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Suppressing Effect of Heat Treatment on the Portevin–Le Chatelier Phenomenon of Mg–4%Li–6%Zn–1.2%y Alloy

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Journal of Materials Science & Technology 2016年第12期32卷 1232-1238页

作者： C.Q.Li D.k.Xu B.J.Wang L.y.Sheng E.H.Han School of Materials Science and Engineering Northeastern University Shenyang 110819 China key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Environmental Corrosion Center Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China Shenzhen Institute Shenzhen Key Lab Human Tissue Regenerate and Repair Peking University Shenzhen 518057 China

Microstructural evolution and Portevin-Le Chatelier（PLC） phenomenon of the as-extruded Mg-4%Li-6%Zn-1.2%y alloy before and after heat treatment have been *** has been demonstrated that for the as-extruded and solid solution treated（T4） samples,the PLC phenomenon could be obviously observed on tensile stress-strain ***,the PLC phenomenon in T4 samples was more salient than that in the as-extruded condition,suggesting that the occurrence of PLC phenomenon was closely related to the super-saturation degree of solute atoms in the *** most of solute atoms were consumed for the formation of Mg Zn precipitates（β1′ and a little of β2′） during the subsequent ageing treatment（T6）,the PLC phenomenon of T6 samples was ***,due to the pinning effect of the formed Mg Zn precipitates on mobile dislocations,the tensile strength of T6 samples was relatively higher than those of the other two conditions.

关键词： Mg-Li alloy Heat treatment Portevin-Le Chatelier (PLC) effect Precipitates

Mechanics of granular column collapse in fluid at varying slope angles

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Journal of Hydrodynamics 2017年第4期29卷 529-541页

作者： k.kumar J.-y.Delenne k.Soga Computational Geomechanics Research Group Department of Engineering University of Cambridge IATE UMR 1208 INRA-CIRAD-Montpellier Supagro-UM2 University of Montpellier 2 Department of Civil and Environmental Engineering University of California

This paper investigates the effect of initial volume fraction on the runout characteristics of collapse of granular columns on slopes in fluid. 2-D sub-grain scale numerical simulations are performed to understand the flow dynamics of granular collapse in fluid. The discrete element method（DEM） technique is coupled with the lattice Boltzmann method（LBM）, for fluid-grain interactions, to understand the evolution of submerged granular flows. The fluid phase is simulated using multiple-relaxation-time LBM（LBM-MRT） for numerical stability. In order to simulate interconnected pore space in 2-D, a reduction in the radius of the grains（hydrodynamic radius） is assumed during LBM computations. The collapse of granular column in fluid is compared with the dry cases to understand the effect of fluid on the runout behaviour. A parametric analysis is performed to assess the influence of the granular characteristics（initial packing） on the evolution of flow and run-out distances for slope angles of 0 °, 2.5°, 5 ° and 7.5 °. The granular flow dynamics is investigated by analysing the effect of hydroplaning, water entrainment and viscous drag on the granular mass. The mechanism of energy dissipation, shape of the flow front, water entrainment and evolution of packing density is used to explain the difference in the flow characteristics of loose and dense granular column collapse in fluid.

关键词： Lattice Boltzmann method(LBM) discrete element method(DEM) granular column collapse granular flows hydroplaning water entrainment viscous drag

MAGNETIC PROPERTy chanGE IN AN AUSTENITIC STAINLESS STEEL SUBJECTED TO DAMAGE AT ELEVATED TEMPERATURE-MICROSTRUCTURE RESPONSIBLE FOR MAGNETIC PROPERTy

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Acta Metallurgica Sinica(English Letters) 2004年第4期17卷 387-392页

作者： y.Nagae k.Aoto Japan Nuclear Cycle Development Institute 4002 Narita Oarai Ibaraki 311-1393 JapanJapan Nuclear Cycle Development Institute 4002 Narita Oarai Ibaraki 311-1393 Japan

It has been found that magnetic property changes in austenitic stainless steel subjected to creep at high temperature. The change of magnetic property is mainly due to decrease the chromium concentration in the vicinity of grain boundary and transform into martensite in the area. However this result is for short-term creep. It is necessary to evaluate the long-term creep in order to develop non-destructive technique for plants. Moreover it is important to evaluate the fatigue. The change of magnetic property for those damages at high temperatures is investigated. The transformation into martensite is observed for both the long-term creep and fatigue. The magnetic regions are observed in sever deformed area and near crack. Then the formation of magnetic phases is related to the damage. The damage at high temperature can be universally evaluated.

