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Transformation Mechanism of (γ+γ') and the Effect of Cooling Rate on the Final Solidification of U720Li Alloy

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Acta Metallurgica Sinica(English Letters) 2017年第9期30卷 887-894页

作者： Guang-Di zhao Guo-Liang Yang fang liu Xin Xin Wen-Ru Sun Institute of Metal Research Chinese Academy of Sciences School of Materials Science and Engineering University of Science and Technology of China

The transformation mechanism of （γ ＋γ′） was studied by analyzing the microstructure and elemental distri- bution of the U720Li samples heated at 1250℃ and cooled at the rates in the range of 1-100℃/s. Although the （γ ＋γ′） is deemed to be formed by a eutectic reaction and has been called eutectic （γ ＋γ′）, it was found in the present study that the （γ ＋γ′） precipitation begins with a peritectic reaction of （L ＋ γ）γ′, and develops by the eutectic reaction of L （γ ＋γ′）. The energy for the γ′ nucleation is low because the interfacial energy for the γ /γ′ interface is about one-tenth of the solid/liquid interface, and hence, the nucleation rate is high and the fine structure of （γ ＋ γ′） is formed at the initial precipitation stage. The γ and γ′ in （γ ＋ γ′） tend to grow into a lamellar structure because it is difficult for them to nucleate directly from the residual liquids, and hence, the γ′ precipitates naturally tend to grow divergently direction of the regions rich in AI and Ti, forming a fan-like structure of the （γ ＋γ′）. As a result, the γ′ precipitates will coarsen finally because the space between them is enlarged. The solidification of the final residual liquids is a diffusion dependent process. When cooled at a higher rate, a higher degree of super cooling is reached and finally the solidification is finished by the pseudo- eutectic reaction of L → （γ ＋ boride） and L→ （γ ＋γ′）, which can absorb Zr and B. When cooled at a rate low enough, most of the residual liquids are consumed by the （γ ＋γ′） growth due to the sufficient diffusion, and the boride and Zr- bearing phase are precipitated at a quasi-equilibrium state. Under this condition, Ti is depleted at the （γ ＋γ′） growth front. However, the η-Ni3Ti phase is formed there occasionally due to the boride precipitation, because the compositions of the two phases are complementary.

关键词： U720Li (γ +γ′) formation mechanism Cooling rate Solidification

THIN FILMS Bi(Pb)-Sr-Ca-Cu-O (Tc (zero)=105K) PREPARED BY ION BEAM SPUTTERING

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Chinese Physics Letters 1990年第10期7卷 461-464页

作者： ZHOU Ping DONG Ziwen liu Guirong YANG Qiansheng zhao Zhongxian Institute of Physics Academia SinicaBeijing 100080

High temperature superconducting Bi(Pb)-Sr-Ca-Cu-O thin films have been deposited onto single crystals(100)MgO substrates heated at 400℃ by ion beam sputtering and were post annealed in *** film properties are sensitive to the annealing *** best films show an onset transition temperature of approximately 120K and zero resistance at 105K.X-ray diffraction shows the films to have high c-axis orientation with a high Tc *** composition of film was determined by inductively coupled plasma-atomic emission spectrometry analysis,and their morphology was observed by scanning electron microscopy.

关键词： resistance film heated

A Modifi ed Molecular Structure Mechanics Method for Analysis of Graphene

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Journal of Wuhan University of Technology(Materials Science) 2015年第6期30卷 1172-1178页

作者：华军 LI Dongbo zhao Dong LIANG Shengwei liu Qinlong JIA Ruiyan Department of Mechanics School of Science Xi'an University of Architecture and Technology

Based on molecular mechanics and the deformation characteristics of the atomic lattice structure of graphene, a modifi ed molecular structure mechanics method was developed to improve the original one, that is, the semi-rigid connections were used to model the bond angle variations between the C-Cbonds in graphene. The simulated results show that the equivalent space frame model with semi-rigid connections for graphene proposed in this article is a simple, efficient, and accurate model to evaluate the equivalent elastic properties of graphene. Though the present computational model of the semi-rigid connected space frame is only applied to characterize the mechanical behaviors of the space lattices of graphene, it has more potential applications in the static and dynamic analyses of graphene and other nanomaterials.

