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Quantitative Electron Tomography for Accurate Measurement of Precipitates Microstructure Parameters in Al–Cu–Li Alloys

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Acta Metallurgica Sinica(English Letters) 2022年第11期35卷 1882-1894页

作者： Shi-Yong Li Ruo-Han Shen Yu-Tao He cui-lan wu Jiang-Hua Chen Centre for High Resolution Electron Microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China College of Materials Science and Engineering Hainan UniversityHaikou 570228China

Mechanical theories show that properties of alloys are strongly dependent on the morphological parameters oftheir strengthening ***,accurate measurement of precipitates microstructure parameters is still a challenging *** this article,we develop a quantitative electron tomography method by combining computer vision technology to accurately characterize the three-dimensional microstructure parameters,such as volume fractions,sizes and distributions,of the T_(1) and δ’/θ’/δ’ precipitates in Al-Cu-Li(-Mg) *** they have extremely large aspect-ratios in shape and large numbers in density upon formation in the Al matrix,these thin plate-like precipitates are difficult to be characterized quantitatively without the assistance of computer vision *** is shown that the property difference between two peak-aged states of the alloy can be well explained with the quantitative precipitate parameters correctly *** these correct precipitate data,we also tested the validity of current mechanical models for projecting the contribution of precipitates to the strengths of the alloy,demonstrating that quantitative relations between strength and micro structure parameters still need to be refined.

关键词： Al–Cu–Li–Mg alloy T1 precipitate δ′/θ′/δ′composite precipitate Morphological parameters Electron tomography Computer vision

Complex Precipitation Sequences of Al-Cu-Li-(Mg)Alloys Characterized in Relation to Thermal Ageing Processes

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Acta Metallurgica Sinica(English Letters) 2016年第1期29卷 94-103页

作者： Zhen Gao Jiang-Hua Chen Shi-Yun Duan Xiu-Bo Yang cui-lan wu Center for High-Resolution Electron Microscopy College of Materials Science and EngineeringHunan University

The A1-Cu-Li-（Mg） alloy is a high-performance lightweight material strengthened by complex coexisting precipitates that form in the alloy upon thermal ageing. Using high-resolution （scanning） transmission electron microscopy in association with first-principles energy calculations, we systematically studied the complex coexisting precipitates in the alloys and correlated their precipitation sequences with thermal ageing processes applied. The principal results are the following：（1） eight types of precipitates can be observed in the alloy; （2） of these precipitates, the Tl-phase is most stable. The S-phase precipitates with segregated Li atoms at their interfacial edges are unexpectedly more stable than the a-phase; （3） the Tl-phase has a characteristic precursor that plays the key role in its nucleation and growth.

关键词： AI-Cu-Li alloy Electron microscopy Ageing Precipitation Strength

Synergistic Effect of Alloying Atoms on Intrinsic Stacking-Fault Energy in Austenitic Steels

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Acta Metallurgica Sinica(English Letters) 2017年第3期30卷 272-279页

作者： Ling-Hong Liu Tou-Wen Fan cui-lan wu Pan Xie Ding-Wang Yuan Jiang-Hua Chen Center for High-Resolution Electron Microscopy College of Materials Science and Engineering Hunan UniversityChangsha 410082 China College of Science Central South University of Forestry and Technology Changsha 410004 China Hunan Province Key Laboratory for Spray Deposition Technology and Application Hunan University Changsha 410082 China

