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Surface diffusivity of atomic deuterium on Ni_3(Al, Ti)(110) surface with and without boron

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中国有色金属学会会刊：英文版 2002年第4期12卷 649-652页

作者： J.l.wang y.w.Chung DepartmentofMaterialsScienceandEngineering RobertR.McCormickSchoolofEngineeringandAppliedScienceNorthwesternUniversityEvanstonIL60208USA DepartmentofMaterialsScienceandEngineering RobertR.McCormic

The electron stimulated desorption was used to measure the surface diffusivity of atomic deuterium on clean and boron modified Ni 3(Al, Ti)(110) surfaces. Boron dosing was performed using a solid state boron ion source. Earlier studies showed that boron dissociates water readily at temperatures as low as 130?K and that the resulting atomic hydrogen is bound to the surface strongly. The surface diffusion coefficient of atomic D on 0.05 monolayer boron modified surface was measured to be about 10 times smaller than that on the clean surface. This slower diffusion of atomic hydrogen may explain why boron improves the ductility of polycrystalline Ni 3Al in moist environments.

关键词：氘原子表面扩散硼 Ni3Al Ni3Ti 金属间化合物

Tensile and cyclic deformation response of friction-stir-welded dissimilar aluminum alloy joints:Strain localization effect

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Journal of Materials Science & Technology 2021年第14期73卷 91-100页

作者： P.l.Niu w.y.l. D.l.Chen State Key laboratory of Solidification Processing Shaanxi Key Laboratory of Friction Welding TechnologiesNorthwestern Polytechnical UniversityXi'an710072.China Department of Mechanical and Industrial Engineering Ryerson University350 Victoria StreetTorontoOntarioM5B2K3Canada

Cyclic deformation behavior of friction-stir-welded dissimilar AA2024-T351 to AA7075-T65 aluminum alloy joints was evaluated via stepwise tests at different strain rates,along with transmission electron microscopy examinations to characterize the precipitates required to assess internal *** backscatter diffraction was employed to observe the inhomogeneous microstructures of the FSwed *** localization appeared in the heat affected zone(HAZ)of AA2024 *** cyclic deformation of 500 cycles at a total strain amplitude of 0.5%,the strength of the dissimilar joints resumed basically to that of AA2024 base *** the AA2024 HAZ was obviously hardened,which should be attributed to the introduced dislocations during cyclic deformation *** hardening capacity of the joints increased with decreasing strain rate.

关键词： Friction stir welding Dissimilar aluminum alloys Strain localization Cyclic hardening Slip irreversibility

Frequency Veering of Rotating Metal Porous Twisted Plate with Cantilever Boundary Using Shell Theory

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Acta Mechanica Solida Sinica 2022年第2期35卷 282-302页

作者： y.y.liu y.X.Hao w.Zhang l.T.liu S.w.yang y.T.Cao College of Mechanical Engineering Beijing Information Science and Technology UniversityBeijing 100192China College of Mechanical Engineering Beijing University of TechnologyBeijing 100124China

The frequency veering of a metal porous rotating cantilever twisted plate with twist angle and stagger angle is *** porous materials may have the characteristics of gradient or uniform distribution along the thickness *** on the classical shell theory,considering the influence of centrifugal force produced by high-speed rotation,the free vibration equations of a rotating cantilever twisted plate are *** the polynomial function and Rayleigh-Ritz method,the natural frequencies and mode shapes of the metal porous cantilever twisted plate in both static and rotating states are *** accuracy of the present theory and calculation results is confirmed by a comparison between them and the results available from the literature and those obtained from *** influences of the thickness ratio,porosity,twist angle,stagger angle and rotational velocity on the frequency veering and mode shape shift of the rotating cantilever twisted plate with porous material under three different distributions are *** should be mentioned that the frequency veering accompanied by mode shape shift occurs in both static and dynamic states.

