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Rotational and translational domains of beta precipitate in aged binary Mg-Ce alloys

journal of Magnesium and Alloys 2021年第3期9卷 1039-1056页

作者： B.z.Sun H.x.zhang Y.Dong j.x.Ren Y.Tian g.M.xie j.Tan Y.H.Sun Na xiao School of Materials Science and Engineering Northeastern UniversityShenyang 110819China State Key Lab Rolling&Automat Northeastern UniversityShenyang 110819China Key Laboratory for Anisotropy and Texture of Materials Ministry of EducationNortheastern UniversityShenyang 110819China Analytical and Testing Center Northeastern UniversityShenyang 110819China

The structural evolution fromβ_(1)(Mg_(3)Ce)toβ(Mg_(12)Ce)precipitates,which takes place at the over-aged stage of binary Mg-Ce alloys,are investigated by high-angle annular dark-field scanning transmission electron *** structural transformation mainly occurs in the{111}_(β1)crystallographic planes,where the newly formedβlattices exhibit two categories of domain structures,namely rotational and translational *** rotational domain is composed of threeβdomains(β_(RA),β_(RB)andβ_(RC)),which are related by a 120°rotation with respect to each other around the 111_(β1)axis of theirβ_(1)parent ***{111}_(β1)crystallographic planes can provide four sets of sublattices with the same orientation for an initial nucleation ofβ*** leads to the formation of four translationalβdomains(β_(TA),β_(TB),β_(TC)andβ_(TD)),among which any two differ by a vector of 1/6112_(β1).We deduce theoretically that there exist twenty-fourβdomains during this ***,considering the interfacial misfit,only one-third of domains can grow up and eventually formsβ***,a majority ofβribbons overlap partiallyβ_(1)plate,which is beneficial to relax interfacial strain amongβ,β_(1)andα-Mg matrix(α/β/β_(1)).The configuration of multipleβdomains can effectively regulate interfacial misfit ofα/βandβ/β_(1),which are responsible for enhancing the hardness and strength of Mg-Ce ***,this study aims to provide some clues to improve the over-aged performance of magnesium alloys by constructingβdomains and optimizing theα/β/β_(1)interface.

关键词： Magnesium alloys HAADF-STEM Rotational domain Translational domain Phase transition Interfacial misfit

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Microstructure and mechanical properties of double-side friction stir welded 6082Al ultra-thick plates

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journal of Materials Science & Technology 2020年第6期41卷 105-116页

作者： C.yang j.F.zhang g.N.Ma L.H.Wu x.M.zhang g.z.He P.xue D.R.Ni B.L.xiao K.S.Wang.z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China CRRC Changchun Railway Vehicles Co. Ltd.Changchun 130062China School of Metallurgical Engineering Xi’an University of Architecture and TechnologyXi’an 710055China

In the present work,80 mm thick 6082Al alloy plates were successfully double-side welded by friction stir welding(FSW).The relationship between the microstructures and mechanical properties was built for the double-side FSW butt joint with more attention paid to the local characteristic *** was shown that a phenomenon of microstructural inhomogeneity existed in the nugget zone(Nz)through the thickness *** grain size presented an obvious gradient distribution from the top to the bottom for each single-pass weld,and the microhardness values decreased from both surfaces to the middle of the *** lowest hardness zone(LHz)exhibited a"hyperbolical"-shaped distribution extending to the middle of the *** tensile properties were obtained in the three sliced specimens of the FSW joint,and the joint coefficient reached about 70%which achieved the same level as the conventional FSW Al alloy *** element modeling proved that the"hyperbolical"-shaped heat affected zone(HAz)was beneficial to resisting the strain concentration in the middle layer specimen which helped to increase the tensile *** on the analysis of the hardness contour map,tensile property and microstructural evolution of the joints,an Isothermal Softening Layer(ISL)model was proposed and established,which may have a helpful guidance for the optimization on the FSW of ultra-thick Al alloy plates.

关键词： Ultra-thick aluminum alloy plates Double-side friction stir welding Finite element model Microstructural inhomogeneity Mechanical properties

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Revealing the high-frequency attenuation mechanism of polyurea-matrix composites

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Acta Mechanica Sinica 2020年第1期36卷 130-142页

作者： j.Cheng.z.L.Liu C.C.Luo T.Li z.j.Li Y.Kang.z.zhuang Applied Mechanics Laboratory School of Aerospace EngineeringTsinghua UniversityBeijing100084China Key Laboratory of Advanced Materials of Ministry of Education Department of Chemical EngineeringTsinghua UniversityBeijing100084China School of Materials Science and Engineering Tsinghua UniversityBeijing100084China

