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Microstructural Analysis of Ultrasonic Welded AA6061 by Electron backscattered Diffraction

稀有金属材料与工程 2009年第A3期38卷 147-151页

作者： zhu z Wynne b P Ghassemieh E Siddiq A Nanchang University Nanchang 330031 China University of Sheffield Sheffield S1 3JD UK IMMPETUS Institute for Microstructural and Mechanical Process Engineering University of Sheffield Sheffield S 1 3JD UK

Ultrasonic welding can be used to join plastic and metal through high-frequency (more than 20 kHz) acoustic vibrations. Aluminium alloy is widely used in electronics, automotive and aerospace. The mechanical vibrations used during ultrasonic metal welding are introduced horizontally. During ultrasonic metal welding, a complex process is triggered involving static forces, oscillating shearing forces and a moderate temperature increase in the welding area. As the energy is introduced to the weld zone, there are three important phenomena occurring which are surface effect, volume effect and thermal effect. As it is known, microstructure is directly linked to the mechanical properties including fatigue resistance, fatigue life and fracture strength. So the microstructure analysis is important to evaluate the ultrasonically welded aluminium alloy’s properties. Also, mechanical properties of metal sheets, such as plastic anisotropy and formability, can be improved by a proper crystallographic texture control. That means the texture has great influence on the plastic anisotropy of the final recrystallized sheets. Optical microscopy (OM) can be used for showing the grain size and grain shape. However, to examine the relationship between mechanical behaviour and microstructure of the weldment, optical microscopy(OM) is not sufficient. OM cannot delineate a grain structure in the weld zone. The etched surface exhibited granularity at the micron level, but it was not clear if that reflected the grain structure. Electron backscatter diffraction (EbSD) in an SEM has become the most widely used technique for determination of microtexture. In this research, high-resolution electron backscatter diffraction is used to study the effects of the vibration on the evolution of microstructure in AA6061. The orientation image maps (OIM), polar figures (PF), and orientation distribution functions (ODF) of the samples are obtained. The characteristics of the crystallographic orientation, the

关键词：超声波焊接塑料复合材料抗疲劳强度

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Effect of Geometrical Structure on Transport Properties of Silicene Nanoconstrictions

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Chinese Physics Letters 2021年第12期38卷 57-61页

作者： Yawen guo Wenqi Jiang Xinru Wang Fei Wan Guanqing Wang G.H.zhou z.b.Siu Mansoor b.A.Jalil Yuan Li Department of Physics Hangzhou Dianzi UniversityHangzhou 310018China Department of Physics and Key Laboratory for Low-Dimensional Quantum Structures and Manipulation(Ministry of Education) Hunan Normal UniversityChangsha 410081China Computational Nanoelectronics and Nano-device Laboratory Electrical and Computer Engineering DepartmentNational University of SingaporeSingapore 117576Singapore

We study electrical modulation of transport properties of silicene nanoconstrictions with different geometrical *** investigate the effects of the position and width of the central scattering region on the conductance with increasing Fermi *** is found that the conductance significantly depends on the position and the width of the ***,the symmetrical structure of the central constriction region can induce a resonance effect and significantly increase the system’s *** also propose a novel two-channel structure with an excellent performance on the conductance compared to the one-channel structure with the same total *** geometrically-induced conductance modulation of silicene nanostructures can be achieved in practice via current nanofabrication technology.

关键词： energy conductance structure

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A comparative study on microstructure,nanomechanical and corrosion behaviors of AlCoCuFeNi high entropy alloys fabricated by selective laser melting and laser metal deposition

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Journal of Materials Science & Technology 2022年第36期131卷 221-230页

作者： Yaojia Ren Hong Wu bin Liu Yong Liu Sheng guo zbJiao Ian baker State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Department of Industrial and Materials Science Chalmers University of TechnologyGothenburg SE-41296Sweden Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHong Kong 999077China Thayer School of Engineering Dartmouth CollegeHanover NH 03755-8000United States

The present study investigated the microstructure,nanomechanics,and corrosion behavior of AlCoCuFeNi high entropy alloys fabricated by selective laser melting(SLM)and laser metal deposition(LMD).The microstructure of SLM-processed specimens was mainly composed of columnar-grained bCC matrix(^90μm in width)and Cu-rich twinned FCC *** columnar grains grew epitaxially along the building direction and exhibited a strong{001}*** comparison,a coarse columnar-grained bCC matrix(^150μm in width)with a strongertexture,rod-like b2 precipitates,and large core-shell structured FCC phases were formed in the LMD-processed specimens due to the higher heat accumulation ***,the LMD-processed specimens showed a lower hardness,wear resistance,and corrosion resistance,but higher creep resistance and reduced Young's modulus than the SLM-processed *** cracks occurred in both types of specimens,which could not be completely suppressed due to Cu segregation.

