Journal of Rare Earths最新文献_第4页

Synergistic improvement of damping capacity and mechanical properties of magnesium alloy prepared with UHP technology 超高压技术制备的镁合金阻尼能力和机械性能的协同改善

IF 5.2 1区化学 Q1 CHEMISTRY, APPLIED

Journal of Rare Earths

Pub Date : 2024-07-30 DOI: 10.1016/j.jre.2024.07.029

Dan Wang , Peizhao Huang , Ruizhi Wu , Hailiang Huang , Tao Zhong , Cunwei Zou , Yaqiang Song

The contradictory relationship between the damping capacity and strength of metals, governed by dislocation mechanisms, poses a challenge in improving simultaneously through dislocation strengthening. Accordingly, exploring novel methods to synergistically enhance mechanical properties and damping capacity is designated as a focal research subject in recent years. The study at hand aims to tackle this challenge through the manipulation of microstructures in Mg-Y-Er-Zn-Zr alloy via ultra-high pressure (UHP) heat treatment, yielding Mg-based alloys of exceptionally lightweight with outstanding damping and mechanical characteristics. After UHP, a significant refinement in the alloy's grain size is observed, with the average grain size decreasing from 114 to 23 μm, accompanied by substantial introduction of dislocations into the matrix, along with the emergence of twin within the matrix. The tensile strength of M-6GPa-1000 alloy subjected to UHP treatment achieves 326 MPa, demonstrating a 95% increase compared to ordinary heat treatment alloys while maintaining an elongation of 11.9%. Additionally, the damping capacity value Q⁻¹ of M-6GPa-1000 alloy treated with UHP during the low-strain zone is 0.03, exhibiting a threefold increase compared to that of the conventionally heat-treated alloy. Through UHP treatment, the alloy's microstructure is regulated, achieving a synergistic enhancement of strength and damping capacity. The study comprehensively analyzes the synergistic improvement of mechanical and damping characteristics in the alloy. The proposed UHP technology holds significant potential for the fabrication of advanced Mg-Re components.

金属的阻尼能力和强度之间的矛盾关系受位错机制的支配，这对通过位错强化同时提高阻尼能力提出了挑战。因此，探索协同增强机械性能和阻尼能力的新方法成为近年来的重点研究课题。本研究旨在通过超高压（UHP）热处理对 Mg-Y-Er-Zn-Zr 合金的微观结构进行处理，从而获得具有出色阻尼和机械特性的超轻镁基合金，以应对这一挑战。经过超高压热处理后，合金的晶粒尺寸明显细化，平均晶粒尺寸从 114 微米减小到 23 微米，同时在基体中引入了大量位错，并在基体中出现了孪晶。经过超高压处理的 M-6GPa-1000 合金的抗拉强度达到 326 兆帕，与普通热处理合金相比提高了 95%，同时伸长率保持在 11.9%。此外，经超高压处理的 M-6GPa-1000 合金在低应变区的阻尼能力值 Q-1 为 0.03，与普通热处理合金相比提高了三倍。通过超高压处理，合金的微观结构得到调节，实现了强度和阻尼能力的协同提高。本研究全面分析了合金机械性能和阻尼性能的协同改善。所提出的超高压技术为制造先进的镁铼合金部件提供了巨大的潜力。

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引用次数: 0

Microstructure evolution of extruded Mg-RE-Ag alloy during short-time heat treatment 挤压 Mg-RE-Ag 合金在短时间热处理过程中的微观结构演变

IF 5.2 1区化学 Q1 CHEMISTRY, APPLIED

Journal of Rare Earths

Pub Date : 2024-07-25 DOI: 10.1016/j.jre.2024.07.025

Zehua Li , Jinghuai Zhang , Shujuan Liu , Jiaming Hao , Liyuan Liu , Yuying He , Haodong Zhang , Xingkai Jiao , Xiaobo Zhang , Ruizhi Wu

Microstructure regulation via short-time heat treatment is conducive to the optimization in the microstructure and properties of precipitable magnesium (Mg) alloys, but there is currently a lack of relevant studies. In this work, the microstructure evolution of a Mg-RE-Ag alloy during different short-time heat treatments was characterized and discussed. The results show that extreme short-time heat treatment (ESHT, e.g., 2 min) at 450–480 °C can greatly increase solute concentration in Mg matrix through the rapid re-dissolution of the second-phase and simultaneously maintain fine grains, while the ESHT at a too high temperature (e.g., 510 °C) is not suitable due to excessive grain growth and coarse second phase regenerated at grain boundaries. It is found that 480 °C is the approximate critical temperature for appropriate ESHT, and further prolongation of the time will lead to excessive grain growth. It is suggested that in addition to grain boundary migration, grain rotation is activated, resulting in the annihilation of high-angle grain boundaries with relatively low misorientation, as well as the reduction in the ability of the residual second phase to pin grain boundaries. In addition, the reasons for the abnormal grain boundary segregation and grain boundary continuous phase were analyzed from the perspective of interfacial energy. This study provides a basis for effective microstructure regulation of Mg-RE alloys.

