The relation between ductility and stacking fault energies in Mg and Mg–Y alloys

Sandlöbes, Stefanie; Friák, Martin; Zaefferer, Stefan; Dick, A.; Yi, Sangbong; Letzig, Dietmar; Pei, Zongrui; Zhu, Li; Neugebauer, Jörg; Raabe, Dierk

doi:10.1016/j.actamat.2012.02.006

Cited by 494 publications

(182 citation statements)

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“…Similarly, a change in mechanisms with addition of yttrium was observed under dynamic high strain rate experiments [19]. phenomena such as formation of stable yttrium oxides at grain boundaries [43,44,78], increased forest dislocation based hardening [11,20,21,42], or large grain boundary yttria and precipitate denuded zones near the grain boundaries causing material softening.…”

Section: Discussionmentioning

confidence: 99%

“…The improvement in mechanical behavior reported to be due to some combination of the following phenomena: the activation of <c+a> dislocations [11,20,21,42], forest dislocation hardening [18], inhabitance of the static recrystallization [14], and formation of an enhanced oxide film [43,44]. In this paper, we reveal and elucidate the high-temperature deformation behavior and mechanisms of nanocrystalline magnesium with and without yttrium for a temperature range of 573 K to 723 K under constant stress loadings.…”

Section: Discussionmentioning

confidence: 99%

“…Evidence for the occurrence of enhanced grain-boundary shearing with addition of yttrium suggests that the diffusion creep must be accompanied by grain-boundary sliding. Moreover, yttrium has a softening effect on the sliding of boundaries which suggests that the experimentally observed high temperature beneficial effects of yttrium addition could be attributed to some other mechanisms or phenomena such as formation of stable yttrium oxides at grain boundaries [43,44,78], increased forest dislocation based hardening [11,20,21,42], or large grain boundary yttria and precipitate denuded zones near the grain boundaries causing material softening. Furthermore, it has been experimentally shown that in aged Mg-Y alloys, due to a supersaturated solid-solution state within the grains, dynamic precipitation (two pseudoequilibrium phases) can occur during creep [18,26,27].…”

Section: E Effect Of Yttrium On the Grain Boundary Slidingmentioning

confidence: 99%

“…Since magnesium has a hexagonal close packed (hcp) structure, it has a limited number of active slip systems at room temperature [8,9] which leads to failure in polycrystalline Mg-alloys at ambient conditions before dislocation glide can occur [10][11][12]. In an effort to overcome these low strength shortcomings, recent studies have considered the effects of adding certain alloying elements to magnesium, such as Al-Zn, Al-Si, Al-Ca, Al-Sr, Sn-Ca, Zr-Y, and minute traces of other rare-earth (RE) elements [6,[13][14][15][16][17][18][19][20][21][22][23]. The objective of all these studies has been to qualitatively identify the principles governing solute and precipitate strengthening and ductility while improving manufacturability, as well as lowering production costs of the alloys (e.g., [17,24]).…”

Section: Introductionmentioning

confidence: 99%

“…as well as the mechanisms' subsequent effect on engineering properties. It has been reported that the addition of yttrium leads to (a) improved ductility and homogeneous deformation due to activation of <c+a> dislocations [11,20,21,42], (b) improved creep resistances due to forest dislocation hardening [18], (c) retardation of the kinetics associated with static recrystallization and grain coarsening, which suggest pinning of grain boundaries [14], (d) grain boundary rotation/sliding preventing the nucleation and propagation of cracks [19], and (e) improved corrosion resistance due to the formation of an enhanced oxide film [43,44].…”

Section: Introductionmentioning

confidence: 99%

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Atomic-scale investigation of creep behavior in nanocrystalline Mg and Mg–Y alloys