Intrinsic stacking-fault energy is a critical parameter influencing the various mechanical performances of aus- tenitic steels with high Mn concentrations. However, quantitative calculations of the stacking-fault energy （SFE） of the face-centered cubic （fcc） Fe, including the changes in concentrations and geometrical distribution of alloying atoms, cannot be obtained by using previous computation models. On the basis of the interaction energy model, we evaluated the effects of a single alloying atom （i.e., Mn, A1, Si, C and N）, as well as its aggregates, including the Mn-X dimer and Mn2-X trimer （X = A1, Si, C and N） on the SFE of the fcc Fe via first-principle calculations. Given low concentrations （〈10 wt%） of alloying atoms, dimers and trimers, theoretical calculations reveal the following：（1） Alloying atom Mn causes a decrease in the SFE, whereas A1, Si, C and N significantly increase the SFE; （2） combination with other alloying atoms to form the Mn-X dimer （X = A1, Si, C and N） exerts an effect on SFE that, to a certain extent, is close to that of the corresponding single X atom; （3） the interaction between Mnz-X and the stacking fault is stronger than that of the corresponding single X atom, inducing a significant increase in the SFE of fcc Fe. The theoretical results we obtained demonstrate that the increase in SFE in high-Mn steel originates from the synergistic effect of Mn and other trace alloy atoms.

关键词： Stacking-fault energy Synergism First-principle calculation Austenitic steel Alloying effect

Elastic Properties and Stacking Fault Energies of Borides, Carbides and Nitrides from First-Principles Calculations

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Acta Metallurgica Sinica(English Letters) 2019年第9期32卷 1099-1110页

作者： Yong Zhang Zi-Ran Liu Ding-Wang Yuan Qin Shao Jiang-Hua Chen cui-lan wu Zao-Li Zhang Center for High-Resolution Electron Microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China Department of Physics Key Laboratory for Low-Dimensional Structures and Quantum Manipulation(Ministry of Education)Hunan Normal UniversityChangsha 410086China Erich Schmid Institute of Materials Science Austrian Academy of SciencesJahnstraBe 128700 LeobenAustria

Owing to the excellent elastic properties and chemical stability,binary metal or light element borides,carbides and nitrides have been extensively applied as hard and low-compressible *** are searching for harder materials all the ***,the successful fabrication of nano-twinned cubic BN(Tian et *** 493:385–388,2013)and diamond(Huang et *** 510:250–253,2014)exhibiting superior properties than their twin-free counterparts allows an efficient way to be *** this point of view,the borides,carbides and nitrides may be stronger by introducing twins,whose formation tendency can be measured using stacking fault energies(SFEs).The lower the SFEs,the easier the formation of *** the present study,by means of first-principles calculations,we first calculated the fundamental elastic constants of forty-two borides,seventeen carbides and thirty-one nitrides,and their moduli,elastic anisotropy factors and bonding characters were accordingly ***,the SFEs of the{111}glide system of twenty-seven compounds with the space group F43 m or Fm3m were *** on the obtained elastic properties and SFEs,we find that(1)light element compounds usually exhibit superior elastic properties over the metal borides,carbides or nitrides;(2)the 5 d transitionmetal compounds(ReB2,WB,OsC,RuC,WC,OsN2,TaN and WN)possess comparable bulk modulus(B)with that of cBN(B=363 GPa);(3)twins may form in ZrB,HfN,PtN,VN and ZrN,since their SFEs are lower or slightly higher than that of diamond(SFE=277 mJ/m^2).Our work can be used as a valuable database to compare these compounds.

关键词： Inorganic compounds Elastic properties Stacking fault energies First-principles calculations

Application of the Peierls–Nabarro Model to Symmetric Tilt Low-Angle Grain Boundary with Full Dislocation in Pure Magnesium

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Acta Metallurgica Sinica(English Letters) 2016年第11期29卷 1053-1063页

作者： Tou-Wen Fan Xiu-Bo Yang Jiang-Hua Chen Ling-Hong Liu Ding-Wan Yuan Yong Zhang cui-lan wu Center for High-Resolution Electron Microscopy College of Materials Science and Engineering Hunan University Department of Applied Physics School of Physics and Electronics Hunan University Hunan Province Key Laboratory for Spray Deposition Technology and Application Hunan University College of Science Central South University of Forestry and Technology

