Microstructural characterization of creep anisotropy at 673 K in the M5® alloy

Rautenberg, Martin; Feaugas, X.; Poquillon, Dominique; Cloué, Jean‐Marc

doi:10.1016/j.actamat.2012.04.001

Cited by 26 publications

(14 citation statements)

References 33 publications

(50 reference statements)

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“…The landscape of curved dislocations pinned at superjogs is identical to that observed post-mortem by Moon et al [16] and Rautenberg et al [21], which again confirms the reliability of in situ experiments. However, and contrary to what has been postulated in reference [16], superjogs do not move by climb, which rules out the interpretation of the plastic properties by the jog-dragging mechanism.…”

Section: Discussionsupporting

confidence: 74%

“…The exact nature of non-prismatic slip (pyramidal or basal) cannot however be unambiguously determined at the fine scale in this specific case. For more extending deviations, ex-situ observations of Rautenberg et al support that the first-order pyramidal plane is the common deviation plane [21].…”

Section: Geometry and Kinetics Of Glide As A Function Of Temperaturementioning

confidence: 88%

“…The tubes were obtained by cold pilgering rolling, followed by heat treatment, inducing a fully recrystallized hexagonal close packed microstructure with a strongly anisotropic crystallographic texture [21]. Grains are isotropic and have a size of 3-5 lm.…”

Section: Methodsmentioning

confidence: 99%

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Dislocation mechanisms in a zirconium alloy in the high-temperature regime: An in situ TEM investigation

2015

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Dislocation mechanisms responsible for the high-temperature mechanical properties of a Zr alloy have been investigated using in situ straining experiments between 250°C and 450°C. At 250°C and 300°C, the results show a steady and homogeneous dislocation motion in prismatic planes, with little cross-slip in the pyramidal and/or basal planes. At 350°C, the kinetics of mobile dislocations becomes very jerky and inhomogeneous, in agreement with a dynamic strain aging mechanism. Above this temperature, the motion is again steady and homogeneous. Extensive crossslip forms super-jogs which are efficient pinning points against the glide motion. These super-jogs move by glide along the Burgers vector direction, never by climb. The glide velocity between super-jogs is linear as a function of the total driving stress (applied stress minus line-tension stress due to dislocation curvature), in agreement with the solute dragging mechanism. The origin of the stress-strain rate dependence with an exponent larger than unity is then discussed.

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Section: Discussionsupporting

confidence: 74%

Section: Geometry and Kinetics Of Glide As A Function Of Temperaturementioning

confidence: 88%

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Dislocation mechanisms in a zirconium alloy in the high-temperature regime: An in situ TEM investigation

2015

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“…In numerous cases, ease of Ti-α and Zr-α to deform plastically in selected crystallographic planes depends on the mobility of the screw dislocation in relation with the core structure of its dislocations. The involvement of the oxygen and the hydrogen atoms and their interactions with the dislocation core are fundamental to solve the thermodynamic processes, which would explain the viscoplastic behaviour and the anisotropy in Ti-α and Zr-α alloys [5][6][7]. We shall go over this last point in the present paper referencing recent experimental work.…”

Section: Introductionmentioning

confidence: 97%

Solute hydrogen and hydride phase implications on the plasticity of zirconium and titanium alloys: a review and some recent advances

Conforto

Guillot

Feaugas

2017

Phil. Trans. R. Soc. A.

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In this contribution, we propose a review of the possible implications of hydrogen on mechanical behaviour of Zr and Ti alloys with emphasis on the mechanisms of plasticity and strain hardening. Recent advances on the impact of oxygen and hydrogen on the activation volume show that oxygen content hinders creep but hydrogen partially screens this effect. Both aspects are discussed in terms of a locking-unlocking model of the screw dislocation mobility in prismatic slip. Additionally, possible extension of this behaviour is suggested for the [Formula: see text] pyramidal slip. The low hydrogen solubility in both Zr and Ti leads in many cases to hydride precipitation. The nature of these phases depends on the hydrogen content and can show crystallographic orientation relationships with the hexagonal compact structure of the alloys. Some advances on the thermal stability of these phases are illustrated and discussed in relation with the deepening of the misfit dislocations. Under tensile loading, we showed that hydrides enhance the hardening process in relation with internal stress due to strain incompatibilities between the Zr and Ti matrix and hydride phases. Different plastic yielding processes of hydrides were identified, which progressively reduce these strain incompatibilities.This article is part of the themed issue 'The challenges of hydrogen and metals'.

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“…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).…”

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confidence: 98%

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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Microstructural characterization of creep anisotropy at 673 K in the M5® alloy

Cited by 26 publications

References 33 publications

Dislocation mechanisms in a zirconium alloy in the high-temperature regime: An in situ TEM investigation

Dislocation mechanisms in a zirconium alloy in the high-temperature regime: An in situ TEM investigation

Solute hydrogen and hydride phase implications on the plasticity of zirconium and titanium alloys: a review and some recent advances

First-Principles Study of Secondary Slip in Zirconium

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