关键词： graphene molecular structure mechanics semi-rigid connections mechanical properties

Microstructural Feature and Evolution of Rapidly Solidified Ni3Al-Based Superalloys

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Acta Metallurgica Sinica(English Letters) 2019年第6期32卷 764-770页

作者： Ye-fan Li Chong Li Jing Wu Hui-Jun Li Yong-Chang liu Hai-Peng Wang State Key Lab of Hydraulic Engineering Simulation and Safety School of Materials Science and EngineeringTianjin UniversityTianjin 300354China Department of Applied Physics School of ScienceNorthwestern Polytechnical UniversityXi'an 710129China

The Ni3Al-based superalloy was rapidly solidified in the form of droplets with varying *** cooling rate(Rc)is a function of diameter(D)of *** the decrease in droplet sizes(increase in the cooling rates),the volume fraction ofγ’+γeutectic structure increases from 21.31(D=1400 lm,Rc=3.6 9 102 K s-1)to 36.31%(D=270 lm,Rc-=2.3 9 103 K s-1).Moreover,unimodal size distribution of nano-γ’exists in the droplets instead of bimodal dual-size distributions ofγprecipitates that are normal in as-cast alloys.

关键词： Ni3Al-based superalloy Microstructure Rapid solidification γ’precipitate

Creep Behaviors of FGH95 Powder Ni-Base Superalloy

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Chinese Journal of Aeronautics 2009年第4期22卷 444-448页

作者： Tian Sugui liu Yang Zhou Xiaoming zhao Zhonggang Bao Xianyu Wang Wuxiang School of Materials Science and Engineering Shenyang University of Technology Shenyang 110023 China Beijing Institute of Aeronautical Materials Beijing 100095 China

This article makes an investigation into the creep behavior and deformation features of FGH95 powder Ni-base superalloy by means of creep curves and microstructural observation. Results show that this superalloy exposes obvious sensibility to the applied temperature and stresses in the experimental range. Microstructure of the alloy consists of γ＇ phase of various sizes and dispersed carbide particles precipitated in the wider crystal boundaries between the powder particles. During the creep, the deformation of the alloy occurs in the form of singleor double-oriented slipping inside the grains, and some of the finer carbide particles are precipitated near the slipping traces. The wide grain boundaries might be broken into the finer grains due to severe deformation. The deformation mechanism of the alloy during creep is thought to be the activation of dislocations of double-oriented slipping, including （1/2）〈 110〉 dislocation inside the γ matrix phase and 〈110〉 super-dislocation inside the γ＇phase. The formation of the stacking faults and （1/3）〈112〉 super-Shockleys partial dislocation configuration is attributed to the decomposition of 〈 110〉 super-dislocation in the γ＇ phase.

关键词： FGH95 powder Ni-base superalloy microstructure creep deformation features

Effects of Si^3＋ and H＋ Irradiation Friction on Tungsten Evaluated by Internal Method

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Plasma Science and Technology 2013年第10期15卷 1071-1075页

作者： HU Jing ZHANG Yanwen WANG Xianping zhao Ziqiang fanG Qianfeng liu Changsong Key Laboratory of Materials Physics Institute of Solid State PhysicsChinese Academy of Sciences Hefei 230031 China State Key Laboratory of Nuclear Physics and Technology Peking UniversityBeijing 100871 China

Effects of Si^3＋ and H＋ irradiation on tungsten were investigated by internal friction （IF） technique. Scanning electron microscope （SEM） analysis revealed that sequential dual Si＋H irradiation resulted in more serious damage than single Si irradiation. After irradiation, the IF background was significantly enhanced. Besides, two obvious IF peaks were initially found in tem- perature range of 70～330 K in the sequential Si＋H irradiated tungsten sample. The mechanism of increased IF background for the irradiated samples was suggested to originate from the high density dislocations induced by ion irradiation. On the other hand, the relaxation peak PL and non-relaxation peak PH in the Si＋H irradiated sample were ascribed to the interaction process of hydrogen atoms with mobile dislocations and transient processes of hydrogen redistribution, respectively. The obtained experimental results verified the high sensitivity of IF method on the irradiation damage behaviors in nuclear materials.