关键词： Frequency veering Rotating twisted plate Cantilever boundary Metal porous

Natural vibration of cantilever porous twisted plate with variable thickness in different directions

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Defence Technology（防务技术） 2023年第9期27卷 200-216页

作者： y.X.Hao y.y.liu w.Zhang l.T.liu K.C.Sun S.w.yang College of Mechanical Engineering Beijing Information Science and Technology UniversityBeijing100192PR China College of Mechanical Engineering Beijing University of TechnologyBeijing100124PR China

In this paper,the blade is assumed to be a rotating variable thickness cantilever twisted plate structure,and the natural vibrations of variable thickness cantilever twisted plate made of metal porous material are *** is assumed that the thickness of the plate changes along spanwise direction and chordwise direction,respectively,and it changes in both *** classical thin shell theory,the first and second fundamental forms of surface and von Karman geometric relationship are employed to derive the total potential energy and kinetic energy of the cantilever twisted plate,in which the centrifugal force potential due to high rotational speed is ***,according to the Rayleigh-Ritz procedure and applying the polynomial functions which satisfy the cantilever boundary conditions,the dynamic system expressed by equations of motion is reduced to an eigenvalue *** numerical simulation,the frequency curves and the mode shapes of the twisted plate can be obtained to reveal the internal connection between natural vibration and the parameters.A series of comparison studies are performed to verify the accuracy of the present formulation and calculations,in which compared data come from experimental,finite element method and theoretical calculation,*** influence of pre-twist angle,three different forms of thickness taper ratio and rotational speed on natural vibration,mode exchange and frequency veering phenomenon of the system is discussed in *** addition,the approach proposed here can efficiently extract analytical expressions of mode functions for rotating variable thickness cantilever twisted plate structures.

关键词： Porous cantilever twisted plate Variable thickness Natural vibration Frequency veering Mode exchange

Achieving ultrahigh electromechanical properties with high TC in PNN-PZT textured ceramics

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Journal of Materials Science & Technology 2024年第8期175卷 258-265页

作者： Q.wang l.Bian K.li y.C.liu y.l.yang B.yang w.w.Cao School of Instrumentation Science and Engineering Harbin Institute of TechnologyHarbin 150080China Guangdong Provincial Key laboratory of Electronic Functional Materials and Devices Huizhou UniversityHuizhou 516001China Conversion and Storage School of Chemistry and Chemical EngineeringHarbin Institute of TechnologyHarbin 150080China

textured Pb(Ni_(1/3)Nb_(2/3))O_(3)-PbZrO_(3)-PbTiO_(3)(PNN-PZT)ceramics were prepared by templated grain growth(TGG)technique using 0.36PNN-x PZ-(0.64-x)PT(x=0.23,0.25 and 0.27)powder *** template content was derived to achieve the best electromechanical properties of textured *** piezoelectric coefficient d33=1165 pC/N,Curie temperature T_(C)=197℃,longitudinal mode electrome-chanical coupling factor k33=0.86 and a very large effective piezoelectric strain coefficient d_(33)^(*)=2041 pm/V were simultaneously achieved at the morphotropic phase boundary(MPB)composition(x=0.25)with 3 vol.%BaTiO_(3)(BT)*** structures of textured ceramics were analyzed in detail to reveal the origin of these high piezoelectric and electromechanical properties.

关键词： Pb(Ni_(1/3)Nb_(2/3))O_(3)-PbZrO_(3)-PbTiO_(3)(PNN-PZT) ceramics MPB composition Texture engineering Electromechanical properties Domain structure

Influences of Reaction Parameters and Ce Contents on Structure and Properties of Nano-scale Ce-HA Powders

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Journal of Materials Science & Technology 2014年第8期30卷 776-781页

作者： l.J.Sun D.G.Guo w.A.Zhao l.y.wang K.w.Xu State Key laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi'an Jiaotong University Chao Family Comprehensive Cancer Center Department of Pharmaceutical SciencesUniversity of California Irvine Sue and Bill Gross Stem Cell Research Center University of California Irvine The Key laboratory of Bioactive Materials Ministry of EducationCollege of Life SciencesNankai University Xi'an University of Arts and Science

Ce-incorporated apatite（Ce-HA） nano-scale particles with different Ce percentage contents（atomic ratio of Ce to Ce ＋ Ca is 5%,10%and 20%,respectively） were synthesized via a simple wet chemical method in this *** crystal structure,chemical groups,thermal stability,crystal morphologies and crystal sizes of the Ce-HA nano-particles were characterized by X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,and transmission electron microscopy（TEM）.The influences of reaction temperature,reaction time,pH value,and the atomic ratio of Ce to Ce ＋ Ca on the structure and performance of Ce-HA particles were *** results show that the lattice constants,particle sizes,crystallinity and thermal stability of Ce-HA vary with the doped Ce *** the increase of Ce content,the lattice constants of the Ce-HA nano-particles remarkably increase but the particle size,crystallinity and thermal stability gradually *** reaction temperature as well as the reaction time has no significant effect on the properties of the final products,while the pH value has a direct relationship with their final chemical *** obtained Ce-HA nanosize particles possess potential application in preparing artificial bone implants,bone tissue engineering scaffold and other bioactive coatings.

