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Synergetic deformation mechanisms in an Mg-zn-Y-zr alloy with intragranular lPSO structures

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Journal of Magnesium and Alloys 2023年第5期11卷 1754-1768页

作者： z.z.Peng X.h.Shao z.M.liang D.l.Wang l.W.Wang X.l.Ma hebei Key laboratory of Material Near-Net Forming Technology School of Materials Science and EngineeringHebei University of Science and TechnologyShijiazhuang 050018China Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of Sciences72 Whenua RoadShenyang 110016China

Deformation kink is one of the important strengthening mechanisms of the long-period-stacking-ordered(lPSO)phase containing magnesium(Mg)alloys,while the deformation twin is generally *** optimize the mechanical properties of lPSO containing Mg alloy by simultaneously exciting kink and twin,we successfully prepared the Mg-zn-Y-zr alloy featuring intragranular lPSO phase and free grain boundary lPSO phase by *** unraveled the corresponding strengthening and toughening mechanisms through transmission electron microscopy characterization and theoretical *** high strength and good plasticity of the homogenized alloy benefit from the synergistic deformation mechanism of multiple kinking and twining in the *** the activation of kinking and twinning depends on the thicknesses of lPSO lamellae and their relative *** results may shed light on optimizing the design of Mg alloys regulating the microstructure of lPSO phases.

关键词： Mg alloy lPSO distribution Kink Twin Transmission electron microscopy

iNFlUENCE OF lOCAl BRiTTlE zONE ON ThE FRACTURETOUGhNESS OF hiGh-STRENGTh lOW-AllOYEDMUlTiPASS WElD METAlS

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Acta Metallurgica Sinica(English letters) 1998年第2期11卷 87-92页

作者： z.l.zhou S.h.liu Dalian Railway inst Dalian China

in this paper, toughness properties and microstructurc of low-alloyed multipass welds with yield strength above 700MPa have 6een studied using the weld thermal simulation and throughout thickness CTOD fracture mechanics tests. impact testing of thermal simulated specimens showed that the primary weld metal and the fine gmmed weld metal had good toughness, while the coarse grained weld metal had the lowest toughness value as the local brittle zone (lBz) in multipass weld metals. Cleavage fracture in CTOD testing of thick multipass weld metals was initiated from martensite-austenite (MA) phases in the lBz. MA phases were distributed at the prior austenite grain boundaries and around ferrite grains. As the size of the local brittle zone along the fatigue crack front increases, CTOD frncture toughness of multipass weld metals decreases. The weakest link theory was used to evaluate effect of the local brittle zone on fracture toughness of thick multipass weld metals. The estimated curves agree well with the eaperimental data.

关键词： multipass weld metal local brittle zone weld thermal simulation CTOD fracture toughness

Ab initio STUDiES ON MAGNETiSM OF 3d TRANSiTiON METAl DiMERS

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Acta Metallurgica Sinica(English letters) 2007年第5期20卷 341-346页

作者： J.h. Gu z.l. zhu School of Physical Engineering and Material Physics laboratory Zhengzhou University Zhengzhou 450052 China

Ab initio calculations with the self-consistent full-potential linearized augmented-plane-wave method （FlAPW）, under generalized gradient approximation, have been carried out to describe the electronic and magnetic properties of 3d transition metal dimers. it predicted the antiferromagneticity of Cr2 and ferromagneticity of other species. The Mn2 dimer was shown to be ferromagnetic coupling with a local magnetic moment of 5μB. retaining the value of its free atom state. The V2 and Ni2 exhibited low spin-polarization with local magnetic moment of only 1μB per atom. On the other hand, Fe2 and Co2 were highly spin-polarized with local magnetic moments of 3 and 2μB.

关键词： magnetism 3d transition metal dimer ab initio calculation

Passive Q-switching in an erbium-doped fiber laser using tungsten sulphoselenide as a saturable absorber

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Chinese Optics letters 2018年第2期16卷 69-73页

作者： h.Ahmad z.C.Tiu S.i.Ooi Photonics Research Centre University of Malaya

A highly stable Q-switched laser incorporating a mechanically exfoliated tungsten sulphoselenide （WSSe） thin sheet saturable absorber （SA） is proposed and demonstrated. The SA assembly, formed by sandwiching a thin WSSe sheet between two fiber ferrules within the erbium-doped fiber laser, is used to effectively modulate the laser cavity losses. The WSSe-based SA has a saturation intensity of ~0.006 MW∕cm^2 and a modulation depth of 7.8%, giving an optimum Q-switched laser output with a maximum repetition rate of 61.81 khz and a minimum pulse width of 2.6 μs. The laser＇s highest output power of 0.45 mW and highest pulse energy of 7.31 nJ are achieved at the maximum pump power of 280.5 mW. The tunability of the cavity＇s output at the maximum pump power is analyzed with a C-band tunable bandpass filter, giving a broad tunable range of ~40 nm, from 1530 nm to 1570 nm. The output performance of the tunable Q-switched laser correlates well with the gain spectrum of erbium-doped fibers, with the shift in the gain profile as a result of the saturated SA.