通过短时热处理调节微观结构有利于优化可沉淀镁（Mg）合金的微观结构和性能，但目前缺乏相关研究。本研究对 Mg-RE-Ag 合金在不同短时热处理过程中的微观结构演变进行了表征和讨论。结果表明，450-480 °C的极短时间热处理（ESHT，例如 2 分钟）可通过第二相的快速再溶解大大增加镁基体中的溶质浓度，同时保持细晶粒，而过高温度（例如 510 °C）的 ESHT 则不适合，因为会导致晶粒过度生长和晶界再生粗大的第二相。研究发现，480 ℃ 是适当 ESHT 的近似临界温度，进一步延长时间会导致晶粒过度生长。研究认为，除了晶界迁移之外，晶界旋转也会被激活，从而导致错向度相对较低的高角度晶界湮灭，并降低残余第二相针刺晶界的能力。此外，还从界面能的角度分析了异常晶界偏析和晶界连续相的原因。这项研究为有效调节 Mg-RE 合金的微观结构提供了依据。

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引用次数: 0

High strength and elongation of Mg-Gd-Nd-Zr alloy obtained by synergistic action of high-speed extrusion and short-time aging treatment 高速挤压和短时时效处理协同作用下获得的高强度和高延伸率镁-钆-钕-锆合金

IF 5.2 1区化学 Q1 CHEMISTRY, APPLIED

Journal of Rare Earths

Pub Date : 2024-07-11 DOI: 10.1016/j.jre.2024.07.008

Simin Shen , Guangxiao Ren , Xijuan Cao , Hongxia Wang , Binshan Wang , Jin Wang , Lifei Wang , Weili Cheng , Kwangseon Shin

Magnesium–gadolinium (Mg–Gd)-based alloys have excellent high-temperature properties and the addition of two heterogeneous rare earth (RE) elements may promote the formation of secondary phase for better-strengthened properties. Herein, novel Mg-7Gd-2Nd-0.5Zr (wt%) alloys were prepared by synergistic reaction induced by high-speed extrusion (EX) and short-time aging treatment (AT). The microstructures, textures, and mechanical properties of the resulting alloys were then comprehensively studied by various analytical methods. The result reveals that the as-cast Mg-7Gd-2Nd-0.5Zr (wt%) alloy is composed of α-Mg matrix and Mg₅(Gd,Nd) phase with bony and continuous networks at grain boundaries. The microstructure presents coarse deformed grains and fine recrystallized grains after high-speed EX, and formation of typical

(0001) ∥

ED extruded fiber texture and [

\bar{1} 2 \bar{1} 1

] RE texture is observed. The EX22 sample exhibits more Mg₅(Gd,Nd) precipitated phases, fuller DRXed grains, and shorter peak aging times than the EX9 sample. After the AT at 250 °C, the proportion of deformed grains decreases due to static recrystallization, which leads to a reduction in the average grain size and weakening of the texture intensity. Therefore, combined effect of all strengthening mechanisms aids in achieving balance of high-strength and high-elongation for Mg-7Gd-2Nd-0.5Zr (wt%) alloy. The values of yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of EX22-A sample at room temperature are found to be 292.5 MPa, 350.6 MPa, and 24.3%, respectively. Overall, this study provides relevant experimental basis and theoretical guidance for the development of high-strength Mg-RE alloys, which are useful for future consideration.

镁-钆（Mg-Gd）基合金具有优异的高温性能，添加两种异质稀土（RE）元素可促进次生相的形成，从而获得更好的强化性能。本文通过高速挤压（EX）和短时时效处理（AT）的协同反应制备了新型 Mg-7Gd-2Nd-0.5Zr (wt%) 合金。然后通过各种分析方法对所制备合金的微观结构、质地和力学性能进行了全面研究。结果表明，铸造时的 Mg-7Gd-2Nd-0.5Zr (wt%) 合金由 α-Mg 基体和 Mg5(Gd,Nd) 相组成，晶界处有骨状连续网络。高速挤压后，显微组织呈现粗大变形晶粒和细小再结晶晶粒，并形成典型的（0001）∥ED挤压纤维纹理和[1¯21¯1] RE纹理。与 EX9 样品相比，EX22 样品表现出更多的 Mg5（Gd,Nd）析出相、更饱满的 DRX 化晶粒和更短的峰值老化时间。在 250 °C AT 温度下，由于静态再结晶，变形晶粒的比例减少，导致平均晶粒尺寸减小，纹理强度减弱。因此，所有强化机制的综合作用有助于实现 Mg-7Gd-2Nd-0.5Zr (wt%) 合金的高强度和高延展性的平衡。室温下，EX22-A 样品的屈服强度（YS）、极限拉伸强度（UTS）和伸长率（EL）值分别为 292.5 兆帕、350.6 兆帕和 24.3%。总之，本研究为开发高强度 Mg-RE 合金提供了相关的实验依据和理论指导，值得今后借鉴。

