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Magnetic/Magnetostrictive Properties Together with Resistivity and Corrosion Behaviors of CoFe_2 and Its Composite with CoFe_2N

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Journal of Materials Science & Technology 2017年第7期33卷 744-750页

作者： B.q.Geng y.q.Ma M.Wang Z.L.Ding W.H.Song B.C.Zhao Key Laboratory of Materials Physics Institute of Solid State Physics Chinese Academy of Sciences Hefei 230031 China

The CoFe_2alloy（CF） was prepared by reducing CoFe_2O_4 in the H_2 ambient. Subsequently the CF sample was nitrided in the NH_3 atmosphere to produce the composite of CoFe_2N and CoFe_2. The magnetostriction, thermal expansion, resistivity and corrosion resistance of CF sample and the nitrided sample（CFN）at 1000？C were investigated. The saturation magnetostriction coefficiency λ_s and thermal expansion coefficient ？ at 300 K for the nitrided CFN were 50 ppm and 10 ppm/K, respectively, approximately equal to those for the CF sample. However, compared with CF, CFN presents a decrease in temperature coefficient R_λ（300 K） of magnetostriction by 11%. The smaller resistivity and improved corrosion resistance in the H_2SO_4 solution may expand the applications of the CoFe_2 in the fields needing lower resistivity or in the acidic environment.

关键词： CoFe alloy CoFe_2N alloy Magnetostriction Resistivity Corrosion resistance

ELECTROCheMICAL NOISE ANALySIS OF The INFLUENCE OF The Zn^(2+)IONS CONCENTRATION ON ZINC ELECTROPLATING

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Acta Metallurgica Sinica(English Letters) 2005年第2期18卷 137-144页

作者： Z.Zhang C.S.Wu q.y.Cai F.H.Cao J.q.Zhang DepartmentofChemistry ZhejiangUniversityHangzhou310027China DepartmentofChemistry ZhejiangUniversityHangzhou310027China／／StateKeyLaboratoryforCorrosionandProtectionInstituteofMetalResearchTheChineseAcademyofSciencesShenyang110016China

The influence of the concentration of Zn2+ ions on zinc electroplating process was investigated by means of electrochemical noise (EN) and cyclic voltammetry methods in conjunction with the scanning electron microscopy (SEM) technique. It was found that the EN generated during the electroplating of dentritic or large polymeric zinc deposit has large potential oscillation amplitude and positive potential drift while the compact zinc deposit possesses small noise amplitude and little potential drift. With the change of rate determining step from diffusion-control through mixed-control to activation-control, the maximum relative energy obtained from wavelet analysis defined from the region with larger scales to those with smaller scales, and the EDP (relative energy distribution plot) can be us, as 'fingerprints' of EN to characterize the electroplating process and the deposit structure. The results also showed that electrochemical noise technique can give more information about the electrodeposit structure than other normal electrochemical measurements, such as linear potential sweep method and cyclic voltammetry technique.

关键词： zinc electroplating zinc ions concentration electrochemical noise electrodeposit structure

Timoshenko beam model for chiral materials

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Acta Mechanica Sinica 2018年第3期34卷 549-560页

作者： T.y.Ma y.N.Wang L.yuan J.S.Wang q.H.qin Department of Mechanics Tianjin University School of Engineering Deakin University Research School of Engineering Australian National University

Natural and artificial chiral materials such as deoxyribonucleic acid （DNA）, chromatin fibers, flagellar filaments, chiral nanotubes, and chiral lattice materials widely exist. Due to the chirality of intricately helical or twisted microstructures, such materials hold great promise for use in diverse applications in smart sensors and actuators, force probes in biomedical engineering, structural elements for absorption of microwaves and elastic waves, etc. In this paper, a Timoshenko beam model for chiral materials is developed based on noncentrosymmetric micropolar elasticity theory. The governing equations and boundary conditions for a chiral beam problem are derived using the variational method and Hamilton＇s principle. The static bending and free vibration problem of a chiral beam are investigated using the proposed model. It is found that chirality can significantly affect the mechanical behavior of beams, making materials more flexible compared with nonchiral counterparts, inducing coupled twisting deformation, relatively larger deflection, and lower natural frequency. This study is helpful not only for understanding the mechanical behavior of chiral materials such as DNA and chromatin fibers and characterizing their mechanical properties, but also for the design of hierarchically structured chiral materials.

