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Nano-phase transformation of composite precipitates in multicomponent Al-Mg-Si(-Sc)alloys

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Journal of Materials Science & Technology 2022年第15期110卷 216-226页

作者： S.b.Wang c.F.Pan b.Wei X.Zheng y.X.Lai J.H.chen Key Laboratory of LcR Materials and Devices of yunnan Province National Center for International Research on Photoelectric and Energy MaterialsSchool of Materials and EnergyYunnan UniversityKunming 650091China collaborative Innovation center of Renewable Energy Materials and Department of Physics Guangxi UniversityNanning 530004China center for High-Resolution Electron Microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

Sc-addition can significantly enhance the performance of the micro-alloyed Al-Mg-Si-Sc ***,the mechanisms by which the Sc element modifies the microstructure of the alloys are still unknown in many ***,using atomic-scale transmission electron microscopy and atomic-resolution spectroscopy,we have revealed the microstructural differences between two age-hardened Al-0.5Mg-0.4Si(wt.%)alloys with and without *** first significant effect of Sc-addition on the precipitation microstructure of the Al-Mg-Si-Sc alloy is that Sc-atoms may distribute at theβ"-precipitate/Al-matrix interface and therefore accelerate aging kinetics at the initial stage of *** second significant effect of Sc-addition is that in the transition from theβ"-hardened peak-age stage to theβ′-hardened late stage,Sc-atoms can greatly improve the stability of transitionalβ"/b'/β′composite precipitates by entering the b'-substructures and/or locating at the precipitate/Al *** such Sc-atoms effectively suppressβ"toβ'transformation and cross-sectional coarsening of bothβ"and composite precipitates,leading to much finer precipitate needles with smaller diameter but much larger length,as compared with those precipitate needles formed in the alloy without ***,the alloy with Sc-addition exhibits a much better thermal stability than that without Sc.

关键词： Al alloy Strengthening mechanism Phase transition Transmission electron microscopy

Design Features and commissioning of the Versatile Experiment Spherical Torus (VEST) at Seoul National University

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Plasma Science and Technology 2013年第3期15卷 244-251页

作者： K.J.cHUNG y.H.AN b.K.JUNG H.y.LEE c.SUNG y.S.NA T.S.HAHM y.S.HWANG Department of Nuclear Engineering Seoul National University

A new spherical torus called VEST （Versatile Experiment Spherical Torus） is designed, constructed and successfully commissioned at Seoul National University. A unique design feature of the VEST is two partial solenoid coils installed at both vertical ends of a center stack, which can provide sufficient magnetic fluxes to initiate tokamak plasmas while keeping a low aspect ratio configuration in the central region. According to initial double null merging start-up scenario using the partial solenoid coils, apprdpriate p6wer supplies for driving a toroidal field coil, outer poloidal field coils, and the partial solenoid coils are fabricated and successfully commissioned. For reliable start-up, a pre-ionization system with two cost-effective homemade magnetron power supplies is also prepared. In addition, magnetic and spectroscopic diagnostics with appropriate data acquisition and control systems are well prepared for initial operation of the device. The VEST is ready for tokamak plasma operation by completing and commissioning most of the designed components.

关键词： spherical torus partial solenoids double null merging start-up

Achieving a strong polypropylene/aluminum alloy friction spot joint via a surface laser processing pretreatment

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Journal of Materials Science & Technology 2020年第15期47卷 103-114页

作者： S.c.Han L.H.Wu c.y.Jiang N.Li c.L.Jia P.Xue H.Zhang H.b.Zhao D.R.Ni b.L.Xiao Z.y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang110016China Department of Materials Science and Engineering Guilin University of TechnologyGuilin541006China

Strong metal/non-polar plastic dissimilar joints are highly demanded for the lightweight design in many fields,which,however,are rather challenging to achieve directly via *** this study,we designed a laser processing pretreatment on the Al alloy to create a deep porous Al surface structure,which was successfully joined to the polypropylene(PP) via friction spot welding.A maximum joint strength of29 MPa was achieved,the same as that of the base PP(*** joint efficiency reached 100%),much larger than ever *** joining mechanism of the Al alloy and the PP was mainly attributed to the large mechanical interlocking effect between the laser processed Al porous structure and the re-solidified PP and the formation of chemical bond at the *** deep porous Al surface structure modified by laser processing largely changed the Al-PP reaction *** evidence of the c-O-Al chemical bond was first time found at the non-polar plastic/Al joint interface,which was the reaction result between the oxide on the Al alloy surface and thermal oxidization products of the PP during *** study provides a new way for enhancing metal-plastic joints via surface laser treatment techniques.

关键词： Friction stir welding Hybrid joint Metal Polymer Surface treatment Interface

Modelling of sediment movement in the surf and swash zones

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Acta Oceanologica Sinica 2015年第2期34卷 137-142页

作者： TOKPOHOZIN N.b. KOUNOUHEWA b. AVOSSEVOU G.y.H. HOUEKPOHEHAM A. AWANOU c.N. Institut de Mathématiques et de Sciences Physiques (IMSP/UAc) centre béninois de la Recherche Scientifique et Technique (cbRST) Laboratoire de Physique du Rayonnement (LPR/FAST-UAc)

Under the action of marine currents,non-cohesive sediments evolve by bed-load,by saltation or suspension depending on their *** authors have considered that the movement of sediment is bidimensional and modelized the effects of swell by a constant velocitynear the *** we have studied the velocity profile of fluctuating currents near the seabed and studied the movement of sediment in *** results show that in the areas of study（surf and swash）the movement of sediment occurs in a volume,and the evolution of sediment varies from an areato *** obtained theoretical profiles of the position and velocity vectors confirm the observations of several authors.