In this paper,a method for analyzing the high-frequency attenuation property of polyurea-matrix composites is developed by combining experimental,computational and theoretical ***,the ultrasonic experimental platform is established by solving the difficulties of high-frequency ultrasonic testing as high-frequency signal distortion,insufficient driving voltage and sampling rate failure,to study the dynamic mechanical properties(1-5 MHz)of pure polyurea and polyurea-matrix ***,the influences of composite parameters including the size and volume fraction of inclusions on wave attenuation performance under different frequencies are obtained and further verified by numerical ***,the contribution of inclusions to the wave attenuation performance is also theoretically *** is found that the increase of inclusion volume fraction and inclusion diameter will increase the attenuation coefficient of the *** the attenuation of composites with the inclusions of a 150-μm diameter and 30%as volume fraction can be 82%higher than pure *** amplifying attenuation effect of inclusions is mainly attributed to the scattering effect,which is verified by comparing numerical and theoretical results.

关键词： Polyurea Viscoelastic Dynamic mechanical properties Ultrasound

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An SBFEM-Based Model for Hydraulic Fracturing in Quasi-Brittle Materials

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Acta Mechanica Solida Sinica 2018年第4期31卷 416-432页

作者： F. Yao z.j. yang Y.j. Hu College of Civil Engineering and Architecture Zhejiang University Hangzhou 310058 China School of Civil Engineering Shaoxing University Shaoxing 312000 China

A numerical model based on the scaled boundary finite element method is devel- oped to simulate the hydraulic fracturing in concrete-like quasi-brittle materials using cohesive interface elements. The shadow domain method developed previously （yang and Deeks in Eng Fract Mech 143（4）：333 354, 2007） is extended to consider crack-width-dependent hydraulic pres- sure and cohesive traction, so that the stress intensity factors caused by both crack-face forces are semi-analytically calculated separately in the same way. The crack propagation is determined by the criterion of KI ≥ 0, and the propagation direction by the linear elastic fracture mechanics criteria. Two examples of concrete structures are modeled, and the results are in good agreement with the experimental data and others numerical results.

关键词： Scaled boundary finite element method Hydraulic fracture Cohesive crackmodel Crack propagation

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xPS INVESTIgATION OF NITROgEN IONS IMPLANTED INTO ALUMINUM ALLOY BY PLASMA BASED ION IMPLANTATION

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Acta Metallurgica Sinica(English Letters) 1999年第5期12卷 771-776页

作者： zhan, z.j. Ma, x.x. xia, L.F. Sun, Y. Harbin Inst of Technology Harbin China

Aluminum alloy 2024 has been implanted with nitrogen ions at various doses by plasma based ion implantation. The introduction of energetic ions causes structural change within the near surface region of the solid. The samples have been characterized by x-ray Photoelectron Spectroscopy at various depths. The chemical states of Al and N were identified by deconvolution of the recorded xPS spectra. After plasma based ion implanted nitrogen into aluminum, not only the AlN precipitates but also super saturated solution of nitrogen forms. The presence of aluminum in different chemical states is corresponding to Al, AlN and Al2O3. The majority of nitrogen is in the form of the supersaturated solution. With the increase of nitrogen dose, the amount of AlN precipitates increases.

关键词： Aluminum compounds Ion implantation Nitrides Nitrogen Plasma devices Wear of materials

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MODELLINg FOR PREDICTION OF CONTINUOUS COOLINg TRANSFORMATION KINETICS OF HOT-DEFORMED AUSTENITE STEEL

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Acta Metallurgica Sinica(English Letters) 1998年第3期11卷 225-229页

作者： j.B.Qu z.D.Wang x.H.Liu g.D.Wang Northeastern Univ Shenyang China

On the thermodynamics basis of regular solution sub-lattice model and soperelement model, kinetics basis of Cahn's transformation kinetics theory, and according to Scheil's additivity rule and eoperimental results obtained by thermal dilation method,a prediction model of transformations from hot-deformed austenite to ferrite, pearlite and bainite in low alloy steels, which could be applied to continuoas cooling process, is developed. The calculated transformed junctions of each phase based on laboratory controlled rolling and controlled cooling conditions in a low alloy steel are in reasonable agreement with the measured ones.