关键词： Selective laser melting Laser metal deposition High entropy alloys Nanomechanics Corrosion

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CREEP bEHAVIOR MODELING OF UDIMET 720Li SUPERALLOY

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Acta Metallurgica Sinica(English Letters) 2005年第1期18卷 65-73页

作者： V.Lupinc M.Maldini L.z.zhou J.T.guo Isfitutoperl＇EnergedcaeperleInterfasi ConsigfioNazionaledelleRicercheCNR-IENI20125MilanItaly Isfitutoperl＇EnergedcaeperleInterfasi ConsigfioNazionaledelleRicercheCNR-IENI20125MilanItaly／／InstituteofMetalResearchTheChineseAcademyofSciencesShenyang110016China InstituteofMetalResearch TheChineseAcademyofSciencesShenyang110016China

Constant load creep tests on isothermally forged Udimet 720Li, an advanced superalloy for gas turbine disc application, were run in the stress/temperature field 900-450MPa/650-700 ℃ producing rupture times in the 20-5000h range. The creep curves have shown a predominant accelerating creep stage, that has been described by the following equation: where ε min depends on stress and temperature, while parameter C depends mainly on stress. A strain dependent damage, defined by the parameter C, causes the accelerating creep stage at stresses lower than 750MPa, whilst its contribution to the creep strain acceleration is less important at higher stresses. The model rationalizes the different behaviors at high and low stress and has been validated with variable stress and temperature creep behavior.

关键词： Udimet 720Li creep creep curve shape creep damage

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Effect of Al_(2)O_(3)on the Mechanical Properties of(b_(4)C+Al_(2)O_(3))/Al Neutron Absorbing Materials

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Acta Metallurgica Sinica(English Letters) 2024年第8期37卷 1411-1420页

作者： J.X.Cai b.M.Shi N.Li Y.Liu z.G.zhang Y.N.zan Q.z.Wang b.L.Xiao z.Y.Ma Shi‑Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Nuclear Equipment Division Beijing Institute of Nuclear EngineeringChina Nuclear Power Engineering Co.Ltd.Beijing 100840China Department of Materials Science School of Mechanical EngineeringShenyang UniversityShenyang 110044China

b_(4)C/Al composites are widely utilized as neutron absorbing materials for the storage and transportation of spent nuclear *** order to improve the high-temperature mechanical properties of b_(4)C/Al composites,in-situ nano-Al_(2)O_(3)was introduced utilizing oxide on Al powder *** this study,the Al_(2)O_(3)content was adjusted by utilizing spheroid Al powder with varying diameters,thereby investigating the impact of Al_(2)O_(3)content on the tensile properties of(b_(4)C+Al_(2)O_(3))/Al *** was found that the pinning effect of Al_(2)O_(3)on the grain boundaries could hinder the recovery of dislocations and lead to dislocation accumulation at high *** the result,with the increase in Al_(2)O_(3)content and the decrease in grain size,the high-temperature strength of the composites increased *** finest Al powder used in this investigation had a diameter of 1.4μm,whereas the resultant composite exhibited a maximum strength of 251 MPa at room temperature and 133 MPa at 350℃,surpassing that of traditional b_(4)C/Al composites.

关键词： Al matrix composites Neutron absorbing materials (b_(4)C+Al_(2)O_(3))/Al composites High-temperature strength

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An Investigation of Ionic Flows in a Sphere-Plate Electrode Gap

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Plasma Science and Technology 2013年第10期15卷 1012-1019页

作者： H.z.ALISOY S.ALAGOz G.T.ALISOY b.b.ALAGOz Department of Electrical-Electronics Inonu University Department of Physics Inonu University Department of Mathematics Inonu University

This paper presents analyses of ion flow characteristics and ion discharge pulses in a sphere-ground plate electrode system. As a result of variation in electric field intensity in the electrode gap, the ion flows towards electrodes generate non-uniform discharging pulses. Inspection of these pulses provides useful information on ionic stream kinetics, the effective thickness of ion cover around electrodes, and the timing of ion clouds discharge pulse sequences. A finite difference time domain （FDTD） based space-charge motion simulation is used for the numerical analysis of the spatio-temporal development of ionic flows following the first Townsend avalanche, and the simulation results demonstrate expansion of the positive ion flow and compression of the negative ion flow, which results in non-uniform discharge pulse characteristics.

关键词： ion flow FDTD simulation space charge motion

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Antimonene-based saturable absorber for a soliton mode-locked and Q-switched fiber laser in the 2 μm wavelength region

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Chinese Physics b 2023年第6期32卷 259-269页

作者： H Ahmad b Nizamani M z Samion N Yusoff M F Ismail Photonics Research Centre Universiti Malaya50603 Kuala LumpurMalaysia Physics Department Faculty of ScienceUniversiti Malaya50603 Kuala LumpurMalaysia Distinguished Visiting Professor Universiti Kuala Lumpur British Malaysian Institute(UniKL BMI)Batu 8Jln Sungai Pusu53100SelangorMalaysia

We demonstrate antimonene as a saturable absorber(SA) to generate an ultrafast mode-locked and Q-switched laser in the 2 μm wavelength region. The two antimonene-based SAs were prepared and inserted separately in a thulium–holmiumdoped fiber laser to produce the pulsed laser. Antimonene was coated onto a tapered fiber to generate soliton mode-locked pulses and used in thin-film form for the generation of Q-switched pulses. The mode-locking was stable within a pump power of 267 m W–511 m W, and the laser operated at a central wavelength of 1897.4 nm. The mode-locked laser had a pulse width of 1.3 ps and a repetition rate of 12.6 MHz, with a signal-to-noise ratio of 64 d b. Q-switched laser operation was stable at a wavelength of 1890.1 nm within a pump power of 312 m W–381 m W. With the increase in pump power from 312 m W to 381 m W, the repetition rate increased to a maximum of 56.63 k Hz and the pulse width decreased to a minimum value of 2.85 μs. Wide-range tunability of the Q-switched laser was also realized within the wavelength range of1882 nm–1936 nm.

