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Journal ArticleDOI: 10.1016/J.JALLCOM.2020.158201

Deformation behavior of Mg–5Y–2Nd–0.5Zr alloys with different Sm additions

05 Mar 2021-Journal of Alloys and Compounds (Elsevier BV)-Vol. 856, pp 158201
Abstract: Herein, we studied the microstructural evolution and deformation behavior of aged Mg–5Y–2Nd–xSm–0.5Zr (x = 1, 3, and 5 wt%) alloys during uniaxial compression at room temperature by transmission electron microscopy and quasi-in-situ electron backscatter diffraction techniques. The microstructures of Mg–5Y–2Nd–xSm–0.5Zr alloys are refined by the addition of Sm, with more occurrences of Mg(Nd, Sm) precipitates. The average grain size decreased significantly with increasing Sm content, from 80.4 µm (1 wt% Sm) to 64.8 µm (3 wt% Sm) and 50.0 µm (5 wt% Sm). The Mg–5Y–2Nd–3Sm–0.5Zr alloy exhibited a maximum compressive strength of 390.1 MPa and a maximum strain (e) of 0.103 at room temperature; {10−12} tensile twinning and dislocation slips are the main plastic deformation modes of Mg–5Y–2Nd–xSm–0.5Zr alloys during compression at room temperature. A number of and dislocations were observed in the aged Mg–5Y–2Nd–3Sm–0.5Zr alloy. The optimized ductility value is attributable to grain refinement; elemental Sm promotes the activation of the non-basal slip dislocations and interactions between twins and dislocations. The strengthening mechanism mainly includes solid solution, fine-grain, and precipitation strengthening.

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11 results found


Journal ArticleDOI: 10.1016/J.JMST.2021.02.036
Yunwei Gui1, Yunwei Gui2, Lingxiao Ouyang2, Yibei Xue3  +1 moreInstitutions (3)
Abstract: Microstructure evolution and dynamic restoration mechanism of solution-treated Mg-4Y-2Nd-1Sm-0.5Zr alloy have been studied under three TMP parameters consisting of deformation temperatures (350–500 °C), strain rates (0.01–5 s−1), and strains (0.2, 0.4, and 0.8). A strong dynamic softening is observed in all stress-strain curves, even at higher strain rates (1 and 5 s−1) due to an adiabatic heating effect. Various stress-strain curves are applied to construct a processing map and develop an Arrhenius-type constitutive equation. With the prediction of the processing map, an optimal processing domain has been determined to be the temperature range 450–500 °C and strain rate range 0.01–0.1 s−1 at a strain of 0.8. The volume fraction of DRX grains is the largest in the corresponding domain of high temperature and low strain rate. For the effect of TMP parameters on the dynamic restoration, the discontinuous dynamic recrystallization (DDRX) and continuous DRX (CDRX) synergistic effect occur throughout the whole process at high temperature and high strain rate. In terms of high temperature and low strain rate, DDRX characteristics at a low strain and then the DDRX + CDRX synergistic effect is observed at a higher strain. Although the DRX process is weak at low temperature and low strain rate, deformation twins have occurred and provided nucleation sites for DRX grains.

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Topics: Strain rate (62%), Dynamic recrystallization (57%), Deformation (engineering) (55%) ... show more

4 Citations


Journal ArticleDOI: 10.1016/J.MATLET.2021.129824
Quanan Li1, Lipeng Yan1, Limin Zhu1, Xiaoya Chen1Institutions (1)
15 Jul 2021-Materials Letters
Abstract: The β′ phase rapid transformation of peak-aging hot extruded GW84 alloy after short secondary aging at 250 °C and 300 °C were studied in this paper. The results show that strengthening phase, β′ phase (Mg7(Gd,Y,Sm)) changed obviously, which is not recognised in previous studies. The strengthening phase is metastable β′ at first aging 200 °C × 96 h. After secondary aging at 250 °C for 7 min, some β′ precipitates transform into nano β (Mg5(Gd,Y,Sm)) particles, which exist at grain boundary, but there are still some β′ precipitates remaining at grain boundary. After secondary aging for 300 °C × 7 min, β′ precipitates completely transform into β particles, which grow up to sub-micron particles at grain boundary.