关键词： Cerium Apatite Nano-scale powder wet chemical approach Biomedical materials

Effect of Carbon Nanotube Orientation on Mechanical Properties and Thermal Expansion Coefficient of Carbon Nanotube-Reinforced Aluminum Matrix Composites

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Acta Metallurgica Sinica(English letters) 2014年第5期27卷 901-908页

作者： Z.y.liu B.l.Xiao w.G.wang Z.y.Ma School of Materials Science and Engineering Dalian University of Technology Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences School of Mechanical Engineering Liaoning Shihua University

Carbon nanotube-reinforced 2009Al （CNT/2009Al） composites with randomly oriented CNTs and aligned CNTs were fabricated by friction stir processing （FSP） and FSP-rolling, respectively. The CNT/2009A1 composites with aligned CNTs showed much better tensile properties at room temperature and elevated temperature compared with those with the randomly oriented CNTs, which is mainly attributed to larger equivalent aspect ratio of the CNTs and avoidance of preferential fracture problems. However, much finer grain size was not beneficial to obtaining high strength above 473 K. The aligned CNTs resulted in tensile anisotropy, with the best tensile properties being achieved along the direction of CNT aligning. As the off-axis angle increased, the tensile properties were reduced due to the weakening of the load transfer ability. Furthermore, aligned CNTs resulted in much lower coefficient of thermal expansion compared with randomly oriented CNTs.

关键词： Carbon nanotubes Metal matrix composites Mechanical properties Coefficient of thermalexpansion Friction stir processing

Tensile Strength and Electrical Conductivity of Carbon Nanotube Reinforced Aluminum Matrix Composites Fabricated by Powder Metallurgy Combined with Friction Stir Processing

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Journal of Materials Science & Technology 2014年第7期30卷 649-655页

作者： Z.y.liu B.l.Xiao w.G.wang Z.y.Ma Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences Dalian University of Technology liaoning Shihua University

A route combining powder metallurgy and subsequent friction stir processing was utilized to fabricate carbon nanotube （CNT） reinforced AI （CNT/AI） and 6061AI （CNT/6061AI） composites. Microstructural observations indicated that CNTs were uniformly dispersed in the matrix in both CNT/AI and CNT/6061AI composites. Mg and Si elements tended to segregate at CNT-AI interfaces in the CNT/6061AI composite during artificial aging treatment. The tensile properties of both the AI and 6061AI were increased by CNT incorporation. The electrical conductivity of CNT/AI was decreased by CNT addition, while CNT/6061AI exhibited an increase in electrical conductivity due to the Mg and Si segregation.

关键词： Carbon nanotubes Metal matrix composites Mechanical properties Electrical properties Friction stir processing

OXIDATION RESISTANCE OF NANOCRySTAl ODS AlUMINIDE COATINGS PRODUCED By PACK AlUMINIZING PROCESS ASSISTED By BAll PEENING

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Acta Metallurgica Sinica(English letters) 2006年第3期19卷 215-222页

作者： Z.l. Zhan y.D. He w. Gao Kunming University of Science and Technology Kunming 650093 China Beijing Key laboratory for Corrosion Erosion and Surface Technology University of Science and Technology Beijing Beijing 100083 China Engineering School The University of Auckland Auckland 1020 New Zealand

Nanocrystal ODS （oxide dispersion strengthening） aluminide coatings were produced on a stainless steel and nickel-based superalloy by the pock aluminizing process assisted by ball peening, Pure Al powders and 1% of ultra-fine y2O3 powders were mixed by ball milling. The ultra-fine y2O3 powders were dispersed in Al particles. Ball peening welded the Al particles onto the substrate and accelerated the formation of aluminide coating. Nanocrystal ODS aluminide coatings were produced by the outward growth at a much low temperature （below 600℃） in a short treatment time. The effects of the operation temperature and treatment time on the formation of the coatings were analyzed. SEM （scanning electron microscope）, AFM （atomic force microscope）, EDS （energy dispersive X-ray spectroscopy）, XRF （X-ray fluorescence spectrometer） and XRD （X-ray diffraction） methods were applied to investigate the microstructure of the coatings. High-temperature oxidation tests were carried out to evaluate the oxidation resistance of the ODS aluminide coatings.

关键词： nano-coating ODS coating aluminide coating ball peening high-temperature oxidation