Dislocation core structure and dynamics in two atomic models of α-zirconium

Khater, Hassan A.; Bacon, D. J.

doi:10.1016/j.actamat.2010.01.028

Cited by 53 publications

(53 citation statements)

References 27 publications

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“…Our results reveal a strong tendency towards dislocation dissociation into Shockley partials separated by wide regions of fcc-like stacking fault, in analogy to what occurs in solid helium. We find that the Peierls stress for the glide of edge dislocations in the hcp basal plane amounts to ∼1 MPa, which is very similar in magnitude to the values reported for classical metals with the hcp structure (e.g., Zr and Cd) [12,13]. However, in contrast to other classical solids but in analogy to solid helium, edge dislocations in hcp rare gases turn out to be extremely mobile: they can diffuse with an approximate velocity of 50 m/s in the absence of any applied stress at temperatures as low as 25 K (that is, well below the corresponding Debye temperature Θ D ∼ 65 K [16]).…”

Section: Introductionsupporting

confidence: 69%

“…For instance, Landinez-Borda et al have shown that in solid helium either screw or edge dislocations with Burgers vectors contained in the hcp basal plane tend to dissociate into Shockley partial dislocations separated by ribbons of fcc-like stacking fault [11]. The same behavior is observed in classical metals with the hcp structure like, for instance, Zr [2,12,13]. Nevertheless, since the nature of the atomic interactions in rare gases and metallic systems are so different, the physical origins of such similarities (or the differences explained above) are not totally understood.…”

Section: Introductionsupporting

confidence: 51%

“…The shortest perfect Burgers vector in an hcp lattice is b = 1 3 1120 , and the most common dislocation slip planes are the basal, (0001), and prism, {1010}, planes [2,12,25]. The preference of the glide plane is determined by the energy and stability of a stacking fault.…”

Section: Edge Dislocation Structurementioning

confidence: 99%

“…We can quantify the spread of such a disregistry through the distribution of partial Burgers vector components, [b x , b y ], within the glide plane [12,22]. These partial components can be expressed as:…”

Section: Differential Displacement Analysis (Dd)mentioning

confidence: 99%

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Dislocation Structure and Mobility in Hcp Rare-Gas Solids: Quantum versus Classical

et al. 2018

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Abstract:We study the structural and mobility properties of edge dislocations in rare-gas crystals with the hexagonal close-packed (hcp) structure by using classical simulation techniques. Our results are discussed in the light of recent experimental and theoretical studies on hcp 4 He, an archetypal quantum crystal. According to our simulations classical hcp rare-gas crystals present a strong tendency towards dislocation dissociation into Shockley partials in the basal plane, similarly to what is observed in solid helium. This is due to the presence of a low-energy metastable stacking fault, of the order of 0.1 mJ/m 2 , that can get further reduced by quantum nuclear effects. We compute the minimum shear stress that induces glide of dislocations within the hcp basal plane at zero temperature, namely, the Peierls stress, and find a characteristic value of the order of 1 MPa. This threshold value is similar to the Peierls stress reported for metallic hcp solids (Zr and Cd) but orders of magnitude larger than the one estimated for solid helium. We find, however, that in contrast to classical hcp metals but in analogy to solid helium, glide of edge dislocations can be thermally activated at very low temperatures, T∼10 K, in the absence of any applied shear stress.

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Section: Introductionsupporting

confidence: 69%

Section: Introductionsupporting

confidence: 51%

Section: Edge Dislocation Structurementioning

confidence: 99%

Section: Differential Displacement Analysis (Dd)mentioning

confidence: 99%

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Dislocation Structure and Mobility in Hcp Rare-Gas Solids: Quantum versus Classical

et al. 2018

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“…We also performed atomistic simulations with the embedded atom method (EAM) potential developed by Mendelev and Ackland [22] to check the validity of our results in larger simulation cells. This potential is suitable to model screw dislocations, predicting, in particular, dissociation in a prismatic plane [23], in contrast with most other empirical potentials. The cells are fully periodic and contain a dislocation dipole with a periodic quadrupolar arrangement, described as an S arrangement in a previous paper [11].…”