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Topics: Grain boundary (53%), Phase (matter) (51%)

2 Citations


Journal ArticleDOI: 10.1016/J.MTCOMM.2021.102282
Yunwei Gui1, Quanan Li1, Kaige Zhu2, Yibei Xue3Institutions (3)
Abstract: The room-temperature ductility of the Mg alloys is closely related to the deformation behavior of the twin. However, there are currently no effective criteria that can accurately predict in which grains twins will nucleate during plastic deformation. With the rapid development of artificial intelligence technology, the applications of machine learning in the microstructure design and predictions have become the highlight. In the present study, a novel Mg-4Y-3Nd-2Sm-0.5 Zr alloy is prepared so as to explore the twin nucleation behavior of Mg alloys by combining machine learning along with electron backscattered diffraction (EBSD) techniques. At a true strain of 0.05, twins are found in 68 grains of the 297 grains which are counted from the initial microstructure. Eight features that may affect the twin nucleation are selected, including the grain diameter, the number of neighboring grains, the Schmid factor, and so on. Furthermore, the relevant importance of eight features on twin nuclei are also sorted; the grain diameter of original grains and the Schmid factor of the tensile twins have the greatest influence on the twin nucleation. Three machine learning algorithms including XGBoost, ANN, and the proposed relevance based ensemble scheme are used to model the prediction of the twin nucleation. The proposed relevance based ensemble scheme achieved an AUC score of 0.880, which is higher than that of the ANN (0.879) and XGBoost (0.756). A better ROC and PR curve also validate the feasibility of the proposed scheme.

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Topics: Nucleation (54%)

2 Citations


Open accessJournal ArticleDOI: 10.1016/J.JMRT.2021.08.013
Qian Zhang1, Quanan Li1, Xiaoya Chen1, Jiaxin Zhao1  +2 moreInstitutions (1)
Abstract: Hot compression tests of Mg-Gd-Y-Zr alloy at different deformation temperatures and strains were carried out with Gleeble-1500 simulator at strain rate of 0.002 s−1. The microstructure evolution of 400 °C/0.002 s−1 sample under different strain was analyzed emphatically by transmission electron microscopy and electron backscatter diffraction technology. Dynamic precipitation characteristics and nucleation-expansion mechanism of dynamic recrystallization (DRX) were discussed in detail. The results indicated that the dynamic precipitation takes place prior to DRX, and the morphology, size and distribution of precipitates change with increasing strain. At the later stage of deformation, the large-size hard phase β-Mg5(Gd,Y) can induce the particle-stimulated nucleation (PSN) mechanism under large strain and act as an effective nucleation site for DRX. In addition, we constructed a schematic diagram of the DRX nucleation-expansion mechanism of Mg-Gd-Y-Zr alloy under high temperature deformation. The first layer of DRX grains is formed by discontinuous dynamic recrystallization (DDRX) mechanism characterized by grain boundary bulge out, and the precipitates distributed at the original grain boundary promote DDRX nucleation; The expansion of necklace structure depends on continuous dynamic recrystallization (CDRX) mechanism; Subgrain division can further refine DRX grains.

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Topics: Dynamic recrystallization (67%), Recrystallization (metallurgy) (60%), Nucleation (54%) ... show more

2 Citations


Journal ArticleDOI: 10.1016/J.MSEA.2021.142026
Qian Zhang1, Quan-an Li1, Xiaoya Chen1, Jian Bao1  +1 moreInstitutions (1)
Abstract: We have studied the microstructure evolution and deformation behavior of Mg-5Gd-3Y-(1Sn)-0.5Zr alloys during hot compression (T = 350 °C, 400 °C, 450 °C and 500 °C, e ˙ = 0.002 s−1, 0.01 s−1, 0.1 s−1 and 1 s−1) by transmission electron microscopy and electron backscattering technology. Sn can promote dynamic precipitation to activate the particle-stimulated nucleation (PSN) mechanism induced by the cluster precipitates and promote and dynamic recrystallization (DRX); in addition, Sn can inhibit the formation of high-angle grain boundaries (HAGBs) by reducing the activation of pyramidal and slip and delaying DRX. The two processes are in a competitive relationship with each other in the hot deformation of Mg-Gd-Y-Sn-Zr alloys. At low temperatures (350 °C–400 °C) and high strain rates, the former dominates: DRX is promoted, accompanied by a decrease in flow stress. At high temperatures (450 °C–500 °C) and low strain rates, the latter is dominant due to the absence of dynamic precipitation: DRX is delayed, and flow stress is increased accordingly. Flow stress between the two extreme deformation conditions is determined by the competitive relationship between them. We also found that the addition of Sn could increase the thermal deformation activation energy of Mg-Gd-Y-Zr alloys, weaken the texture and inhibit twin growth. Finally, we constructed a schematic diagram of the DRX mechanism during the thermal deformation process to illustrate the effects of PSN, CDRX, and DDRX on the evolution of the microstructure in detail.

