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学者姓名：王立华
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Abstract ：
弯曲变形是金属纳米材料最常见的变形方式之一。揭示金属纳米材料弯曲状态下的变形机制，建立微观结构、变形机制与力学性质之间的关联性，可为材料设计提供重要的理论依据。本文综述了面心立方(FCC)单晶金属纳米线在弯曲变形下力学性质与变形机制研究的主要进展：介绍了尺寸效应对弯曲应变下的材料力学性能的影响，概述了弯曲应变的大小对变形机制的影响；总结了金属纳米线中孪晶厚度对位错滑移，相变等塑性变形机制的影响；对比了金属纳米线弯曲与拉伸，压缩中变形机制的异同。最后对金属纳米线弯曲塑性变形机制研究所面临的难题以及有望解决该难题的原位实验技术的发展进行了展望。
Keyword ：
变形机制 变形机制 孪晶结构 孪晶结构 原子分辨率 原子分辨率 金属纳米线 金属纳米线 弯曲 弯曲
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| GB/T 7714 | 赵玉峰 , 李雪峤 , 王立华 et al. 面心立方结构金属纳米线弯曲变形机制研究进展 [J]. | 电子显微学报 , 2023 , 42 (02) : 238-251 . |
| MLA | 赵玉峰 et al. "面心立方结构金属纳米线弯曲变形机制研究进展" . | 电子显微学报 42 . 02 (2023) : 238-251 . |
| APA | 赵玉峰 , 李雪峤 , 王立华 , 韩晓东 . 面心立方结构金属纳米线弯曲变形机制研究进展 . | 电子显微学报 , 2023 , 42 (02) , 238-251 . |
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Abstract ：
The deformation of a single-crystal Fe48Mn32Co10Cr10 alloy is captured in situ at the atomic scale. The results show that full and partial dislocations, along with deformation twins, are involved in the deformation process. Partial dislocation activities result in the formation of nanotwins, high-density coherent twin boundaries, and incoherent twin boundaries. Full dislocations interact with the coherent/incoherent twin boundaries, and partial dislocations, thereby producing high strength and remarkable strain hardening. The observed high activity of full dislocations can be attributed to the inhomogeneous distribution of solid solution atoms in the alloy.{GRAPHICAL ABSTRACT}
Keyword ：
in-situ in-situ deformation twin deformation twin dislocation dislocation High-entropy alloys High-entropy alloys
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| GB/T 7714 | Ma, Yan , Qiu, Keliang , Xu, Ning et al. In-situ atomic-scale observation of dislocation and deformation twin interaction in FeMnCoCr high-entropy alloy [J]. | MATERIALS RESEARCH LETTERS , 2023 , 11 (12) : 1040-1047 . |
| MLA | Ma, Yan et al. "In-situ atomic-scale observation of dislocation and deformation twin interaction in FeMnCoCr high-entropy alloy" . | MATERIALS RESEARCH LETTERS 11 . 12 (2023) : 1040-1047 . |
| APA | Ma, Yan , Qiu, Keliang , Xu, Ning , Yang, Chengpeng , Zhang, Jiabao , Zhang, Zihao et al. In-situ atomic-scale observation of dislocation and deformation twin interaction in FeMnCoCr high-entropy alloy . | MATERIALS RESEARCH LETTERS , 2023 , 11 (12) , 1040-1047 . |
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| GB/T 7714 | Wang, Zhanxin , Guo, Yizhong , Ma, Yan et al. Effects of twin thicknesses on incoherent twin-boundary structures in face-centered cubic metals [J]. | SCIENCE CHINA-MATERIALS , 2023 , 66 (11) : 4342-4348 . |
| MLA | Wang, Zhanxin et al. "Effects of twin thicknesses on incoherent twin-boundary structures in face-centered cubic metals" . | SCIENCE CHINA-MATERIALS 66 . 11 (2023) : 4342-4348 . |
| APA | Wang, Zhanxin , Guo, Yizhong , Ma, Yan , Yang, Chengpeng , Zhai, Yadi , Yan, Xin et al. Effects of twin thicknesses on incoherent twin-boundary structures in face-centered cubic metals . | SCIENCE CHINA-MATERIALS , 2023 , 66 (11) , 4342-4348 . |
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Abstract ：
Permanent structural changes in pure metals that are caused by plastic activity are normally irreparable after unloading. Because of the lack of experimental evidence, it is unclear whether the plastic activity can be repaired as the size of the pure metals decreases to several nanometers; it is also unclear how the metals accommodate the plastic deformation. In this study, the in situ atomic-scale loading and unloading of similar to 2 nm Ag nanocrystals was investigated, and three modes of plastic deformation were observed: (i) the phase transition from the face-centered cubic (fcc) phase to the hexagonal close-packed (hcp) phase, (ii) stacking faults, and (iii) deformation twin nucleation. We show that all three modes resulted in structural changes that were reparable, and their generation and restoration during loading and unloading were observed in situ. We discovered that the deformation modes of nanosized metals can be predicted from the ratio of the energy barriers of the fcc-hcp phase transition (Delta gamma(H)) and the deformation twin nucleation (Delta gamma(T)), which differ from those of the theoretical modes of relatively large-sized metals. The proposed Delta gamma(H)/Delta gamma(T) criterion provides insights into the deformation mechanism of nanometals.