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引用次数: 0

Interface structure of α-Mg/14H-LPSO: First-principles prediction and experimental study α-Mg/14H-LPSO 的界面结构：第一原理预测与实验研究

IF 5.2 1区化学 Q1 CHEMISTRY, APPLIED

Journal of Rare Earths

Pub Date : 2024-07-06 DOI: 10.1016/j.jre.2024.07.009

Yuan Shi, Xiaohua Zhang, Hongyan Yue, Chao Li

The interfacial structure of the α-Mg/14H-LPSO phase in rare earth-including magnesium alloy was investigated via high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging and first-principles calculations of density-functional theory. Eleven possible interfacial models were constructed according to the different terminations of the LPSO phase, and the corresponding interfacial energies were calculated, from which the four most stable structures (Ter1-MgY-hollow, Ter2-Zn-hollow, Ter3-MgYII-hollow and Ter4-Mg-bridge) were obtained. The interfacial phase diagrams related to the Y chemical potentials were obtained from the calculations, and the most stable interfacial structure was evaluated. Ter1-MgY-hollow and Ter2-Zn-hollow have the lowest interfacial energies in the range of −0.7 eV < Δμ_Y < −0.6 eV, where fluctuating change of state is the minimized and the interface is the most stable. The separation work of the two models was calculated to predict the bonding strength of the structures at both ends of the interface. The calculation results show that the maximum interfacial separation work is 1.45 J/m² for the interface model of α-Mg and 14H-LPSO phase structure with Ter2-Zn-hollow termination.

通过高角度环形暗场扫描透射电子显微镜（HAADF-STEM）成像和密度泛函理论的第一性原理计算，研究了包括稀土在内的镁合金中α-Mg/14H-LPSO相的界面结构。根据 LPSO 相的不同终止构建了十一种可能的界面模型，并计算了相应的界面能量，从中得到了四种最稳定的结构（Ter1-MgY-空心、Ter2-Zn-空心、Ter3-MgYII-空心和 Ter4-Mg-桥）。通过计算得到了与 Y 化学势相关的界面相图，并评估了最稳定的界面结构。在-0.7 eV < ΔμY < -0.6 eV范围内，Ter1-MgY-空心和Ter2-Zn-空心的界面能最低，其中状态的波动变化最小，界面最稳定。通过计算两种模型的分离功来预测界面两端结构的键合强度。计算结果表明，α-Mg 和 14H-LPSO 相结构与 Ter2-Zn 空心终止的界面模型的最大界面分离功为 1.45 J/m2。

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引用次数: 0

Mechanism of corrosion behavior induced by precipitates under plastic compressive stress in Mg-Gd-Y alloys 镁钆钇合金在塑性压应力作用下析出物诱发腐蚀行为的机理

IF 5.2 1区化学 Q1 CHEMISTRY, APPLIED

Journal of Rare Earths

Pub Date : 2024-07-02 DOI: 10.1016/j.jre.2024.06.041

Lele Liu, Ping Wang, Yimeng Wang, Weiming Li, Min Xu, Haoyan Xue

Through independently developed stress-loading equipment, stress corrosion tests on Mg-Gd-Y alloy were conducted in a 3.5 wt% NaCl solution. The effects of plastic compressive stress on the corrosion behavior of the alloy were thoroughly investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) among other microscopic analysis techniques. The results indicate that the alloy mainly consists of α-Mg grains, Mg₂₄Y₅ phase, Mg₅Gd phase, and LPSO phase. The corrosion behavior of the Mg-Gd-Y alloy is significantly influenced by the microstructure of the interface between the precipitates and the matrix, the potential difference, and the stress state. In the unstressed state, the Mg₂₄Y₅ phase first induces corrosion at the edges of the α-Mg grain boundaries, which then spreads internally. Upon the application of plastic stress, the corrosion-inducing capability of the LPSO phase on α-Mg grains notably increases. This discovery provides new insights into the mechanisms by which plastic compressive stress affects the corrosion behavior of Mg-Gd-Y alloys and offers an important basis for the theoretical research and anti-corrosion design in the engineering applications of this alloy.