关键词： transformation kinetics thermodynamics continuous cooling,hot-deformed austenite

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Relationship of Corrosion Behavior Between Single-Phase Equiatomic CoCrNi,CoCrNiFe,CoCrNiFeMn Alloys and Their Constituents in NaCl Solution

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Acta Metallurgica Sinica(English Letters) 2021年第11期34卷 1574-1584页

作者： D.P.Wang j.W.Shen z.Chen F.g.Chen P.Y.guo Y.x.geng Y.x.Wang School of Materials Science and Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China

The composition is a significant issue for corrosion resistance of metallic *** reveal the correlation of corrosion behavior between multiprinciple alloys and their constituents,a series of single-phase equiatomic alloys of CoCrNi,CoCrNiFe and CoCrNiFeMn was *** electrochemical and scanning electron microscope results demonstrated that corrosion resistance of the equiatomic alloys in 0.1 M NaCl solution is located in the range but not the average value of their constituents.x-ray photoelectron spectroscopy analysis indicated that the protective performance of passive film is mainly determined by the constituent with the highest corrosion resistance and the breakdown of passive film is mainly dominated by the elements with the highest corrosion *** findings can guide the materials design of multiprinciple alloys with expected corrosion performance.

关键词： High-entropy alloy Corrosion Constituent x-ray photoelectron spectroscopy(xPS) Passive films

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A Parameter–Free generalized Moment Limiter for High-Order Methods on Unstructured grids

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Advances in Applied Mathematics and Mechanics 2009年第4期1卷 451-480页

作者： Michael yang z.j.Wang Department of Aerospace Engineering and CFD Center Iowa State UniversityAmesIA 50011USA

A parameter-free limiting technique is developed for high-order unstructured-grid methods to capture discontinuities when solving hyperbolic conservation *** technique is based on a“troubled-cell”approach,in which cells requiring limiting are first marked,and then a limiter is applied to these marked cells.A parameter-free accuracy-preserving TVD marker based on the cell-averaged solutions and solution derivatives in a local stencil is compared to several other markers in the literature in identifying“troubled cells”.This marker is shown to be reliable and efficient to consistently mark the *** a compact highorder hierarchical moment limiter is developed for arbitrary unstructured *** limiter preserves a degree p polynomial on an arbitrary *** a result,the solution accuracy near smooth local extrema is *** results for the high-order spectral difference methods are provided to illustrate the accuracy,effectiveness,and robustness of the present limiting technique.

关键词： Limiter shock-capturing high-order unstructured grids

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Tunability of the mechanical properties of(Fe_(50)Mn_(27)Ni_(10)Cr_(13))_(100-x)Mo_(x) high-entropy alloys via secondary phase control

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journal of Materials Science & Technology 2021年第14期73卷 210-217页

作者： Raymond Kwesi Nutor Q.P.Cao x.D.Wang D.x.zhang j.z.jiang International Center for New-Structured Materials(ICNSM) Laboratory of New-Structured MaterialsState Key Laboratory of Silicon Materialsand School of Materials Science and EngineeringZhejiang UniversityHangzhou 310027China State Key Laboratory of Modern Optical Instrumentation Zhejiang UniversityHangzhou 310027China

The single-phase face-centered cubic(fcc)-structured Fe_(50)Mn_(27)Ni_(10)Cr_(13) high entropy alloy(HEA)exhibits good ductility but low strength,which presents a *** Mo-alloying and thermomechanical treatments,we have designed the(Fe_(50)Mn_(27)Ni_(10)Cr_(13))_(100-x)Mo_(x)(x=0-6 at.%)alloy series with a wide range of mechanical *** careful control of secondary phases introduced in the cold-rolled and annealed(Fe_(50)Mn_(27)Ni_(10)Cr_(13))Mo_(2) sample resulted in an enhanced tensile strength from 250 MPa to 665 MPa,still having~25%*** investigations of this alloy revealed the presence of deformation twins,dislocation cells,and ordered bcc na no-pa rticles embedded in the ductile fcc matrix *** observed deformation structures are an indication of succes s ful cooperation between deformation twinning and precipitation strengthening in enhancing the tensile strength at maintained ductility compared to its cast *** work provides insight into the tunability of the mechanical properties of non-equiatomic HEAs via alloying and thermomechanical processing.

关键词： High-entropy alloys Mechanical property TEM

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Helicity Amplitude Analysis of z_c(3900)~± in e^+e^- →π^+π^-j/ψ

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Chinese Physics Letters 2016年第6期33卷 9-11页

作者：平荣刚 j.g.Messchendorp 苑长征 Institute of High Energy Physics Chinese Academy of Sciences KVI-CART University of Groningen

It is crucial to determine the spin and parity （jR） of zc（3900）＋ for understanding its structure. We perform a helicity amplitude analysis on zc（3900）＋ in the process e＋e- →π＋π-j/φ＊ with the hypotheses jP = 0-, 1＋, 1-, 2＋ and 2-. To estimate the significance of jP = 1＋ over other hypotheses, we perform a Monte Carlo simulation study, and we also discuss the prospect of measuring the spin parity in the future experiment with a large data sample.

关键词： of on is Helicity Amplitude Analysis of z_c in e for that

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