Keyword ：
atomic-scale atomic-scale phasetransition phasetransition stacking faults stacking faults in situ in situ reparable deformation reparable deformation deformationtwin deformationtwin
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| GB/T 7714 | Li, Dongwei , Wang, Zhanxin , Zhao, Yufeng et al. In Situ Atomic-Scale Quantitative Evidence of Plastic Activities Resulting in Reparable Deformation in Ultrasmall-Sized Ag Nanocrystals [J]. | ACS NANO , 2023 , 17 (23) : 23488-23497 . |
| MLA | Li, Dongwei et al. "In Situ Atomic-Scale Quantitative Evidence of Plastic Activities Resulting in Reparable Deformation in Ultrasmall-Sized Ag Nanocrystals" . | ACS NANO 17 . 23 (2023) : 23488-23497 . |
| APA | Li, Dongwei , Wang, Zhanxin , Zhao, Yufeng , Zeng, Weijing , Zhang, Zihao , Li, Shuai et al. In Situ Atomic-Scale Quantitative Evidence of Plastic Activities Resulting in Reparable Deformation in Ultrasmall-Sized Ag Nanocrystals . | ACS NANO , 2023 , 17 (23) , 23488-23497 . |
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Abstract ：
Understanding the plastic behavior of crack tips is crucial for improving the fracture toughness of nanometals. Although many studies are carried out, most previous studies focus on pure metals, and how the crack tip accommodates the plastic deformation of highly concentrated solid-solution alloys is unclear owing to a lack of direct atomic-scale evidence. In this study, the atomic-scale plastic behavior of the crack tip in face-centered cubic (FCC) AuCu alloy nanocrystals is observed in situ, which provides direct evidence that plastic deformation is governed by the generation of deformation twins and hexagonal close-packed (HCP) 2H and 4H phases, recurrence of reversible FCC-HCP phase transitions, and detwinning, which are rarely observed in pure metals. This unusual behavior originates from the inherent chemical inhomogeneity of the AuCu alloy, which inhibits twin thickening via partial dislocations on the adjacent plane, instead of random generation of deformation twins, phase transitions, and reversible processes. This naturally implies a similar behavior at the crack tip in other highly concentrated solid-solution alloys, including high-medium-entropy alloys, providing important insights that greatly improve the understanding of the fracture toughness of metallic materials. Several unconventional and seldom-reported deformation modes are observed at the crack tip of AuCu alloy nanocrystals, including the random generation of hexagonal close-packed (HCP) 2H and 4H phases, recurrence of the reversible face-centered cubic-HCP phase transition, and nanotwins (T), which originates from the chemical inhomogeneity induced by the solid-solution atoms in the AuCu alloy.image
Keyword ：
phase transition phase transition chemical inhomogeneity chemical inhomogeneity crack tip crack tip deformation twin deformation twin in situ in situ
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| GB/T 7714 | Yang, Chengpeng , Fu, Libo , Ma, Yan et al. In Situ Atomic-Scale Evidence of Unconventional Plastic Behavior at The Crack Tip in AuCu Nanocrystals [J]. | ADVANCED FUNCTIONAL MATERIALS , 2023 , 34 (4) . |
| MLA | Yang, Chengpeng et al. "In Situ Atomic-Scale Evidence of Unconventional Plastic Behavior at The Crack Tip in AuCu Nanocrystals" . | ADVANCED FUNCTIONAL MATERIALS 34 . 4 (2023) . |
| APA | Yang, Chengpeng , Fu, Libo , Ma, Yan , Wang, Zhanxin , Li, Dongwei , Shao, Ruiwen et al. In Situ Atomic-Scale Evidence of Unconventional Plastic Behavior at The Crack Tip in AuCu Nanocrystals . | ADVANCED FUNCTIONAL MATERIALS , 2023 , 34 (4) . |
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Abstract ：
非共格孪晶界(incoherent twin boundary,ITB)是金属中一种重要的晶界结构,其原子层次结构对金属的力学性能有显著影响.之前虽有一些关于ITB的结构演化及动态行为研究报道,但ITB与全位错相互反应导致ITB结构变化的原位研究还很少见,相关的原子层次机制仍然不清楚.本文以具有高密度生长孪晶的Pt薄膜为研究对象,利用高角环形暗场像揭示了Pt薄膜中ITB的原子结构.在原子层次原位观察到了全位错向ITB运动靠近,然后被ITB吸收的过程.原子尺度的位移分布测量表明全位错向ITB靠近的过程中就会引起ITB结构的变化.分子动力学模拟以及能量计算结果揭示出全位错容易被ITB吸引,然后形成了新的ITB结构而降低系统能量,这一结果很好地解释了这种新ITB结构在生长的薄膜中经常被观察到的原因.