mentioning

confidence: 99%

First-Principles Study of Secondary Slip in Zirconium

2014

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Although the favored glide planes in hexagonal close-packed Zr are prismatic, screw dislocations can escape their habit plane to glide in either pyramidal or basal planes. Using ab initio calculations within the nudged elastic band method, we show that, surprisingly, both events share the same thermally activated process with an unusual conservative motion of the prismatic stacking fault perpendicularly to itself. Halfway through the migration, the screw dislocation adopts a nonplanar metastable configuration with stacking faults in adjacent prismatic planes joined by a two-layer pyramidal twin.Plastic deformation in metals results mainly from the motion of line defects called dislocations. Many dislocation properties derive from the atomic-scale structure of their core, the region in the immediate vicinity of the dislocation line where crystallinity is disrupted. One such property is cross slip, i.e., the ability for screw dislocations to change glide plane, a stress-releaving process central to strain hardening and fatigue resistance [1,2].Thus far, cross slip has mostly been studied in facecentered cubic (fcc) metals for the conventional planar dissociated 1/2 110 {111} dislocations. Elasticity models [2,3] confirmed by atomic-scale simulations [4,5] showed that the dominant cross-slip mechanism involves a local constriction of the dislocation in its initial glide plane followed by redissociation in the crossslip plane (Friedel-Escaig mechanism). Another mechanism, which occurs under higher stresses met, for instance, in nanocrystalline plasticity [6], involves the successive change of glide plane of both partial dislocations [7]. Mechanisms involving a metastable configuration of the screw dislocation spread over several planes are also possible, as found in iridium [8].Cross slip is also observed in hexagonal close-packed (hcp) metals. In zirconium and titanium, 1/3 1210 dislocations are dissociated and glissile in prismatic {1010} planes [9], as confirmed by first-principles calculations [10,11]. But screw dislocations have also been reported experimentally to glide at high temperatures in both first-order pyramidal π 1 {1011} planes [12][13][14] and basal {0001} planes [12, 15] (see Fig. 1 for a graphical description of these planes). These secondary-slip processes do not correspond to cross slip as understood in fcc metals because the parent and the cross-slipped glide planes are not equivalent. Rather, this secondary slip in hcp metals is related to the fundamental question: how can a dislocation dissociated in a plane glide in another plane?In this Letter, we employ a combination of firstprinciples and empirical potential atomic-scale calculations to study secondary slip in hcp metals. We focus mainly on zirconium, although we checked that the present findings also apply to titanium. We show that unexpectedly, both basal and pyramidal slips are limited by the same thermally activated process, which involves an unusual motion of the prismatic stacking fault perpendicularly to itself, and results in a no...

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First Order Pyramidal Slip of $$1/3\ \langle 1\bar{2}10\rangle $$ Screw Dislocations in Zirconium

Chaari

Clouet

Rodney

2014

Metall Mater Trans A

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Atomistic simulations, based either on an empirical interatomic potential or on ab initio calculations, are used to study the pyramidal glide of a 1/3 1210 screw dislocation in hexagonal close-packed zirconium. Generalized stacking fault calculations reveal a metastable stacking fault in the first order pyramidal {1011} plane, which corresponds to an elementary pyramidal twin. This fault is at the origin of a metastable configuration of the screw dislocation in zirconium, which spontaneously appears when the dislocation glides in the pyramidal plane.

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Dislocation core structure and dynamics in two atomic models of α-zirconium

Cited by 53 publications

References 27 publications

Dislocation Structure and Mobility in Hcp Rare-Gas Solids: Quantum versus Classical

Dislocation Structure and Mobility in Hcp Rare-Gas Solids: Quantum versus Classical

First-Principles Study of Secondary Slip in Zirconium

First Order Pyramidal Slip of $$1/3\ \langle 1\bar{2}10\rangle $$ Screw Dislocations in Zirconium

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