Three types of symmetric （1120） tilt low-angle grain boundaries （LAGBs） with array of basal, prismatic, and pyramidal edge full 〈a〉 dislocations in pure Mg have been studied by using the improved Peierls-Nabarro model in combination with the generalized stacking fault energy curve. The results show that with decreasing distance between the dislocations in all the three types of tilt LAGBs, the stress and strain fields are gradually suppressed. The reduction extent of the stress and strain fields decreases from the prismatic to basal to pyramidal dislocations. The variation of dislocation line energy （DLE） for all tilt LAGBs is divided into three stages： DLE changes slightly and linearly when the distance is larger than 300 A, - 10%; DLE declines exponentially and quickly when the distance goes from 300 to 100 A, ,- 70%; and finally, the descent speed lowers when the distance is smaller than 100 A and the dislocation core energy is nearly half of the DLE. The grain boundary energy （GBE） decreases when the tilt angle of LAGB increases from1 ° to 2° for all cases. The tilt LAGB consists of pyramidal dislocations always has the largest GBE, while that with array of prismatic dislo- cations has the smallest one in the whole range. The Peierls stress of dislocation in tilt LAGB is nearly unchanged, the same as that of single dislocation. This work is useful for further study of dissociated dislocation, solute segregation, precipitate nucleation in tilt LAGB and its interaction with single dislocations.

关键词： Tilt grain boundary Generalized stacking fault energy Magnesium alloy Dislocation Peierlsstress

Revisiting the Hierarchical Microstructures of an Al-Zn-Mg Alloy Fabricated by Pre-deformation and Aging

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Acta Metallurgica Sinica(English Letters) 2020年第11期33卷 1518-1526页

作者： Xiong-Wei Yu Jiang-Hua Chen Wen-Quan Ming Xiu-Bo Yang Tian-Tian Zhao Ruo-Han Shen Yu-Tao He cui-lan wu Center for High-Resolution Electron Microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

Pre-deformation before aging has been demonstrated to have a positive effect on the mechanical strength of the 7N01 alloy in our previous study,which is rather different from the general negative effects of pre-deformation on high-strength 7XXX aluminum *** order to explain the strengthening mechanism relating to the positive effect,in the present study,the microstructure of the aged 7N01 alloy with different degrees of pre-deformation was investigated in detail using advanced electron microscopy *** results show that,without pre-deformation,the aged alloy is strengthened mainly by the η′type of hardening *** contrast,with pre-deformation,the aged alloy is strengthened by the hierarchical microstructure consisting of the GP-η′type of precipitates formed inside sub-grains,the ηp type of precipitates formed at small-angle boundaries,and the dislocation introduced by pre-deformation(residual work-hardening effect).By visualizing the distribution of theηp precipitates through three-dimensional electron tomography,the 3 D microstructures of dislocation cells are clearly *** combinations of ηp precipitates,GP-η′precipitates and residual dislocations in the alloy are responsible for the positive effect of pre-deformation on its mechanical properties.

关键词： Aluminum alloys Precipitates Pre-deformation Three-dimensional electron tomography(3DET) Dislocation cell

Thermal stability and precipitate microstructures of Al−Si−Mg−Er alloy

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Transactions of Nonferrous Metals Society of China 2021年第1期31卷 1-10页

作者： Yi HE Hai-hui XI Wen-quan MING Qin-qin SHAO Ruo-han SHEN Yu-xiang LAI cui-lan wu Jiang-hua CHEN College of Materials Science and Engineering Hunan UniversityChangsha 410082China

The effect of Er on the microhardness and precipitation behavior of the heat-treated Al−Si−Mg alloy was investigated by microhardness tester and *** a comparison,the influence of natural aging was also *** is shown that the thermal stability of the over-aged Al−Si−Mg−Er alloy is highly related to the average size of the *** average size ofβ''precipitates in Al−Si−Mg−Er alloy is smaller than that in Al−Si−Mg alloy,and the distribution is more localized under condition of without introducing natural ***,when natural aging is introduced before artificial aging,the Al−Si−Mg−Er alloy has similar average size and distribution of precipitates with the Al−Si−Mg alloy,resulting in similar mechanical *** effect of Er on the precipitation kinetics in the alloy was also discussed in detail to explain these phenomena.