Keyword ：
原位 原位 非共格孪晶界 非共格孪晶界 Pt薄膜 Pt薄膜 原子尺度 原子尺度 高角环形暗场像 高角环形暗场像 全位错 全位错
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| GB/T 7714 | 郭谊忠 , 李帅 , 王占鑫 et al. 单晶Pt中位错与非共格孪晶界反应的原位原子尺度观察 [J]. | 电子显微学报 , 2022 , 41 (4) : 363-369 . |
| MLA | 郭谊忠 et al. "单晶Pt中位错与非共格孪晶界反应的原位原子尺度观察" . | 电子显微学报 41 . 4 (2022) : 363-369 . |
| APA | 郭谊忠 , 李帅 , 王占鑫 , 李雪峤 , 王立华 , 韩晓东 . 单晶Pt中位错与非共格孪晶界反应的原位原子尺度观察 . | 电子显微学报 , 2022 , 41 (4) , 363-369 . |
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Abstract ：
与传统块体金属材料相比，纳米金属材料具有更加优异的物理、化学性能，有着广泛的应用前景。然而，金属纳米材料在服役过程中易氧化，从而严重影响纳米器件的性能，加速器件老化，造成不可挽回的损失。理清金属材料氧化微观过程，提高材料的抗氧化能力是国家重大工程中的重大问题，也是科学家和研究人员研究的重点。过去传统的氧化机制研究大多局限于微米尺度多层氧化膜的形成机制、形成序列、形成原因等因素，缺少对金属材料原位原子尺度动态氧化机制的研究。因此，研究金属纳米材料纳米尺度下的氧化过程，建立一个清晰的原子尺度氧化体系对提高材料抗氧化能力以及设计抗氧化材料的设计和优化具有重要意义。先进原位技术的出现使研究者能够从原子...
Keyword ：
原子尺度 原子尺度 氧化 氧化 金属 金属 原位 原位
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| GB/T 7714 | 裴星飞 , 王立华 , 陈艳辉 . 纳米金属材料原位氧化电子显微学研究进展 [J]. | 材料导报 , 2022 , 36 (S1) : 500-509 . |
| MLA | 裴星飞 et al. "纳米金属材料原位氧化电子显微学研究进展" . | 材料导报 36 . S1 (2022) : 500-509 . |
| APA | 裴星飞 , 王立华 , 陈艳辉 . 纳米金属材料原位氧化电子显微学研究进展 . | 材料导报 , 2022 , 36 (S1) , 500-509 . |
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Abstract ：
In situ atomic-scale bending tests of twin-structured Ni nanowires were realised using a homemade deformation device. The results showed that the plastic deformation mechanism in twin-structured Ni nanowires depended on the deformation stage. At the early stages of bending deformation, the plasticity of twin-structured Ni nanowires was controlled by dislocations interacting with the twin boundaries or parallel to them. With increasing bending strain, both dislocation and face-centred cubic-body-centred tetragonal phase transition occurred. At very high bending strain, grain boundaries resulting from the lattice distortion/collapse were formed. This study details the deformation mechanisms of the twin-structured Ni nanowires under bending deformation, which advances the basic understanding of the plasticity mechanisms in metals.
