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Hard yet tough and self-lubricating(cuNiTiNbcr)c_(x) high-entropy nanocomposite films:Effects of carbon content on structure and properties

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Journal of Materials Science & Technology 2024年第6期173卷 20-30页

作者： Y.T.Li x.M.chen x.K.Zeng M.Liu x.Jiang Y.x.Leng Key Laboratory of Advanced Technologies of Materials Ministry of EducationSchool of Materials Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China Key Laboratory of Noise and Vibration Research Institute of AcousticsChinese Academy of SciencesBeijing 100190China State Key Laboratory of Acoustics Institute of AcousticsChinese Academy of SciencesBeijing 100190China School of Mechanical and Electrical Engineering Mianyang Teachers’CollegeMianyang 621000China

The single-phase high-entropy alloy film is difficult to meet severe friction conditions due to its low hardness and high friction ***-composite structure film is composed of at least two separated phases,showing the properties of strength and toughness integration and excellent wear *** design of nanocomposite structures can effectively improve the mechanical properties and tribological properties of high-entropy alloy *** this study,the(cuNiTiNbcr)c_(x) nanocomposite high-entropy films(heFs)integrated with high hardness,high toughness,and self-lubrication were synthesized by the double-target co-sputtering *** effect of carbon content on microstructure,mechanical properties,and tribological properties of(cuNiTiNbcr)c_(x) films was *** the increase of carbon content in the heFs,the carbon atoms preferentially react with Ti,Nb,and cr to form a(TiNbcr)c ceramic-reinforced phase,and then the excess carbon atoms precipitate in the form of amorphous carbon(a-c)lubricating phase in the *** structure of the heFs changes from an amorphous structure to a nanocomposite structure of amorphous(amorphous cuNiTiNbcr phase+a-c phase)/nanocrystalline(TiN-bcr)c *** the carbon content is about 21.2 at.%,the carbide phase in the film reaches saturation and the hardness and modulus of the films are highest,which are 18 GPa and 228 GPa,*** heFs with a carbon content of 44.0 at.%show the best toughness and tribological properties with a friction coefficient of 0.16 and a wear rate of 2.4×10^(-6) mm^(3)/(N m),which is mainly attributed to the excellent resistance to fatigue crack growth and the interfacial lubricating layer formed in the friction *** nanocomposite(cuNiTiNbcr)c_(x) heFs show very promising application prospect in the field of friction protection.

关键词： High-entropy films Nanocomposite Double-target co-sputtering Strengthening-toughening Tribological properties

Non-contact evaluation of the resonant frequency of a microstructure using ultrasonic wave

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Acta Mechanica Sinica 2010年第2期26卷 317-323页

作者： x. Kang x. Y. he c.J. Tay c. Quan Department of Applied Mechanics Nanjing University of Science and Technology 210094 Nanjing China Institute of Engineering Mechanics Southeast University210096 Nanjing China Department of Mechanical Engineering National Universityof Singapore 9 Engineering Drive 1 117576 Singapore Singapore

This paper presents a novel non-contact method for evaluating the resonant frequency of a microstructure, Firstly, the microstructure under test is excited by ultrasonic waves. This excitation method does not impose any undefined load on the specimen like the electrostatic excitation and also this is the first actual use of ultrasonic wave for exciting a microstructure in the literature. Secondly, the amplitudes of the microstructure are determined by image edge detection using a Mexican hat wavelet transform on the vibrating images of the microstructure. The vibrating images are captured by a ccD camera when the microstructure is vibrated by ultrasonic waves at a series of discrete high frequencies （〉30 kHz）. Upon processing the vibrating images, the amplitudes at various excitation frequencies are obtained and an amplitude-frequency spectrum is obtained from which the resonant frequency is subsequently evaluated. A micro silicon structure consisting of a perforated plate （192 × 192 μm） and two cantilever beams （76 × 43 μm） which is about 4 μm thickness is tested. Since laser interferometry is not required, thermal effects on a test object can be avoided. hence, the setup is relatively simple. Results show that the proposed method is a simple and effective approach for evaluating the dynamic characteristics of microstructures.