关键词： mode-locking Q-switched fiber laser optical saturable absorber

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Synthesis,characterization and application of PVA/ionic liquid mixed matrix membranes for pervaporation dehydration of isopropanol

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Chinese Journal of Chemical Engineering 2017年第10期25卷 1402-1411页

作者： Ganesh b.Thorat Smita Gupta z.V.P.Murthy Department of Chemical Engineering Sardar Vallabhbhai National Institute of Technology Surat 395007 Gujarat India

In this study,polyvinyl alcohol(PVA)–ionic liquid(IL) membranes were prepared for the separation of isopropyl alcohol(IPA)–water azeotropic mixtures by ***-IL composite membranes were prepared by simple solvent evaporation method using four ILs,viz.,1-n-butyl-3-methylimidazolium chloride(bMIMCl),1-hexyl-3-methylimidazolium chloride(HMIMCl),1-hexyl-3-methylimidazolium tetra fluoroborate(HMIMbF4) and 1-octyl-3-methylimidazolium chloride(OMIMCl).Three ILs were used to study the effect of alkyl chain on the pervaporation *** study had focused on the effect feed water concentration from 10%–40%and effect of feed temperature from 50–80°*** properties of all the membranes were studied using Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM) and contact angle *** Arrhenius activation energies for permeation were estimated to be in the range 4–12 kJ·mol-1 from the temperature dependent permeation values.

关键词： Composite membranes Ionic liquids Dehydration Isopropanol Pervaporation

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Efect of Nanometer WC Coating on Thermal Conductivity of Diamond/6061 Composites

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Acta Metallurgica Sinica(English Letters) 2023年第1期36卷 118-126页

作者： z.Y.Dong D.Wang W.G.Wang b.L.Xiao z.Y.Ma Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Liaoning Shihua University Fushun 113001China

Diamond has poor interface tolerance with *** enhance interface bonding,in this study,tungsten carbide(WC)nanocoatings on the surface of diamond particles were prepared using sol–gel and in-situ reaction ***_(3) sol–gel with two concentrations,0.2 mol/L,and 0.5 mol/L,was,respectively,coated on diamond particles,then sintered at 1250℃for 2 h to produce WC *** concentration of 0.2 mol/L WO_(3) sol–gel was not enough to cover the surface of the diamond completely,while 0.5 mol/L WO_(3) sol–gel could fully cover ***,WO_(3) was preferentially deposited on{100}planes of the ***_(3) converted to WC in-situ nanocoatings after sintering due to the in-situ reaction of WO_(3) and *** diamond-reinforced Al composites with and without WC coating were fabricated by powder *** diamond/Al composite without coating has a thermal conductivity of 584.7 W/mK,while the composite with a coating formed by 0.2 mol/L and 0.5 mol/L WO_(3) sol–gel showed thermal conductivities of 626.1 W/mK and 584.2 W/mK,*** moderate thickness of nanocoatings formed by 0.2 mol/L WO_(3) sol–gel could enhance interface bonding,therefore improving thermal *** nanocoating produced by 0.5 mol/L WO_(3) sol–gel cracked during the fabrication of the composite,leading to Al12W formation and a decrease in thermal conductivity.

关键词： Diamond Al matrix composite Nanometer coating WC Thermal conductivity

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An explicit solution to a three-dimensional wedge problem considering two edges effect

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Friction 2020年第2期8卷 370-383页

作者： L.guo z.M.zHANG W.WANG Y.zHAO P.L.WONG School of Mechatronic Engineering and Automation Shanghai UniversityShanghai 200444China Department of Mechanical Engineering City University of Hong KongHong Kong SARChina

The paper presents an explicit matrix algorithm to solve the problem of an elastic wedge with three loaded *** algorithm makes use of a recently published concept of transformation matrix,by which the original surface loads are converted to equivalent loads in *** three loaded edges are considered *** developed algorithm is used to study the effects of two free edges of a steel block and tapered rollers with different contact *** two load-free edges can substantially increase deformation if the two edges are close in *** results of the tapered roller simulation show that deformation is considerably sensitive to the contact angle of the tapered *** largest deformation appears at the big end of the ***,empirical formulae for correction factors for the calculation of block or quarter-space deformation based on half-space solutions are summarized.

关键词： contact mechanics two edge surfaces finite line contact tapered roller contact

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