关键词： Passive Q-switching in an erbium-doped fiber laser using tungsten sulphoselenide as a saturable absorber SA EDF

Snap-through of an elastica under bilateral displacement control at a material point

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Acta Mechanica Sinica 2020年第3期36卷 727-734页

作者： Q.Wang h.l.zou z.C.Deng Department of Engineering Mechanics Northwestern Polytechnical UniversityXi'an 710072China

Snap-through phenomenon widely occurs for elastic systems,where the systems lose stability at critical *** snapthrough of an elastica under bilateral displacement control at a material point is studied,by regarding the whole elastica as two components,i.e.,pinned-clamped ***,stiffness-curvature curves of two pinned-clamped elasticas are firstly efficiently located based on the second-order mode,which are used to determine the shapes of two *** transformations are used to assemble two components together to form the whole elastica,which reveals four kinds of *** advantage of this way compared with other methods such as the shooting method is that multiple coexisting solutions can be located accurately.O n the load-deflection curves,four branches correspond to four kinds of shapes and first two branches are symmetrical to the last two branches relative to the original *** the bilateral displacement control,the critical points can only appear at saddle-node bifurcations,which is different to that for the unilateral displacement ***,one critical point is found on the first branch and two critical points are found on the secondary *** addition,the snap-through among different branches can be well explained with these critical points.

关键词： Elastica Snap-through Critical points Buckling Displacement control

Nonplanar flow-induced vibrations of a cantilevered PiP structure system concurrently subjected to internal and cross flows

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Acta Mechanica Sinica 2019年第6期35卷 1241-1256页

作者： z.Y.liu T.l.Jiang l.Wang h.l.Dai Department of Mechanics Huazhong University of Science and TechnologyWuhan 430074China hubei Key laboratory for Engineering Structural Analysis and Safety Assessment Wuhan 430074China

Pipe-in-pipe(PiP)structures are widely used in offshore oil and gas pipelines to settle thermal insulation issues.A PiP structure system usually consists of two concentric pipes and one softer layer for thermal insulation *** total response of the system is related to the dynamics of both pipes and the interactions between these two concentric *** the current work,a theoretical model for flow-induced vibrations of a PiP structure system is proposed and analyzed in the presence of an internal axial flow and an external cross *** interactions between the two pipes are modeled by a linear distributed damper,a linear distributed spring and a nonlinear distributed spring along the pipe *** unsteady hydrodynamic forces due to cross flow are modeled by two distributed van der Pol wake *** nonlinear partial differential equations for the two pipes and the wake are further discretized by the aid of Galerkin’s technique,resulting in a set of ordinary differential *** ordinary differential equations are further numeri cally solved by using a fourth-order Runge-Kutta integration *** portraits,bifurcation diagrams,an Argand diagram and oscillation shape diagrams are plotted,showing the existence of a lock-in phenomenon and figure-of-eight *** PiP system subjected to cross flow displays some interesting dynamical behaviors different from that of a single-pipe structure.

关键词： Cantilevered PiP structure Theoretical model Flow-induced vibration Cross flow internal flow

Decorating crystalline YFe_(2-x)Al_(x) on the Mg_(60)la_(10)Ni_(20)Cu_(10) amorphous alloy as “hydrogen pump” to realize fast de/hydrogenation

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Journal of Materials Science & Technology 2024年第6期173卷 72-79页

作者： l.J.huang h.Wang l.z.Ouyang M.zhu h.J.lin School of Materials Science and Engineering Key Laboratory of Advanced Energy Storage Materials of Guangdong ProvinceSouth China University of TechnologyGuangzhou 510641China institute of Advanced Wear&Corrosion Resistance and Functional Materials Jinan UniversityGuangzhou 510632China

