Deformation twin formed by self-thickening, cross-slip mechanism in nanocrystalline Ni

Wu, Xiaolei; Narayan, J.; Zhu, Yuntian

doi:10.1063/1.2949685

Cited by 32 publications

(25 citation statements)

References 30 publications

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“…Dislocation reactions at twin boundaries have been observed both experimentally [2,3,[23][24][25][26][27][28][29][30][31][32] and by molecular dynamics (MD) simulations [33][34][35][36][37][38][39][40][41]. However, no systematic investigation has been reported.…”

Section: Introductionmentioning

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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Section: Introductionmentioning

confidence: 99%

Dislocation–twin interactions in nanocrystalline fcc metals

et al. 2011

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“…12) [6][7][8]23,186,211,212], and deformation twinning [3,[6][7][8]18,23,31,65,66,186,213,214]. In recent years, several new phenomena have been first revealed by experimental investigations, including fivefold twins [8,65,70], twins with reduced macroscopic strain [2], inverse grain size effect on twinning [171], V-shaped twins by a self-thickening mechanism [67,69], and reversible twinning process [215]. Interestingly, a proposed formation mechanism [70] based on the experimentally observations for fivefold twins was later verified by MD simulation [216].…”

Section: Experimental Observationsmentioning

confidence: 99%

“…However, in nc fcc metals, multiple twins often form, which show no obvious plate-like morphology (see Fig. 5b) [34,42,56,[65][66][67][68][69][70]. Under such circumstances, HREM is needed to identify and study the deformation twins.…”

Section: Basics Of Deformation Twinning In Fcc Metalsmentioning

confidence: 99%

Deformation twinning in nanocrystalline materials

Zhu

Liao

2012

Progress in Materials Science

1,175

447

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“…For other twinning modes [15][16][17][18] in hcp and fcc metals where twinning dislocations are well defined, the TBs are coherent and match well the twinning plane on the atomic scale. Hence, it is conceivable that the most common twinning mode in hcp crystals may be controlled by a mechanism other than the widely accepted twinning dislocations.…”

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Twin boundaries showing very large deviations from the twinning plane

Zhang

et al. 2012

Scripta Materialia

152

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In deformation twinning, twin boundaries (TBs) should coincide with the twinning plane. Here we show that the TBs of the most common twinning mode in hexagonal close-packed metals, f1 0 1 2gh1 0 1 1i, may not lie on the f1 0 1 2g twinning plane. Examinations using transmission electron microscopy (TEM) reveal that the TBs in Co and Mg deviate significantly from the f1 0 1 2g plane. High-resolution TEM confirms that the incoherent TBs entirely depart from the twinning plane with a magnitude greater than 45°. Ó 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.Keywords: Twin; Twin boundary; Deformation twinning; Cobalt; Magnesium When crystalline solids are subjected to plastic deformation, in addition to dislocation slip, deformation twinning can be activated to accommodate the microscopic strain. A deformation twin, which predated the concept of dislocation (1934), was defined as "a region of a crystalline body which has undergone a homogeneous shape deformation in such a way that the crystal structure of the resulting product is identical with that of the parent, but oriented differently" [1]. Because the two structures are identical, the boundary plane, also known as the twinning plane, must remain invariant during twinning. The parent and the twin lattices are reflected about the twinning plane.The homogeneous shear involved in twinning carries parent atoms to the twin lattice [2]. To accomplish a homogeneous shear on a twinning plane, passage of twinning dislocations at the interface is required to complete such displacements. A twinning system comprising a twinning plane and a twinning direction along which the shear takes place can be rigorously defined in this scenario. The twin boundary (TB), i.e. the interface between parent and twin, has to coincide with the twinning plane, although microscopically local disregistry is permissible in the presence of twinning dislocation loops. In face-centered cubic (fcc) metals such as aluminum, copper, nickel, etc., the twinning plane is identical to the slip plane of dislocations, i.e. the close-packed {1 1 1} planes, and the twinning dislocations are Shockley partials 1 6 h1 2 1i. In low-symmetry, hexagonal close-packed (hcp) materials such as Mg, which have attracted tremendous attention in the quest for lightweight vehicle design, twinning plays a crucial role in plastic deformation and strain-path anisotropy [3]. On one hand, the easy slip directions contained in the basal plane are incapable of accommodating strain when the unit cell is loaded normal to the basal plane. On the other hand, non-basal slip systems are harder to activate than twinning by at least a factor of 3. The most frequently observed twinning mode in all hcp metals, which is always believed to be on the f1 0 1 2g plane and parallel to the h1 0 1 1 i direction, predominates in plastic deformation among multiple twinning modes. Within the framework of classical deformation theories, numerous crystallographic models have attempted to resolve twinning dislocations on the tw...

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Deformation twin formed by self-thickening, cross-slip mechanism in nanocrystalline Ni

Cited by 32 publications

References 30 publications

Dislocation–twin interactions in nanocrystalline fcc metals

Dislocation–twin interactions in nanocrystalline fcc metals

Deformation twinning in nanocrystalline materials

Twin boundaries showing very large deviations from the twinning plane

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