关键词： Non-contact Microstructure· Resonant frequency Ultrasonic wave Image processing

Phase-field modeling for anisotropic ductile damage of magnesium alloys at finite deformations

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Journal of Magnesium and Alloys 2024年第7期12卷 2967-2984页

作者： c.xie x.K.he x.Liu J.H.Ye J.B.chen Faculty of Mechanical Engineering and Mechanics Ningbo UniversityNingbo 315211PR China Key Laboratory of High Temperature Wear Resistant Materials Preparation Technology of Hunan Province Hunan University of Science and TechnologyXiangtan 411201PR China

The damage anisotropy of an extruded ZK60 Mg alloy is characterized using tensile tests and scanning electronic *** accumulation of anisotropic deformations leads to the great differences of the dimple evolution and strains at fracture along different loading *** introduce the anisotropic deformation information into the damage constitutive relationship,a thermodynamically consistent phase-field model of ductile damage fully coupled with elastoplastic finite deformations is developed in this *** the user-defined constitutive relationship and displacement-temperature coupling element,the finite element simulations are *** results show that:(1)ZK60 Mg alloys presents clear R-value difference in 0°,45°,and 90°tests of intact *** 45°test possesses the greatest R-value(1.50)and the greatest strain at fracture,however,the R-value for 0°is less than 1,indicating the thinning is preferential.(2)The higher ultimate stress leads to a larger average dimension of the dimples,whereas the higher density correlates with a larger elongation ratio at the *** disappearance of the stress-bearing area indicates that the phase-field assumption on stress degradation is completely compatible with the dimple analysis on fractography.(3)The simulation results of the stress-strain relationships and damage paths correlate well with the experimental ductile damage of magnesium alloys at 200◦*** errors are basically attributed to the modeling parameters and finite element iteration *** proposed model presents fine applicability and reliability for the predictions of plastic deformations,ductile damage,and fracture of anisotropic Mg alloys.

关键词： Ductile damage Anisotropy Phase field constitutive relationship Magnesium

Distinct Electrical and Mechanical Responses of a cu-10Fe composite Prepared by Hot-Pressed Sintering and Post Treatment

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Acta Metallurgica Sinica(English Letters) 2024年第2期37卷 255-265页

作者： x.Y.Yue S.Y.Peng x.Zhang c.N.he Y.Z.Tian Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Materials Science and EngineeringNortheastern UniversityShenyang110819China School of Materials Science and Engineering and Tianjin Key Laboratory of composite and Functional Materials Tianjin UniversityTianjin300350China Research centre for Metallic Wires Northeastern UniversityShenyang110819China

A cu-10wt%Fe composite was prepared through hot-pressed sintering,and the material was subsequently solution *** hot-pressed sintered and solution treated materials were rolled and *** precipitation behavior and performance changes were systematically studied by using scanning electron microscopy and transmission electron *** contrast to the hot-pressed sintered specimen,the solution treatment significantly affects the thermal stability and properties of the cu-10wt%Fe *** cu-10wt%Fe composite was prepared after solid solution,cold rolling and aging at 773 K for 1 h,and it obtained excellent tensile strength of 494 MPa,uniform elongation of 16.3%,electrical conductivity of 51.1%IAcS and softening temperature of 838 *** for the distinct difference in thermal stability and properties between hot-pressed sintered and solution treated specimens were *** findings provide a theoretical basis for designing high-performance cu-based in-situ composites by post treatment.

关键词： cu-Fe composite Hot-pressed sintering Thermal stability Strength Electrical conductivity

A Quantitative Analysis of Mn Segregation at Partitioned Ferrite/Austenite Interface in a Fe-c-Mn-Si Alloy

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Journal of Materials Science & Technology 2009年第3期25卷 383-388页

作者： H. Guo S.W. Yang c.J.Shang x.M. Wang x.L. he Department of Materials Physics and chemistry University of Science and Technology Beijing Beijing 100083 China

Mn segregation at austenite/ferrite interface is studied in a Fe-c-Mn-Si alloy held at 656℃. Mn is partitioned during the growth of ferrite and as a result, a Mn pile-up exists in front of interface on the matrix side. An approach to evaluate Mn segregation quantitatively is developed by combining STEM raster window scanning and simulation of the interaction of the electron beam with the sample to subtract the contribution of Mn pile-up and obtain pure Mn segregation value. The evaluated maximum Mn interfacial segregation is in the order of a half-monolayer.