通过自主研发的应力加载设备，在 3.5 wt% 的 NaCl 溶液中对 Mg-Gd-Y 合金进行了应力腐蚀试验。利用扫描电子显微镜（SEM）和透射电子显微镜（TEM）等显微分析技术深入研究了塑性压应力对合金腐蚀行为的影响。结果表明，合金主要由 α-镁晶粒、Mg24Y5 相、Mg5Gd 相和 LPSO 相组成。Mg-Gd-Y 合金的腐蚀行为受到析出物与基体之间界面的微观结构、电位差和应力状态的显著影响。在非应力状态下，Mg24Y5 相首先在 α-Mg 晶界边缘引起腐蚀，然后向内部扩散。当施加塑性应力时，LPSO 相对 α-Mg 晶粒的腐蚀诱导能力明显增强。这一发现为塑性压应力影响 Mg-Gd-Y 合金腐蚀行为的机制提供了新的见解，并为该合金在工程应用中的理论研究和防腐蚀设计提供了重要依据。

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引用次数: 0

Effect of heat-treatment on microstructure and deformation behavior of Mg-8.5Li-6.6Zn-1.5Y alloy 热处理对 Mg-8.5Li-6.6Zn-1.5Y 合金微观结构和变形行为的影响

IF 5.2 1区化学 Q1 CHEMISTRY, APPLIED

Journal of Rare Earths

Pub Date : 2024-06-29 DOI: 10.1016/j.jre.2024.06.039

Yu Wang , Penghao Wang , Jingpeng Xiong , Jian Wang , Yong Liu

The Mg-8.5Li-6.6Zn-1.5Y (wt%) as-cast alloy exhibits a (β+α) duplex phase structure. Interspersed eutectics, primarily reticular I-phase, predominantly form along phase and grain boundaries, enhancing the strength but leading to a reduction in ductility due to the brittle nature of the I-phase. This study focuses on modifying the alloy's microstructure through heat treatment to simultaneously improve both strength and ductility. Heating the alloy at 450 °C/6 h results in the dissolution of continuous reticular I-phase and the massive α-Mg. Subsequent slow cooling facilitates the reintroduction of α-Mg, with the cooling rate directly impacting the mean size of the α-Mg phase. The slower the cooling, the larger the α-Mg phase. The strength and ductility of LZW861 alloy are simultaneously enhanced by heat treatment, particularly in the air-cooled (450 °C/6 h-AC) alloy, while the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) increases from 147 MPa, 189 MPa, and 17.8% to 192 MPa, 242 MPa, and 22.3%, respectively, compared to the as-cast state. This increase in strength can be attributed partly to the precipitation of fine needle-like α-Mg uniformly dispersed in the β-Li matrix. Additionally, the increase in dispersed (Li,Mg)₃Zn nanoparticles contributes to matrix strengthening. The enhancement of ductility after 450 °C/6 h-AC heat treatment is ascribed to the dissolution of reticulated I-phase and the refinement of α-Mg phase, which enhance interphase deformation compatibility and weaken crack initiation at dispersed β/α interface.

镁-8.5锂-6.6锌-1.5铍（重量百分比）铸造合金呈现出（β+α）双相结构。穿插共晶（主要是网状 I 相）主要沿着相界和晶界形成，从而提高了强度，但由于 I 相的脆性，导致延展性降低。本研究的重点是通过热处理改变合金的微观结构，从而同时提高强度和延展性。在 450 °C/6 h 的温度下加热合金会导致连续网状 I 相和大量 α-Mg 的溶解。随后的缓慢冷却有利于重新引入α-镁，冷却速度直接影响α-镁相的平均尺寸。冷却速度越慢，α-镁相就越大。热处理同时提高了 LZW861 合金的强度和延展性，尤其是空冷（450 °C/6 h-AC）合金，与铸造状态相比，屈服强度（YS）、极限抗拉强度（UTS）和伸长率（EL）分别从 147 兆帕、189 兆帕和 17.8% 提高到 192 兆帕、242 兆帕和 22.3%。强度的提高部分归因于均匀分散在 β-Li 基体中的细针状 α-Mg 的析出。此外，分散的（Li,Mg）3Zn 纳米颗粒的增加也有助于基体的强化。450 °C/6 h-AC 热处理后延展性的增强归因于网状 I 相的溶解和 α-Mg 相的细化，它们增强了相间变形的相容性，并削弱了分散的 β/α 界面的裂纹萌生。

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引用次数: 0

High strength and high ductility Mg-Gd-Y-Zn-Zr alloys obtained by controlling texture and dynamic precipitation through LPSO phase structure of different initial morphologies 通过控制不同初始形态的 LPSO 相结构的质地和动态沉淀获得高强度和高延展性 Mg-Gd-Y-Zn-Zr 合金