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Topics: Dynamic recrystallization (56%), Flow stress (55%), Deformation (engineering) (53%) ... show more

2 Citations


References
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60 results found


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Topics: Software design (51%), Software (50%)

30,888 Citations


Journal ArticleDOI: 10.1007/BF02648537
M. H. Yoo1Institutions (1)
Abstract: The role of deformation twinning in fracture of hexagonal close-packed metals is reviewed from a theoretical point of view. Strength and ductility are correlated with the intrinsic physical and metallurgical variables. The importance of c + a slip and of both “tension” and “compression” twins as independent modes for a generalized polycrystalline deformation is emphasized. Effects of slip-twin and twin-twin interactions on crack initiation and high-order twinning are reviewed. The competitive role of twin nucleationvs crack initiation is discussed. Shortcomings of our current understanding of the role of twinning are indicated, and some futher studies are recommended.

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1,389 Citations


Journal ArticleDOI: 10.1016/S1359-6454(01)00297-X
Sean R. Agnew1, M. H. Yoo1, Carlos N. Tomé2Institutions (2)
03 Dec 2001-Acta Materialia
Abstract: The viscoplastic self-consistent model was used to interpret differences in the mechanical behavior of hexagonal close packed magnesium alloys. There are only subtle differences in the compression textures of magnesium and its solid solution alloys containing lithium or yttrium. However, the plane strain compression textures of the alloys showed an increasing tendency for the basal poles to rotate away from the “normal direction” towards the “rolling direction”. Texture simulations enabled these distinctions to be attributed to the increased activity of the non-basal 〈 c + a 〉 slip mode. The alloys had improved compressive ductilities compared to pure magnesium, and the increased c + a slip mode activity provides a satisfying explanation for this improvement, since it can accommodate c-axis compression within individual grains. Accounting for individual deformation mode hardening enabled the flow curves to be simulated and the anisotropic plastic response of textured wrought alloys to be mechanistically understood and predicted.

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Topics: Slip (materials science) (58%), Hardening (metallurgy) (50%), Solid solution (50%) ... show more

1,115 Citations


Journal ArticleDOI: 10.1016/0001-6160(55)90007-9
F.C Frank1, N ThompsonInstitutions (1)
01 Jan 1955-Acta Metallurgica
Abstract: In considerations of the crystallographic directions of loading needed to operate particular twinning systems, due attention is not always paid to the distinction between the strain due to complete twinning and the macroscopic strain due to formation of a thin twin lamella. The subdivision of the orientation diagram according to the twinning system which can be operated by axial loading is a more complicated one than customarily indicated. The hypothesis of a shear stress criterion for twinning leads to a further complexity of subdivision according to the sequence of preference of the various systems permitted within any one region.

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Topics: Crystal twinning (58%)

1,002 Citations


Open accessJournal ArticleDOI: 10.1016/J.ACTAMAT.2010.08.031
01 Jan 2011-Acta Materialia
Abstract: Mg–Y alloys show significantly enhanced room temperature ductility compared to pure Mg and other classical Mg wrought alloys. The presented study focuses on understanding the mechanisms for this ductility improvement by microstructure analysis, texture analysis and slip trace analysis based on electron backscatter diffraction and transmission electron microscopy. As expected, pure Mg mainly deforms by 〈a〉 basal slip and tensile twinning. In contrast, Mg–Y shows a high activity of compression twinning, secondary twinning and pyramidal 〈c + a〉 slip. These additional deformation modes cause a homogeneous deformation with a weaker basal texture, more balanced work hardening and enhanced ductility. Additionally, in Mg–Y shear bands are much more frequent and carry less strain than those in pure Mg. As a consequence, failure in shear bands occurs at significantly higher strain. The experimental results are discussed focusing on the mechanisms effecting the observed high activation of pyramidal deformation modes in Mg–Y.

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Topics: Slip (materials science) (56%), Work hardening (54%), Crystal twinning (54%) ... show more

536 Citations