Mg-based amorphous alloys are one of the potential hydrogen storage materials but suffer from sluggish dehydrogenation/hydrogenation(de/hydrogenation)*** this work,as a new strategy,a hydrogen pump is built on the surface of amorphous alloys to solve this *** milling crystalline YFe_(2-x)Al_(x) hydrogen storage alloy with Mg_(60)la_(10)Ni_(20)Cu_(10) amorphous alloy,fine crystalline particles were seeded on amorphous alloy powder to form a“strawberry”*** to the TEM observation,a metallurgical bonding boundary formed between the Mg-based amorphous matrix and the Y-Fe-Al crystalline *** microstructure and de/hydrogenation kinetics investigation,the“hydrogen pump”effect of the seeded crystalline alloy was confirmed,which makes it much easier for the hydrogen to dissociate on and diffuse through the surface of the Mg-based amorphous *** such effect,the h absorption rate of Mg_(60)la_(10)Ni_(20)Cu_(10) amorphous alloy became almost eight times faster and it absorbs ~2.8 wt.% in 1 h at 130℃ under 4.5 MPa-h_(2).Further,fast hydrogenation can even achieve at 70℃ and the low-temperature dehydrogenation kinetics of the amorphous hydride can be also greatly *** present work proves that surface modification is of great importance for obtaining Mg-based amorphous alloy with ideal hydrogen storage performance.

关键词： hydrogen storage Mg-based amorphous alloy hydrogen pump Composite structure

Precipitation of multi-type nano-quasicrystals in a Mg-zn-Y alloy

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Journal of Magnesium and Alloys 2024年第3期12卷 997-1008页

作者： W.z.Wang X.z.zhou l.F.zhang h.Q.Ye z.Q.Yang Shenyang National laboratory for Materials Science Institute of Metal ResearchChinese Academy of ScienceShenyang 110016China Ji hua laboratory Foshan 528251China Foshan University Foshan 528231China

Mg-6zn-1Y(at.%)ribbons with strengthening precipitates of multi-type nanoquasicrystals were prepared by melt-spinning followed by aging *** evolution of the rapidly solidified ribbons during isothermal aging was comprehensively studied using various electron microscopy *** new kinds of decagonal quasicrystals were formed in aged ribbons,in addition to precipitation of nanometer icosahedral ***-resolution observations reveal that both decagonal quasicrystals can be modeled by quasiperiodic tiling with decagonal clusters of 2.5 nm in diameter,but overlap of neighboring clusters in both decagonal quasicrystals is different from the Gummelt model observed in other quasicrystals.A shell composed of complex laves Mg-zn domains was formed surrounding each decagonal quasicrystal precipitate upon prolonged *** addition,all kinds of nanoprecipitates exhibit excellent structure and size stability at 573 *** findings may have implications for not only fundamental studies about quasicrystals,but also microstructural manipulation of high-performance Mg alloys.

关键词： Quasicrystal Mg alloys Rapid solidification Scanning-transmission electron microscopy.

Rational design of AgGaS/znS/znS quantum dots with a near-unity photoluminescence quantum yield via double shelling scheme

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Journal of Materials Science & Technology 2024年第2期169卷 235-242页

作者： h.X.lu h.liu z.z.Fu Y.Y.Chen h.Q.Dai z.hu W.l.zhang R.Q.Guo institute for Electric light Sources School of Information Science and TechnologyFudan UniversityShanghai 200433China institute of Future lighting Academy for Engineering and TechnologyFudan UniversityShanghai 200433China Yiwu Research institute of Fudan University YiwuZhejiang 322000China zhongshan-Fudan Joint innovation Center Zhongshan 528437China

in this study,a two-step method was used to synthesize highly luminescent AgGaS/znS/znS quantum dots(QDs).in the first step,an inner znS shell was formed via a one-pot method,which resulted in a smaller lattice mismatch between the AgGaS core and the outer znS shell,thereby facilitating the formation of a thick outer *** the two-step shelling process,the synthesized AgGaS/znS/znS QDs showed an excellent photoluminescence quantum yield(PlQY)of 96.4%with a peak wavelength of 508 nm,repre-senting the highest PlQY reported thus far for AgGaS ***,the effect of halogen ions in zn precursors on the shelling process was *** was proposed that the capacity of halogen ions to coordinate with the QDs influenced the balance between zn cation diffusion and znS shelling ***,the znS shelling reaction was dominant when znCl_(2)was employed,while zn cation diffusion was the dominant process under the i^(−)-rich *** work provides insights into the interfacial restructuring during the znS shelling and offers a clear map for the tailored synthesis of core/shell QDs.

关键词： AgGaS Quantum dots Photoluminescence Core/shell Alloyed core/shell interface