IF 5.2 1区化学 Q1 CHEMISTRY, APPLIED

Journal of Rare Earths

Pub Date : 2024-06-29 DOI: 10.1016/j.jre.2024.06.042

Yayun He , Rui Guo , Xi Zhao , Zhimin Zhang

This paper investigated the effects of three different initial phase structures on the microstructure evolution and tensile properties of extruded Mg-Gd-Y-Zn-Zr alloy, using an extrusion ratio of 3.6. These three initial phase structures were obtained by heat treatment, which is narrow spacing long-period stacking ordered phase (LPSO) phase structure alloy (EN alloy), wide spacing LPSO phase structure alloy (EW alloy), and narrow spacing LPSO phase and β phase overlapping phase structure alloy (EO alloy). The dynamic recrystallization (DRX) and dynamic precipitation behavior of extruded alloys with different initial structures, as well as their strengthening and ductility mechanisms were studied in detail. After hot extrusion with a low extrusion ratio, the alloy exhibits a bimodal structure composed of undynamic recrystallization (UN-DRX) grains and dynamic recrystallization (DRX) grains with strong textures. The narrow-spacing LPSO phase structure inhibits DRX and dynamic precipitation, while both the wide-spacing LPSO phase structure and the overlapping phase structure alloys promote DRX and dynamic precipitation. The strength improvement is mainly due to the strong texture and internal dislocation pinning of the undynamic recrystallization zone (UN-DRX) and the high strengthening effect of the narrow spacing LPSO phase. Although the promotion of DRX improves grain boundary strengthening effect, it cannot make up for reducing the UN-DRXed grain strengthening effect. A lower volume fraction of β dynamic precipitation phase is beneficial for improving the ductility of the alloy.

本文研究了挤压比为 3.6 时三种不同初始相结构对挤压 Mg-Gd-Y-Zn-Zr 合金微观结构演变和拉伸性能的影响。这三种初始相结构是通过热处理获得的，分别是窄间距长周期堆积有序相（LPSO）相结构合金（EN合金）、宽间距LPSO相结构合金（EW合金）和窄间距LPSO相与β相重叠相结构合金（EO合金）。详细研究了不同初始结构挤压合金的动态再结晶（DRX）和动态析出行为及其强化和延展机制。在低挤压比热挤压后，合金呈现出由非动态再结晶（UN-DRX）晶粒和具有强纹理的动态再结晶（DRX）晶粒组成的双峰结构。窄间距 LPSO 相结构抑制了 DRX 和动态析出，而宽间距 LPSO 相结构和重叠相结构合金则促进了 DRX 和动态析出。强度的提高主要得益于非动态再结晶区（UN-DRX）的强质地和内部位错钉扎以及窄间距 LPSO 相的高强化效果。虽然 DRX 的促进提高了晶界强化效果，但无法弥补 UN-DRX 晶界强化效果的降低。降低β动态析出相的体积分数有利于提高合金的延展性。

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引用次数: 0

Mechanical property and anisotropy of as-extruded Mg–Zn–Y–Mn alloys with different volume fraction of long-period stacking ordered (LPSO) phase 具有不同长周期有序堆积相（LPSO）体积分数的挤压成型 Mg-Zn-Y-Mn 合金的力学性能和各向异性

IF 5.2 1区化学 Q1 CHEMISTRY, APPLIED

Journal of Rare Earths

Pub Date : 2024-06-29 DOI: 10.1016/j.jre.2024.06.034

Dahui Liang , Mincong Chen , Chuanqiang Li , Zhipei Tong , Yong Dong , Dong Bian

Effects of different volume fraction of long-period stacking ordered (LPSO) phase on the microstructure, mechanical property and anisotropy of the as-extruded Mg-xZn-yY-0.1Mn (x = 1 wt%, 2 wt%, 4 wt% and y = 2 wt%, 4 wt%, 8 wt%) alloys were studied by an optical microscope, a scanning electron microscope, texture analysis, a transmission electron microscope and tensile testing. The results reveal that the volume fraction of LPSO phase increases from ZW12 to ZW24 to ZW48 alloys with the elevating Zn and Y content but constant Y/Zn value, and the mechanical strength of the LPSO-containing Mg–Zn–Y–Mn system is gradually improved when increasing LPSO phases. With the highest volume fraction of LPSO phase, ZW48 alloy presents the highest ultimate tensile strength (UTS) of 427 MPa along the extrusion direction (ED) when compared with those of ZW12 alloy with the UTS of 307 MPa and ZW24 alloy with the UTS of 347 MPa. Moreover, the elongation ratio of ZW48 alloy is maintained to moderate 9.9%, which is also the highest among three studied alloys. On the other hand, texture analysis demonstrates that the basal texture of the α-Mg phase in the ZW48 alloy is significantly weakened by the generation of more LPSO phases. On the contrary, a high texture intensity of α-Mg phase and obvious mechanical anisotropy can be observed for the ZW12 alloy. However, mechanical anisotropy still exists in the ZW48 alloy containing massive LPSO phases, which is attributed primarily to the zonal distribution of large LPSO along the ED.