关键词： Interfacial segregation Phase transformation STEM Beam broadening

Status and prospects for symmetric organic redox flow batteries

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Journal of Energy chemistry 2025年第1期100卷 125-143页

作者： Md Al Raihan c.Adam Dyker Department of chemistry University of New Brunswick

As environmental concerns from fossil fuel consumption intensify, large-scale energy storage becomes imperative for the integration of renewable sources like wind, hydro, and solar with the electrical *** flow batteries, particularly those employing organic molecules, are positioned as a key technology for this purpose. This review explores the growing field of symmetric organic redox flow batteries(ORFBs) within this context. Unlike traditional asymmetric designs based on unique active materials for each electrode, symmetric ORFBs involve a single bipolar species for both electrodes. This review highlights the benefits of a symmetric design, and categorizes five distinct classes of organic bipolar molecules used in both aqueous and non-aqueous solvents. By providing a comprehensive overview of their cell cycling and performance characteristics, the strengths and weaknesses of the diverse categories of bipolar molecules are highlighted for both solvent systems, as are opportunities for future development. This should guide new research directions and advance the development of practical symmetric ORFBs.

关键词： Redox flow battery Symmetric battery Organic battery Aqueous electrolyte Non-aqueous electrolyte

Estimation of J—R curves for Small-Sized cOEc Specimens and Its Application considering crack-Tip cons tr aints

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Acta Mechanica Solida Sinica 2019年第3期32卷 261-276页

作者： G.W.he c.Bao L.x.cai Y.J.Wu Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and Engineering Southwest Jiaotong University Chengdu 610031 China

The normalization method has been employed to estimate the J-resistance (J—R) curves for c-shaped outside edge-notched compression (cOEc) specimens of SA-508 steel. The cOEc specimens present the lowest J—R curves in comparison with other three types of specimens. Based on the J—Q—M met hod, the constraint parame ter Q determined at the mid-plane in the through-thickness direction of the specimen is used to approximately quantify the threedimensional crack-tip constraint for cOEc specimens. combining with the previous experiments on J—R curves, the constraint-coirected J—R curves for SA-508 steel specimens are given, which may be used to predict the fracture toughness of actual cracked components in structural integrity assessment.

关键词： Ductile fracture toughness cOEc specimen Dimensionless load separation principle Normalization method crack-tip constraint J-Q-M method

Progress of Pattern Dynamics in Plasma Waves

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communications in computational Physics 2008年第10期4卷 1129-1150页

作者： B.Qiao c.T.Zhou x.T.he c.H.Lai center for Plasma Physics Department of Physics and AstronomyQueen’s University BelfastBelfast BT71NNUK Department of Physics National University of SingaporeSingapore 117542 Institute of Applied Physics and computational Mathematics P.O.Box 8009Beijing 100088China center for Applied Physics and Technology Peking UniversityBeijing 100871China Institute for Fusion Theory and Simulation Zhejiang UniversityHangzhou 310027China Beijing-Hong Kong-Singapore Joint centre for Nonlinear&complex Systems(Singapore) National University of SingaporeSingapore 117542.

This paper is concerned with the pattern dynamics of the generalized nonlinear Schrodinger equations(NSEs)relatedwith various nonlinear physical problems in *** theoretical and numerical results show that the higher-order nonlinear effects,acting as a Hamiltonian perturbation,break down the NSE integrability and lead to chaotic ***,coherent structures are destroyed and replaced by complex *** orbit crossings in the phase space and stochastic partition of energy in Fourier modes show typical characteristics of the stochastic *** investigations show that nonlinear phenomena,such as wave turbulence and laser filamentation,are associated with the homoclinic *** particular,we found that the unstable manifolds W(u)possessing the hyperbolic fixed point correspond to an initial phase θ=45° and 225° ,and the stable manifolds W(s)correspond toθ=135° and 315° .

关键词： Pattern dynamics homoclinic chaos nonlinear Schrodinger equations plasma waves

Amplitude modulation and extreme events in turbulent channel flow

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Acta Mechanica Sinica 2018年第1期34卷 1-9页

作者： Y.c.Yao W.x.Huang c.x.xu AML Department of Engineering Mechanics Tsinghua University

Amplitude modulation of near-wall turbulence by large-scale structures in the outer layer is investigated by direct numerical simulation of turbulent channel flows at Reynolds number Re= 540, 1000, 2000. The effect of modulation is obvious in the two-point cross-section correlation map, and the correlation coefficients increase significantly with the Reynolds number. The influence of modulation is reflected in the tail of the probability density function of the near-wall flow signals, which expands as the Reynolds number increases. The flatness factor provides a quantitative description of the high fluctuation events due to modulation. Vortical structures associated with modulation are revealed by conditionally averaging the flow field of the near-wall extreme events, providing a depiction of how the influence of the large-scale structures penetrate towards the near-wall region.

关键词： Wall turbulence Amplitude modulation Flatness Extreme events