with ‘T’) in a ~11-nm-sized grain. (b) Partial dislocations resulting in stacking faults (as noted by the arrows) in an ~7-nm-sized grain. Scale bars, 2 nm.
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f5: HRTEM images show the intra-grain dislocations in larger grains.(a) Full dislocation (marked with ‘T’) in a ~11-nm-sized grain. (b) Partial dislocations resulting in stacking faults (as noted by the arrows) in an ~7-nm-sized grain. Scale bars, 2 nm.

Mentions: For larger grains, on loading we frequently observed movements and interactions of cross-grain dislocations. Figure 5a provides a typical HRTEM observation of full dislocation (marked with ‘T’) in a ~11-nm-sized grain, with a Burgers vector of a/2[011]. For d between 6 and 10 nm, full dislocations become much less, and stacking faults resulting from the passage of partial dislocations (as noted by the arrows in Fig. 5b) become more frequent. In fact, >100 grains (with d from 3 to ~25 nm) were monitored during and at the end of the pulling. These include 48 in situ examples, and the others are ex-situ ones (see the many examples in Supplementary Figs 2–11). There is a clear trend with decreasing d: the dislocations in action transition from full to partial inside the grains, and eventually to those in the GB to mediate grain rotation. The mechanisms are depicted schematically in Supplementary Fig. 12. The former (cross-grain dislocation) mechanism has been treated in many previous studies, so our data in that regard are only displayed in Supplementary Materials for interested readers.


Grain rotation mediated by grain boundary dislocations in nanocrystalline platinum.

Wang L, Teng J, Liu P, Hirata A, Ma E, Zhang Z, Chen M, Han X - Nat Commun (2014)

HRTEM images show the intra-grain dislocations in larger grains.(a) Full dislocation (marked with ‘T’) in a ~11-nm-sized grain. (b) Partial dislocations resulting in stacking faults (as noted by the arrows) in an ~7-nm-sized grain. Scale bars, 2 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4109021&req=5

f5: HRTEM images show the intra-grain dislocations in larger grains.(a) Full dislocation (marked with ‘T’) in a ~11-nm-sized grain. (b) Partial dislocations resulting in stacking faults (as noted by the arrows) in an ~7-nm-sized grain. Scale bars, 2 nm.
Mentions: For larger grains, on loading we frequently observed movements and interactions of cross-grain dislocations. Figure 5a provides a typical HRTEM observation of full dislocation (marked with ‘T’) in a ~11-nm-sized grain, with a Burgers vector of a/2[011]. For d between 6 and 10 nm, full dislocations become much less, and stacking faults resulting from the passage of partial dislocations (as noted by the arrows in Fig. 5b) become more frequent. In fact, >100 grains (with d from 3 to ~25 nm) were monitored during and at the end of the pulling. These include 48 in situ examples, and the others are ex-situ ones (see the many examples in Supplementary Figs 2–11). There is a clear trend with decreasing d: the dislocations in action transition from full to partial inside the grains, and eventually to those in the GB to mediate grain rotation. The mechanisms are depicted schematically in Supplementary Fig. 12. The former (cross-grain dislocation) mechanism has been treated in many previous studies, so our data in that regard are only displayed in Supplementary Materials for interested readers.

Bottom Line: Grain rotation is a well-known phenomenon during high (homologous) temperature deformation and recrystallization of polycrystalline materials.In recent years, grain rotation has also been proposed as a plasticity mechanism at low temperatures (for example, room temperature for metals), especially for nanocrystalline grains with diameter d less than ~15 nm.Our atomic-scale images demonstrate directly that the evolution of the misorientation angle between neighbouring grains can be quantitatively accounted for by the change of the Frank-Bilby dislocation content in the grain boundary.

View Article: PubMed Central - PubMed

Affiliation: 1] Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China [2].

ABSTRACT
Grain rotation is a well-known phenomenon during high (homologous) temperature deformation and recrystallization of polycrystalline materials. In recent years, grain rotation has also been proposed as a plasticity mechanism at low temperatures (for example, room temperature for metals), especially for nanocrystalline grains with diameter d less than ~15 nm. Here, in tensile-loaded Pt thin films under a high-resolution transmission electron microscope, we show that the plasticity mechanism transitions from cross-grain dislocation glide in larger grains (d>6 nm) to a mode of coordinated rotation of multiple grains for grains with d<6 nm. The mechanism underlying the grain rotation is dislocation climb at the grain boundary, rather than grain boundary sliding or diffusional creep. Our atomic-scale images demonstrate directly that the evolution of the misorientation angle between neighbouring grains can be quantitatively accounted for by the change of the Frank-Bilby dislocation content in the grain boundary.

No MeSH data available.


Related in: MedlinePlus