关键词： non-cohesive sediments sediment dynamics swell trajectory of sediment velocity drive

First-principles Study of Point Defects in Stoichiometric and Non-stoichiometric y_4Al_2O_9

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Journal of Materials Science & Technology 2013年第12期29卷 1161-1165页

作者： Z.Li b.Liu J.M.Wang L.c.Sun J.y.Wang y.c.Zhou Z.J.Hu High-performance ceramics Division Shenyang National Laboratory for Materials ScienceInstitute of Metal ResearchChinese Academy of Sciences Aerospace Research Institute of Materials and Processing Technology

by using the first-principles calculation, we studied the mechanisms of point defects in y4AI209 （yAM）, a promising ternary oxide with excellent optical and thermal properties. It is found that the predominant native defect species is closely dependent on the chemical potentials of each constituent. In the case of O-rich condition, the oxygen interstitial has the very low defect formation energy, followed by the anti-site defects and AI vacancy; in the case of AI-rich condition, the oxygen vacancy yields the lowest defect formation energy, followed by the anti-site defects and AI interstitial. The present result shows that in all the possible chemical potential ranges, anti-site defects have relatively low defect formation energy and might exist in high concentration in yAM. Furthermore, AIy anti-site has relatively lower defect formation energy than the yAt anti- site throughout. The behaviors of defect complexes under non-stoichiometric condition, such as the AI203 or y203 excess, are also investigated. The results provide helpful guide to optimize the experimental synthesizing of yAM.

关键词： Ternary y-AI-O oxide Defect formation energy chemical potential

Optimum calibration of a parallel kinematic manipulator using digital indicators

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Advances in Manufacturing 2014年第3期2卷 222-230页

作者： V.b.Saputra S.K.Ong A.y.c.Nee Department of Mechanical Engineering Faculty of EngineeringNational University of SingaporeSingapore 117576Singapore

This paper presents a calibration method for parallel manipulators using a measurement system specially installed on an external fixed frame. The external fixed frame is important as an error reference for calibration in certain operations, such as in the configuration of a parallel manip- ulator functioning as a machine tool where the workpiece is fixed to a worktable. The pose of the end-effector is mea- sured using three digital indicators installed on the external fixed frame. To enable measurement, the end-effector is assumed to be a plane large enough that all digital indicators could touch. The error is defined as the difference between the theoretical and actual readings of the digital indicators. The geometric parameters of the parallel manipulator are optimized to minimize this error. This calibration method is low cost and feasible for compensating geometric parameter errors for a parallel manipulator. Optimal pose selection for the calibration is achieved using a swarm intelligence search algorithm. The method is implemented on a prototype of a six degrees-of-freedom （DOFs） Gough-Stewart platform constructed to function as a machine tool.

关键词： calibration Parallel kinematic manipulator(PKM) Digital indicator

constitutive equation and model validation for a 31 vol.% b_4cp/6061Al composite during hot compression

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Journal of Materials Science & Technology 2018年第10期34卷 1730-1738页

作者： L. Zhou c. cui Q.Z. Wang c. Li b.L. Xiao Z.y. Ma Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Electromechanical and Vehicle Engineering Yantai University Yantai 264005 China School of Mechanical Engineering Shenyang Ligong University Shenyang 110159 China Nuclear and Radiation Safety center Ministry of Environmental Protection Beijing 100082 China

An accurate constitutive equation is essential to understanding the flow behavior of b4c/A1 compos-ites during the hot deformation. However, the constitutive equations developed previously in literature are generally for low strain rate deformation. In the present work, we modified the general consti-tutive equation and take the high strain rate correction into account. The constitutive equation for a 31 vol.% b4cp/6061AI composite was constructed based on the flow stresses measured during isothermal hot compression at temperatures ranging from 375 to 525 ℃ and strain rates from 0.01 to 10 s^-1. The experimental flow stresses were corrected by considering temperature-dependent Arrhenius factor. The modified equation was then verified by using DEFORM-3D finite element analysis to simulate the exper-imental hot compression process. The results show that the modified equation successfully predicts flow stress, load-displacement, and the temperature rise. This helps to optimize the hot deformation process, and to obtain desirable properties, such as reduced porosity and homogenous particle distribution in b4c/AI composites.

关键词： composites b4c/AI constitutive equation Hot compression Finite element simulation

Diffusion of Hydrogen in Amorphous NicrFeSib Alloy

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Journal of Materials Science & Technology 1996年第1期12卷 15-18页

作者： Zuo, y yang, b Xu, RS Dept. of Applied chemistry Beijing University of Chemical Technology Beijing 100029 China

The diffusion of hydrogen in amorphous NicrFeSib alloy has been studied by electrochemical method. In the temperature range of 20 similar to 50 degrees c, diffusion coefficient of hydrogen in the alloy follows the equation: D(cm(2)/s) = 9.27x10(-8) exp(-53.4 kJ/RT). At room temperature the diffusion coefficient D and the solubility c-0 are 6.125 x 10(-12) cm(2)/s and 0.007 mol/cm(3), respectively. When As2O3 is added into the cathodic solution or the charging current density is increased, the diffusion coefficient and solubility increase, and the diffusion activation energy decreases. The influence of amorphous structure on diffusion and solution of hydrogen is discussed.

关键词： Nickel alloys

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