通过光学显微镜、扫描电子显微镜、纹理分析、透射电子显微镜和拉伸试验研究了不同体积分数的长周期堆积有序相（LPSO）对挤压成型的Mg-xZn-yY-0.1Mn（x=1 wt%、2 wt%、4 wt%，y=2 wt%、4 wt%、8 wt%）合金的显微组织、力学性能和各向异性的影响。结果表明，随着 Zn 和 Y 含量的增加，在 Y/Zn 值不变的情况下，LPSO 相的体积分数从 ZW12 到 ZW24 再到 ZW48，含 LPSO 的 Mg-Zn-Y-Mn 体系的机械强度随着 LPSO 相的增加而逐渐提高。在 LPSO 相体积分数最高的情况下，ZW48 合金沿挤压方向（ED）的极限拉伸强度（UTS）最高，达到 427 MPa，而 ZW12 合金的极限拉伸强度（UTS）为 307 MPa，ZW24 合金的极限拉伸强度（UTS）为 347 MPa。此外，ZW48 合金的伸长率保持在适中的 9.9%，也是所研究的三种合金中最高的。另一方面，纹理分析表明，ZW48 合金中 α-Mg 相的基底纹理因生成更多 LPSO 相而明显减弱。相反，ZW12 合金中的α-Mg 相具有较高的纹理强度和明显的力学各向异性。然而，在含有大量 LPSO 相的 ZW48 合金中，机械各向异性仍然存在，这主要归因于大型 LPSO 沿 ED 的带状分布。

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引用次数: 0

Intergranular deformation mechanism stimulated by {10-12} extension twins in AZ81-La alloy AZ81-La 合金中{10-12}延伸孪晶激发的晶间变形机制

IF 5.2 1区化学 Q1 CHEMISTRY, APPLIED

Journal of Rare Earths

Pub Date : 2024-06-27 DOI: 10.1016/j.jre.2024.06.033

Biwu Zhu , Jing Su , Xiao Liu , Changping Tang , Wenhui Liu , Luoxing Li , Congchang Xu , Pengcheng Guo

In polycrystalline Mg-RE magnesium alloys, the lattice parameter, dislocation dynamics and critical resolved shear stress (CRSS) for various deformation modes are altered with the addition of RE atom, finally affecting deformation mode and strain accommodation mechanism among neighboring grains. Uniaxial compression tests were performed on as-extruded AZ81-La Mg alloy samples with the c-axis of the majority of crystals vertical to the compression direction. Twin variants and dominant slip systems were examined by electron backscattered diffraction (EBSD) technique. It is found by in-grain misoriention axis (IGMA) analysis that the plastic deformation is mainly accommodated by a combination of the pyramidal <c+a> slip and the basal <a> slip. The dominant twin variant is

{0 \bar{1} 12}

<

01 \bar{1} 1

> and

{1 \bar{1} 02}

<

\bar{1} 101

>. Here, we applied a modified displacement gradient accommodation (m-DGA) method to evaluate the selection mechanism of twin/slip in neighbour grain stimulated by

{10 \bar{1} 2}

extension twin. It is found that the activated slip system and/or twin variant in the neighbouring grain is determined by the accommodation of the major shear strain induced by

{10 \bar{1} 2}

extension twin in such a way that strain concentration along grain boundaries can be relaxed.

在多晶 Mg-RE 镁合金中，RE 原子的加入会改变晶格参数、位错动力学和各种变形模式的临界分辨剪切应力（CRSS），并最终影响相邻晶粒间的变形模式和应变容纳机制。在大多数晶体的 c 轴垂直于压缩方向的 AZ81-La 镁合金样品上进行了单轴压缩试验。通过电子反向散射衍射（EBSD）技术检测了孪晶变体和主要滑移系统。通过晶粒内失向轴（IGMA）分析发现，塑性变形主要是由金字塔形滑移和基底滑移组合而成。主要的孪生变体是{01¯12} <011¯1>和{11¯02} <1¯101>。在此，我们应用改进的位移梯度容纳（m-DGA）方法来评估{101¯2}延伸孪晶刺激邻近晶粒孪晶/滑移的选择机制。结果发现，{101¯2}延伸孪晶诱发的主要剪切应变的容纳方式决定了邻近晶粒中的激活滑移系统和/或孪晶变体，从而可以放松沿晶界的应变集中。