关键词： Timoshenko beam model Chiral material Chirality Deflection Microrotation

Unusually high corrosion resistance in Mo_(x)CrNiCo medium entropy alloy enhanced by acidity in aqueous solution

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Journal of Materials Science & Technology 2023年第8期139卷 59-68页

作者： S.Shuang G.J.Lyu D.Chung X.Z.Wang X.Gao H.H.Mao W.P.Li q.F.he B.S.Guo X.y.Zhong y.J.Wang y.yang Department of Mechanical Engineering College of EngineeringCity University of Hong KongKowloon TongKowloonHong KongChina State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 101408China State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical UniversityXi’an 710072China Unit of Structures Department of Materials Science and EngineeringKTHStockholm SE-10044Sweden Thermo-Calc Software Råsundav.18SolnaSE-16767Sweden Department of Materials Science and Engineering College of EngineeringCity University of Hong KongKowloon TongKowloonHong KongChina Institute of Advanced Wear&Corrosion Resistant and Functional Materials Jinan UniversityGuangzhou 510632China Department of Advanced Design and System Engineering College of EngineeringCity University of Hong KongKowloon TongKowloonHong KongChina

High corrosion resistance of alloys is essential for their structural applications;however,most alloys suffer from degradation of their corrosion resistance with the increasing acidity of their ***,we developed a series of medium-entropy alloys(MEAs)in this work,which ex-hibit high strength,superior fracture toughness and ultra-high corrosion resistance,outperforming the variety of corrosion resistant alloys hitherto *** interestingly,our MEAs exhibit an unusual anti-corrosion behavior and their corrosion resistance increases with acidity in Cl−containing *** extensive thermodynamic calculations,density functional theory(DFT)simulations and experi-ments,we reveal that the unusual anti-corrosion behavior of our MEAs can be attributed to their surface chemical complexity,which facilitates the physio-chemical-absorption of H_(2)O and O_(2)and thus the rapid formation of metastable medium entropy passive films that contain the lowest amount of defects,as compared to the passive films on conventional alloys reported in the literature.

关键词： Corrosion Passivation Alloy design Multi-principal element alloys Medium-entropy alloys

MODELING OF STATIC RECRySTALLIZATION KINETICS OF Nb-BEARING STEELS

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Acta Metallurgica Sinica(English Letters) 2006年第4期19卷 271-278页

作者： L.q. Ma Z.y. Liu S.H. Jiao X.q. yuan D. Wu The State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110004 China Institute of Research and Development Baosteel Co. Ltd Shanghai 201900 China

By using isothermal double hit compression tests and applying the 2% offset method, a new model was developed to predict the microstructural evolution of Nb-bearing steels at temperatures above and below the start temperature of strain-induced precipitation （Tp）. The Tp was developed as a function of true strain, initial austenite grain size and the Nb content. The activation energy of static recrystallization （qrex） was expressed as a function of the content of different alloy elements. It was found that Nb played the most important role in increasing the value of qrex, The microstructural observations and measurements confirmed the validity of the model developed in the present investigation.

关键词： Nb-bearing steel static recrystallization Tp (start temperature of strain-induced precipitation) activation energy

INFLUENCE OF SURFACE-ACTIVE ELEMENTS ON FLUID FLOW OF MIG WELDPOOL

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Acta Metallurgica Sinica(English Letters) 2004年第2期17卷 189-193页

作者： J.S.Sun J.q.Gao y.Feng y.W.Luan MOEKeyLab.ofLiquidStructureandheredityofMaterials ShandongUniversityJi＇nan250061China TechnologyCenter Ji＇nanIronandSteelGroupJi＇nan250101China

A mathematical model describing the behavior of metal inert gas (MIG) welding isformulated in the paper. By means of numerical simulation, the influence of surface-active elements on fluid flow of MIG weldpool is studied. The calculation resultsshow that by adding surface-active elements, the fluid flow behavior is drasticallychanged and the flow fluid flows from lower to upper in vertical direction at the rearof weldpool (w>0). The physical phenomenon is explained from the viewpoint of fluidflow behavior of weldpool that the properties of weld metal is greatly improved andthe content of diffused hydrogen is reduced, thus providing a basis for developing newwelding materials.