关键词： Al−Si−Mg alloy Er natural aging precipitate thermal stability

A GNSS Anti-Spoofing Technique Based on the Spatial Distribution Characteristic of the Residual Vectors

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Tsinghua Science and Technology 2024年第2期29卷 457-468页

作者： Qi'an wu Xiaowei cui Mingquan Lu Pengxiang Yang Peng wu Department of Electronic Enginnering Tsinghua UniversityBeijing 100084China Xi’an Modern Control Technology Research Institute Xi’an 710065China

Anti-spoofing is becoming a crucial technique for applications with high navigation accuracy and reliability ***-spoofing technique based on Receiver Autonomous Integrity Monitoring(RAIM)is a good choice for most Global Navigation Satellite System(GNSS)receivers because it does not require any change to the hardware of the ***,the conventional RAIM method can only detect and mitigate a single spoofing *** improved RAIM methods can deal with more spoofing signals,but the computational complexity increases dramatically when the number of satellites in view increase or need additional *** paper proposes a new RAIM method,called the SRV-RAIM method,which has a very low computation complexity regardless of the number of satellites in view and can deal with any number of spoofing *** key to the new method is the spatial distribution characteristic of the Satellites'Residual Vectors(SRV).In replay or generative spoofing scenarios,the pseudorange measurements of spoofing signals are consistent,the residual vectors of real satellites and those of spoofing satellites have good separation characteristics in spatial *** on this characteristic,the SRV-RAIM method is proposed,and the simulation results show that the method can separate the real signals and the spoofing signals with an average probability of 86.55%in the case of 12 visible satellites,regardless of the number of spoofing *** to the conventional traversal-RAIM method,the performance is only reduced by 3.59%,but the computational cost is reduced by 98.3%,so most of the GNSS receivers can run the SRV-RAIM algorithm in time.

关键词： Global Navigation Satellite System(GNSS) anti-spoofing Receiver Autonomous Integrity Monitoring(RAIM) Satellites'Residual Vectors(SRV)

Nanoparticle targeting cGAS-STING signaling in disease therapy

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Nano Research 2024年第8期17卷 7315-7336页

作者： lan Zhou Yu Huang Yuzhang wu Shupei Tang Frontier Medical Training Brigade Third Military Medical UniversityHutubi 831200China Department of Gastroenterology Xinqiao HospitalThird Military Medical UniversityChongqing 400037China Institute of Immunology Third Military Medical UniversityChongqing 400038China Shigatse Branch Xinqiao HospitalThird Military Medical UniversityShigatse 857000China

The cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon(IFN)genes(cGAS-STING)signaling pathway is crucial for sensing abnormal DNA accumulation in the *** binds to abnormal DNA,cGAS catalyzes the production of second messenger cyclic dinucleotides,followed by the activation of downstream *** activation induces the expression of type I interferon and other inflammatory cytokines,ultimately initiating an immune *** to the involvement of the cGAS-STING pathway in various diseases,including infection,tumor,autoimmune disease and kidney disease,ongoing research is focused on developing drugs and treatment methods to target and regulate this *** the development of nanotechnology,nanomedicines targeting cGAS-STING signaling are of great significance in clinical applications due to their targeted delivery,controlled drug release,improved solubility,multifunctionality,and enhanced *** comprehensive review focuses on the most recent progress of nanoplatforms targeting cGAS-STING in disease therapy,aiming to provide references and guidelines for further design and optimization of nanomedicines.

关键词： nanomedicine cGAS-STING pathway and related disease anti-tumor nanotherapy anti-viral nanotherapy