2015

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Magnesium (Mg) and its alloys offer great potential for reducing vehicular mass and energy consumption due to their inherently low densities. Historically, widespread applicability has been limited by low strength properties compared to other structural Al-, Ti-and Fe-based alloys. However, recent studies have demonstrated high-specific-strength in a number of nanocrystalline Mg-alloys. Even so, applications of these alloys would be restricted to low-temperature automotive components due to microstructural instability under high temperature creep loading. Hence, this work aims to gain a better understanding of creep and associated deformation behavior of columnar nanocrystalline Mg and Mg-yttrium (Y) (up to 3at.%Y(10wt.%Y)) with a grain size of 5 nm and 10 nm. Using molecular dynamics (MD) simulations, nanocrystalline magnesium with and without local concentrations of yttrium is subjected to constant-stress loading ranging from 0 to 500 MPa at different initial temperatures ranging from 473 to 723 K. In pure Mg, the analyses of the diffusion coefficient and energy barrier reveal that at lower temperatures (i.e., T < ~423K) the contribution of grain boundary diffusion to the overall creep deformation is stronger that the contribution of lattice diffusion. However, at higher temperatures (T > ~423K) lattice diffusion dominates the overall creep behavior. Interestingly, for the first time, we have shown that the(101 ̅ 1), (101 ̅ 2),(101 ̅ 3) and (101 ̅ 6) boundary sliding energy is reduced with the addition of yttrium. This softening effect in the presence of yttrium suggests that the experimentally observed high temperature beneficial effects of yttrium addition is likely to be attributed to some combination of other reported creep strengthening mechanisms or phenomena such as formation of stable yttrium oxides at grain boundaries or increased forest dislocation-based hardening.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: E Effect Of Yttrium On the Grain Boundary Slidingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Atomic-scale investigation of creep behavior in nanocrystalline Mg and Mg–Y alloys

2015

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Tensile Deformation Behaviors in a Fine‐Grained, Rolled Mg–3Al–3Sn Alloy at Room Temperature up to 250 °C

et al. 2014

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Uniaxial tensile tests were performed on fine‐grained, rolled AT33 alloy at strain rates of 1.0 × 10−4–1.0 × 10−1 s−1 and temperatures of 25–250 °C. The rolled AT33 alloy with an average grain size of 7 μm was produced by cast‐rolling and hot‐rolling. The relative deformation mechanisms at high temperature were investigated in this study. It was found that the strain rate sensitivity increases from 0.01 at room temperature to 0.13 at 250 °C. The average stress exponent and the activation energy have been calculated to be 6.5 and 145 kJ mol−1, respectively, indicating that the dominant tensile deformation mechanism is dislocation climb‐controlled creep profiting from the lattice self‐diffusion. The dispersed nano‐sized Mg2Sn particles in the rolled AT33 alloy increase dislocation accumulation, which not only contributes to a promising tensile strength at high temperature but also provides a high driving force for the dynamic recrystallization (DRX). It has found that DRX is mainly responsible for the obtained high tensile ductility of 76–205% at temperatures of 200–250 °C.

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An Unusual Extrusion Texture in Mg–Gd–Y–Zr Alloys

et al. 2016

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Texture evolution is studied by EBSD in Mg–9Gd–4Y–0.4Zr (GW94), Mg–5Gd–4Y–0.4Zr (GW54), and Mg–5Gd–0.4Zr (GW50) alloys after processing with two extrusion‐ratios of 19:1 and 8:1. While the alloys show common extrusion textures at the low extrusion‐ratio of 8:1, an unusual extrusion texture is observed in the GW94 alloy at the high extrusion‐ratio of 19:1 with the (0001) basal planes aligned perpendicular to the extrusion axis. This unusual texture decreases at lower extrusion‐ratios and/or lower alloy contents. It is proposed that rare‐earth (RE) elements modify the texture by retarding recrystallization in solute drag effects on grain boundaries and pinning effects of RE‐rich precipitates.

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The relation between ductility and stacking fault energies in Mg and Mg–Y alloys

Cited by 494 publications

References 50 publications

Atomic-scale investigation of creep behavior in nanocrystalline Mg and Mg–Y alloys

Atomic-scale investigation of creep behavior in nanocrystalline Mg and Mg–Y alloys

Tensile Deformation Behaviors in a Fine‐Grained, Rolled Mg–3Al–3Sn Alloy at Room Temperature up to 250 °C

An Unusual Extrusion Texture in Mg–Gd–Y–Zr Alloys

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