关键词： surface-active elements fluid flow numerical analysis

Magnetism,optical,and thermoelectric response of CdFe_2O_4by using DFT scheme

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Chinese Physics B 2018年第3期27卷 376-383页

作者： q Mahmood M yaseen K C Bhamu Asif Mahmood y Javed Shahid M Ramay Materials Growth and Simulation Laboratory Department of PhysicsUniversity of the Punjab Department of Physics University of AgricultureFaisalabad Department of Physics Goa University Chemical Engineering Department College of Engineering King Saud University Physics and Astronomy Department College of Science King Saud University

Comparative analysis of electronic, magnetic, optical, and thermoelectric properties of CdFe2O4, calculated by em- ploying PBEsol ＋ mBJ has been done. The PBEsol reveals metallic nature, while TB-mBJ illustrates ferromagnetic semiconducting behavior. The reasons behind the origin of ferromagnetism are explored by observing the exchange, crystal field, and John-Teller energies. The optical nature is investigated by analyzing dielectric constants, refraction, absorption coefficient, reflectivity, and optical conductivity. Finally, thermoelectric properties are elaborated by describing the electri- cal and thermal conductivities, Seebeck coefficient, and power factor. The strong absorption for the visible energy and high power factor suggest CdFe2O4 as the potential candidate for renewable energy applications.

关键词： frustrated magnetism density functional theory John-Teller distortion Hund's rule

MICROSTRUCTURAL STUDy OF Fe-Cr-Al/Al COMPOSITE COATINGS DURING OXIDATION AND SULFIDATION AT 900℃

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Acta Metallurgica Sinica(English Letters) 2007年第2期20卷 87-94页

作者： Z.L. Zhang D.y. Li X.q. Dong School of Material Science and Engineering Shenyang University of Technology Shenyang 110023 China

The microstructure of a composite coating system, which was composed of an inner layer of Fe-Cr-Al and an outer layer of aluminum, was studied after it was respectively oxidized and sulfurdized at elevated temperatures. Apart from the Al2O3 scale formed on the surface, the microstructure of the composite coatings exposed at 900℃ in air for 4h was a three-layer structure. The first layer consisted of a solid solution of Cr and Fe in α aluminum and an intermetallic compound FeAl3 while the second layer was a single phase of the aluminide and the third layer still remained the same appearance as the original Fe-Cr-Al coating. The microstructural observation of the specimen tested at 850-900℃ at low oxygen pressure and high sulfur pressure for 576h revealed that the surface coatings of the specimen had transformed into a duplex structure containing an outer layer and a thicker aluminide layer beneath. X-ray diffraction results showed that the out layer was composed of Al2S3 and Al2O3 and that AlCrFee was the main phase composition of the aluminide layer, with a few of Al2S3 and Al2O3 accompanied.

关键词： arc spray Fe-Cr-Al composite coating microstructure

Effect of Ni Content on Mechanical Properties and Corrosion Behavior of Al/Sn－9Zn－xNi/Cu Joints

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Journal of Materials Science & Technology 2012年第9期28卷 844-852页

作者： M.L.Huang N.Kang q.Zhou y.Z.Huang Key Laboratory of Liaoning Advanced Welding and Joining Technology School of Materials Science&EngineeringDMian University of TechnologyDalian 116024China

The effects of Ni content on the microstructure and the wetting behavior of Sn-9Zn-xNi solders on Al and Cu substrates, as well as the mechanical properties and electrochemical corrosion behavior of Al/Sn-9Zn-xNi/Cu solder joints, were investigated. The microstructure of Sn-gZn-xNi revealed that tiny Zn and coarsened Ni5Zn21 phases dispersed in theβ-Sn matrix. The wettability of Sn-9Zn-xNi solders on Al substrate was much better than that on Cu substrate. With increasing Ni content, the wettability on Cu substrate was slightly improved but became worse on Al substrate. In the Al/Sn-9Zn-xNi/Cu joints, an Al4.2Cu3.2Zn0.7 intermetallic compound （IMC） layer formed at the Sn-gZn-xNi/Cu interfaces, while an Al-Zn-Sn solid solution layer formed at the Sn-9Zn-xNi/Al interface. The mixed compounds of Ni3Sna and Al3Ni dispersed in the solder matrix and coarsened with increasing Ni content, thus leading to a reduction in shear strength of the Al/Sn-9Zn- xNi/Cu joints. Al particles were segregated at both interfaces in the solder joints. The corrosion potentials of Sn-9Zn-xNi solders continuously increased with increasing Ni content. The Al/Sn-9Zn-0.25Ni/Cu joint was found to have the best electrochemical corrosion resistance in 5% NaCl solution.

关键词： Al-Cu disslmilar-metal solder joint Sn-9Zn-xNi Microstructure Mechanicalproperties Electrochemical corrosion Corrosion potential