关键词： tungsten irradiation damage internal friction hydrogen-dislocation interac-tion

Wideband radar cross-section reduction using plasma-based checkerboard metasurface

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Plasma Science and Technology 2022年第8期24卷 98-104页

作者： Zhiming zhao Xiaoping LI Guoxiang DONG Yanming liu School of Aerospace Science and Technology Xidian UniversityXi'an 710126People's Republic of China

For stealth technology,in order to overcome the limitations of thin-layer plasma for electromagnetic waves attenuation and further broaden the radar cross-section(RCS)reduction(RCSR)band of the metasurface,the plasma-based checkerboard metasurface composed of plasma and checkerboard metasurface is investigated to achieve better *** designed a checkerboard metasurface which can achieve abnormal reflection to reduce RCS and whose-10d B RCSR bandwidth is from 8.1 to 14.5 GHz,the RCSR principle of it lies in the backscattering cancellation,which depends on the phase difference of artificial magnetic conductor(AMC)*** designed plasma-based checkerboard metasurface is a thin composite structure,including a checkerboard metasurface,a plasma layer,and an air gap which is between *** wave simulations confirm that the plasma-based checkerboard metasurface’s–10 dB RCS reduction bandwidth and RCS reduction amplitude,are both increased under different polarized waves compared with the only single plasma or the only *** also introduced the reason and mechanism of the interaction between plasma and the checkerboard metasurface to improve the RCSR effect in *** plasma-based checkerboard metasurface does not need the plasma to be too thick for plasma stealth,its application in practical scenarios is easier to implement.

关键词： abnormal reflection plasma-based checkerboard metasurface radar cross section reduction(RCSR) stealth technology

A planetary companion orbiting the intermediate-mass G Giant HD 173416

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Chinese Journal of Astronomy and Astrophysics 2009年第1期9卷 1-4页

作者： Yu-Juan liu Bun＇ei Sato Gang zhao Hiroyasu Ando National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Tokyo Institute of Technology 2-12-10okayama Meguro-ku Tokyo 152-8550 Japan National Astronomical Observatory of Japan National Institutes of Natural Sciences 2-21-1 Osawa Mitaka Tokyo 181-8588 Japan Deparfment of Astronomy Graduate University for Advanced Studies Shonan Village Hayama Kanagawa 240-0193 Japan

The discovery of a planetary companion to the intermediate-mass late-type giant star HD173416 from precise Doppler surveys of G and K giants at Xinglong station and Okayama Astrophysical Observatory （OAO） is presented in this letter. The planet has a minimum mass of 2.7 MJ, an eccentricity of 0.21, a semimajor axis of 1.16 AU and an orbital period of 324 days.

关键词： planetary systems -- stars individual HD173416 - stars PlanetarySystems -- techniques: radial velocities

Decoding algorithms of single photon counting imager based on two-dimensional Vernier anodes

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Science China(Physics,Mechanics & Astronomy) 2011年第11期54卷 1943-1947页

作者： YANG Hao zhao BaoSheng YAN QiuRong liu YongAn HU HuiJun State Key Laboratory of Transient Optics and Photonics Xi ＇an Institute of Optics and Precision Mechanics Chinese Academy of Sciences Xi＇an 710119 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

The decoding algorithms of two-dimensional Vernier anodes are deduced *** precision of decoding and uniqueness of encoding are *** influencing factors of detection sensitivity and spatial resolution are *** single photon imaging system is constructed,and the two-dimensional Vernier collector is *** image of the ultra-weak emission source is *** spatial resolution of the system is about 100μm.

关键词： decoding algorithms photon counting imaging Vernier collector influencing factors