{"title":"Intergranular deformation mechanism stimulated by {10-12} extension twins in AZ81-La alloy","authors":"Biwu Zhu , Jing Su , Xiao Liu , Changping Tang , Wenhui Liu , Luoxing Li , Congchang Xu , Pengcheng Guo","doi":"10.1016/j.jre.2024.06.033","DOIUrl":"10.1016/j.jre.2024.06.033","url":null,"abstract":"<div><div>In polycrystalline Mg-RE magnesium alloys, the lattice parameter, dislocation dynamics and critical resolved shear stress (CRSS) for various deformation modes are altered with the addition of RE atom, finally affecting deformation mode and strain accommodation mechanism among neighboring grains. Uniaxial compression tests were performed on as-extruded AZ81-La Mg alloy samples with the <em>c</em>-axis of the majority of crystals vertical to the compression direction. Twin variants and dominant slip systems were examined by electron backscattered diffraction (EBSD) technique. It is found by in-grain misoriention axis (IGMA) analysis that the plastic deformation is mainly accommodated by a combination of the pyramidal <<em>c</em>+<em>a</em>> slip and the basal <<em>a</em>> slip. The dominant twin variant is <span><math><mrow><mrow><mo>{</mo><mn>0</mn></mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>12</mn><mo>}</mo></mrow></mrow></math></span> <<span><math><mrow><mn>01</mn><mover><mn>1</mn><mo>¯</mo></mover><mn>1</mn></mrow></math></span>> and <span><math><mrow><mrow><mo>{</mo><mn>1</mn></mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>02</mn><mo>}</mo></mrow></mrow></math></span> <<span><math><mrow><mover><mn>1</mn><mo>¯</mo></mover><mn>101</mn></mrow></math></span>>. Here, we applied a modified displacement gradient accommodation (m-DGA) method to evaluate the selection mechanism of twin/slip in neighbour grain stimulated by <span><math><mrow><mrow><mo>{</mo><mn>10</mn></mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>2</mn><mo>}</mo></mrow></mrow></math></span> extension twin. It is found that the activated slip system and/or twin variant in the neighbouring grain is determined by the accommodation of the major shear strain induced by <span><math><mrow><mrow><mo>{</mo><mn>10</mn></mrow><mover><mn>1</mn><mo>¯</mo></mover><mrow><mn>2</mn><mo>}</mo></mrow></mrow></math></span> extension twin in such a way that strain concentration along grain boundaries can be relaxed.</div></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"42 12","pages":"Pages 2325-2331"},"PeriodicalIF":5.2,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142719710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Recovery of rare earth elements from rare earth molten salt electrolytic slag via fluorine fixation by MgCl2 roasting 通过氯化镁焙烧氟固定从稀土熔盐电解渣中回收稀土元素

IF 5.2 1区化学 Q1 CHEMISTRY, APPLIED

Journal of Rare Earths

Pub Date : 2024-06-07 DOI: 10.1016/j.jre.2024.06.010

Rare earth fluoride molten-salt electrolytic slag (REFES) is a precious rare earth element (REE) secondary resource, and considerable amounts of REEs exist in REFES as REF₃; they are difficult to dissolve in acid or water and impede efficient REE extraction. In REFES recovery, the REF₃ species in REFES are usually transformed into acid-soluble rare earth compounds by NaOH roasting or sulfating roasting and then extracted by acid leaching. Moreover, the fluorides in REFES are released as HF gas in the roasting process or enter the liquid phase during the water washing process; both of these processes cause fluorine pollution. Fixing the fluorine into the solid slag provides a way to avoid fluorine pollution. In this study, a novel method was proposed to extract REEs from REFES via MgCl₂ roasting followed by HCl leaching. Thermodynamics calculations and thermogravimetry‒differential thermal analyses (TG-DTA) were conducted to investigate the reactions occurring in the roasting process. First, MgCl₂ reacts with the REF₃ and RE₂O₃ to form RECl₃ and REOCl, respectively. Second, the RECl₃ absorbs water and forms RE(OH)₃. Third, MgCl₂·6H₂O is gradually dehydrated to MgCl₂·2H₂O and reacts with REF₃ and RE(OH)₃, and REOCl, MgF₂ and MgO are formed. Through HCl leaching, the REOCl in the roasting products is leached by HCl acid, while fluoride remains in the solid slag as MgF₂. The optimum experimental conditions are as follows: mass ratio of MgCl₂ to REFES of 30%, roasting temperature of 700 °C, roasting time of 2 h, hydrochloride acid concentration of 4 mol/L, leaching time of 2 h, leaching temperature of 90 °C and leaching L/S ratio of 20:1. The efficiencies for total leaching of the REEs, La, Ce, Pr, and Nd are 99.13%, 99.20%, 98.42%, 99.38%, and 99.08%, respectively. Moreover, the concentration of fluoride in the leaching solution is 2.191 × 10⁻⁶ mol/L. This method has a short process flow with low reagent costs, and the problem of fluoride pollution from REFES recovery is solved; thus, our study has great industrial application potential.