Keyword ：
nanowire nanowire twin-structured twin-structured phase transitions phase transitions plastic deformation plastic deformation lattice distortion lattice distortion
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| GB/T 7714 | Zhang, Zihao , Yang, Chengpeng , Guo, Yizhong et al. Direct Observation of the Deformation Mechanism of Twin-Structured Ni NWs under Bending Strain [J]. | METALS , 2022 , 12 (10) . |
| MLA | Zhang, Zihao et al. "Direct Observation of the Deformation Mechanism of Twin-Structured Ni NWs under Bending Strain" . | METALS 12 . 10 (2022) . |
| APA | Zhang, Zihao , Yang, Chengpeng , Guo, Yizhong , Li, Xuegiao , Kong, Deli , Lu, Yan et al. Direct Observation of the Deformation Mechanism of Twin-Structured Ni NWs under Bending Strain . | METALS , 2022 , 12 (10) . |
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Abstract ：
Understanding the deformation behavior of crack tips in metals is of great significance for improving fracture toughness. However, how crack tips in nanosized metallic alloys behave under loading is unclear, because most previous studies focused on pure metals. In this study, the atomic-scale deformation behavior of the crack tip in AuAg alloy nanocrystals was observed in situ. We revealed that the deformation mechanism near the crack tip depended on the distance from the tip. For the 'near region' close to the crack tip, plastic deformation was governed by partial dislocations, twinning, and their interactions. For the 'far region', further than -15 nm from the crack tip, full dislocations dominated, and their interactions resulted in Lomer-dislocation (LD) lock formation and destruction. We uncovered that the combination of blunting dislocation-twin interactions, twin-twin intersections, and formation and destruction of LD locks, as a previously unrecognized fracture toughness improvement mechanism in metals.
Keyword ：
Crack propagation Crack propagation Twinning Twinning In situ transmission electron microscopy In situ transmission electron microscopy Dislocation Dislocation AuAg nanocrystal alloy AuAg nanocrystal alloy
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| GB/T 7714 | Yang, Chengpeng , Fu, Libo , Guo, Yizhong et al. In situ observation of distance dependence of the plasticity behavior of the crack tip in nanosized AuAg alloys [J]. | MATERIALS CHARACTERIZATION , 2022 , 194 . |
| MLA | Yang, Chengpeng et al. "In situ observation of distance dependence of the plasticity behavior of the crack tip in nanosized AuAg alloys" . | MATERIALS CHARACTERIZATION 194 (2022) . |
| APA | Yang, Chengpeng , Fu, Libo , Guo, Yizhong , Ma, Yan , Li, Dongwei , Wang, Zhanxin et al. In situ observation of distance dependence of the plasticity behavior of the crack tip in nanosized AuAg alloys . | MATERIALS CHARACTERIZATION , 2022 , 194 . |
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Abstract ：
A detailed monitoring of atomic-scale processes accomplishing grain rotation is important for understanding the deformation mechanisms in nanocrystalline metals. However, direct observations have been rare thus far, such that our knowledge about grain rotation has to rely heavily on hypothetical models and simulations. Here, we present in situ atomic-resolution evidence, indicating that the atomic processes accomplishing grain rotation in nanocrystalline Pt depend on the type of grain boundary (GB) separating the rotating grains. The grains around general (mixed) GBs rotate via the Frank-Bilby dislocation activities together with atomic shuffling and disconnection activities, the former being the generation, climb, glide and reaction of GB dislocations, whereas the latter leading to GB migration accompanying the grain rotation. While for the grains with a tilt GB in between: their rotation is accomplished almost entirely via the Frank-Bilby dislocation activities. We also discover that the GB dislocation climb, glide, and reaction often involve the formation and destruction of Lomer-like dislocations. (c) 2022 The Authors. Published by Elsevier Ltd on behalf of Acta Materialia Inc.
Keyword ：
Atomic scale Atomic scale Plastic deformation Plastic deformation In situ transmission electron microscopy In situ transmission electron microscopy Dislocation Dislocation Grain boundary plasticity Grain boundary plasticity
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| GB/T 7714 | Guo, Yizhong , Teng, Jiao , Yang, Guo et al. In situ observation of atomic-scale processes accomplishing grain rotation at mixed grain boundaries [J]. | ACTA MATERIALIA , 2022 , 241 . |
| MLA | Guo, Yizhong et al. "In situ observation of atomic-scale processes accomplishing grain rotation at mixed grain boundaries" . | ACTA MATERIALIA 241 (2022) . |
| APA | Guo, Yizhong , Teng, Jiao , Yang, Guo , Li, Ang , Deng, Yao , Yang, Chengpeng et al. In situ observation of atomic-scale processes accomplishing grain rotation at mixed grain boundaries . | ACTA MATERIALIA , 2022 , 241 . |
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