稀土氟化物熔盐电解渣（REFES）是一种珍贵的稀土元素（REE）二次资源，在 REFES 中以 REF3 的形式存在大量稀土元素，它们难以溶解于酸或水中，阻碍了稀土元素的有效提取。在 REFES 回收中，REFES 中的 REF3 通常通过 NaOH 焙烧或硫酸化焙烧转化为酸溶性稀土化合物，然后通过酸浸出法提取。此外，REFES 中的氟化物在焙烧过程中以 HF 气体形式释放，或在水洗过程中进入液相，这两个过程都会造成氟污染。将氟固定在固体炉渣中是避免氟污染的一种方法。本研究提出了一种新方法，通过氯化镁焙烧后再进行盐酸浸出，从 REFES 中提取 REEs。为研究焙烧过程中发生的反应，进行了热力学计算和热重-差热分析（TG-DTA）。首先，氯化镁与 REF3 和 RE2O3 反应，分别生成 RECl3 和 REOCl。第二，RECl3 吸水后生成 RE(OH)3。第三，MgCl2-6H2O 逐渐脱水为 MgCl2-2H2O，并与 REF3 和 RE(OH)3 反应，生成 REOCl、MgF2 和 MgO。通过盐酸浸出，焙烧产物中的 REOCl 被盐酸浸出，而氟化物则以 MgF2 的形式留在固渣中。最佳实验条件如下：氯化镁与 REFES 的质量比为 30%，焙烧温度为 700 °C，焙烧时间为 2 小时，盐酸浓度为 4 mol/L，浸出时间为 2 小时，浸出温度为 90 °C，浸出 L/S 比为 20:1。REEs、La、Ce、Pr 和 Nd 的总浸出效率分别为 99.13%、99.20%、98.42%、99.38% 和 99.08%。此外，浸出液中氟化物的浓度为 2.191 × 10-6 mol/L。该方法工艺流程短，试剂成本低，解决了 REFES 回收过程中的氟污染问题，具有很大的工业应用潜力。

{"title":"Recovery of rare earth elements from rare earth molten salt electrolytic slag via fluorine fixation by MgCl2 roasting","authors":"","doi":"10.1016/j.jre.2024.06.010","DOIUrl":"10.1016/j.jre.2024.06.010","url":null,"abstract":"<div><div>Rare earth fluoride molten-salt electrolytic slag (REFES) is a precious rare earth element (REE) secondary resource, and considerable amounts of REEs exist in REFES as REF<sub>3</sub>; they are difficult to dissolve in acid or water and impede efficient REE extraction. In REFES recovery, the REF<sub>3</sub> species in REFES are usually transformed into acid-soluble rare earth compounds by NaOH roasting or sulfating roasting and then extracted by acid leaching. Moreover, the fluorides in REFES are released as HF gas in the roasting process or enter the liquid phase during the water washing process; both of these processes cause fluorine pollution. Fixing the fluorine into the solid slag provides a way to avoid fluorine pollution. In this study, a novel method was proposed to extract REEs from REFES via MgCl<sub>2</sub> roasting followed by HCl leaching. Thermodynamics calculations and thermogravimetry‒differential thermal analyses (TG-DTA) were conducted to investigate the reactions occurring in the roasting process. First, MgCl<sub>2</sub> reacts with the REF<sub>3</sub> and RE<sub>2</sub>O<sub>3</sub> to form RECl<sub>3</sub> and REOCl, respectively. Second, the RECl<sub>3</sub> absorbs water and forms RE(OH)<sub>3</sub>. Third, MgCl<sub>2</sub>·6H<sub>2</sub>O is gradually dehydrated to MgCl<sub>2</sub>·2H<sub>2</sub>O and reacts with REF<sub>3</sub> and RE(OH)<sub>3</sub>, and REOCl, MgF<sub>2</sub> and MgO are formed. Through HCl leaching, the REOCl in the roasting products is leached by HCl acid, while fluoride remains in the solid slag as MgF<sub>2</sub>. The optimum experimental conditions are as follows: mass ratio of MgCl<sub>2</sub> to REFES of 30%, roasting temperature of 700 °C, roasting time of 2 h, hydrochloride acid concentration of 4 mol/L, leaching time of 2 h, leaching temperature of 90 °C and leaching L/S ratio of 20:1. The efficiencies for total leaching of the REEs, La, Ce, Pr, and Nd are 99.13%, 99.20%, 98.42%, 99.38%, and 99.08%, respectively. Moreover, the concentration of fluoride in the leaching solution is 2.191 × 10<sup>−6</sup> mol/L. This method has a short process flow with low reagent costs, and the problem of fluoride pollution from REFES recovery is solved; thus, our study has great industrial application potential.</div></div>","PeriodicalId":16940,"journal":{"name":"Journal of Rare Earths","volume":"42 10","pages":"Pages 1979-1987"},"PeriodicalIF":5.2,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141402494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0