关键词： creep fatigue high temperature austenitic stainless steel magnetism

Cutting Characteristics of Zr-Based Bulk Metallic Glass

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Journal of Materials Science & Technology 2015年第2期31卷 153-158页

作者： D.X.Han G.Wang J.Li k.C.chan S.To F.F.Wu y.L.Gao Q.J.Zhai Laboratory for Microstructures Shanghai University Department of Industrial and System Engineering The Hong Kong Polytechnic University

Cutting behavior exerts a considerable influence on the fabrication of bulk metallic glass(BMG) components. In this study,the influences of machining parameters(i.e.,depth of cutting,feed rate,and spindle rate) on the turned surface of a Zr-based BMG after observing the 3D morphologies of this surface were *** results showed that the influence of the spindle rate on the surface morphologies is more substantial as compared to the depth of cutting and the feed rate. Nanoscratch tests were conducted to further characterize the separation mechanism of the chips,which revealed that the chips are torn off the surface of a BMG because of inhomogeneous localized maximum shear stress.

关键词： Bulk metallic glass Ultra-precision machining Surf

Microstructure and properties of hot extruded AZ31-0.25%Sb Mg-alloy

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中国有色金属学会会刊：英文版 2008年第A01期18卷 17-21页

作者：田素贵王岭 k.y.SHON k.H.kIM School of Materials Sciences and Engineering Shenyang University of Technology Materials Engineering Department Korea Institute of Machinery and Materials

The effects of hot extrusion treatment on the microstructure and mechanical properties of AZ31-0.25%Sb Mg alloy were investigated by means of mechanical properties measurement and microstructure *** results show that the microstructure of AZ31-0.25%Sb Mg alloys consists ofα-Ms matrix,Mg_(17)Al_(12) and Mg_3Sb_2 *** ultimate tensile strength (UTS) and yield tensile strength(yTS) of the alloy are obviously enhanced by hot extrusion treatment,and the enhanced extent of UTS and yTS increases with the decrease of hot extrusion temperature,moreover,the yTS value of the alloy at RT,after extruded at 220℃,increases up to 131.4%,which attributes to the finer grains resulted from the dynamic recrystallization occurred during hot *** hot extrusion goes on,the slipping and concentration of dislocations continue to occur within the finer grains,which promotes the formation of the subgrains in the *** deformation features of the extruded alloy during tensile deformation at RT are the twinning deformation and dislocation slipping in the twinning ***,the deformation mechanisms of the alloy are a dislocation activation on the basal plane and a+c dislocation activation on the pyramidal planes.

关键词：镁合金高温挤压处理微观结构

Computational fluid dynamics simulation of the wind flow over an airport terminal building

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第6期11卷 389-401页

作者： Chun-ho LIU Dennis y.C.LEUNG Alex C.S.MAN P.W.chan Department of Mechanical Engineering The University of Hong Kong Hong kong Observatory

Turbulence in the wake generated by wind flow over buildings or obstacles may produce complex flow patterns in downstream *** include the recirculating flow and wind deficit areas behind an airport terminal building and their potential impacts on the aircraft landing on nearby runways.A computational fluid dynamics(CFD) simulation of the wind flow over an airport terminal building was performed in this study of the effect of the building wake on landing *** normal meteorological conditions,the studied airport terminal building causes limited effects on landing aircraft because most of the aircraft have already landed before entering the turbulent wake *** simulating the approach of a tropical cyclone,additional CFD sensitivity tests were performed to study the impacts of building wake under extreme meteorological *** was found that,in a narrow range of prevalent wind directions with wind speeds larger than a certain threshold value,a substantial drop in wind speed(>3.6 m/s) along the glide path of aircraft was observed in the building *** CFD results also showed that under the most critical situation,a drop in wind speed as large as 6.4 m/s occurred right at the touchdown point of landing aircraft on the runway,an effect which may have a significant impact on aircraft *** study indicated that a comprehensive analysis of the potential impacts of building wake on aircraft operations should be carried out for airport terminals and associated buildings in airfields to ensure safe aviation operation under all meteorological conditions and to facilitate implementation of precautionary measures.

关键词： Aviation safety Building aerodynamics Computational fluid dynamics (CFD) k-e turbulence model Tropicalcyclone

Light Curve Analysis and Period Study of Two Eclipsing Binaries UZ Lyr and BR Cyg

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Research in Astronomy and Astrophysics 2022年第2期22卷 135-142页

作者： k.y.Roobiat R.Pazhouhesh Department of Physics Faculty of SciencesUniversity of BirjandBirjandIran

Two eclipsing binary systems,UZ Lyr and BR Cyg,are semi-detached types whose secondary component fills its Roche *** radial velocity and light curves of these systems have already been investigated separately,both their radial velocity and light curves are analyzed simultaneously for the first time in the present ***,the orbital period changes of these systems are *** results show that the mass transfers between components have negligible effects on the orbital period changes of these systems,but two light travel time effects are the reasons for the periodic behavior of the O-C curve for UZ *** could not remark more information about orbital period changes for BR Cyg,but we find a new orbital period for *** radial velocity and light curve analysis,we find a cold spot on the secondary component of BR *** new geometrical and physical parameters of both systems are obtained and their positions on the H-R diagram are demonstrated.

关键词： (stars:)binaries(including multiple):close (stars:)binaries:eclipsing stars:individual(UZ Lyr BR Cyg)

A G^E/Equation of State Mixing Rule for Vapor-Liquid Equilibria

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Chinese Journal of Chemical Engineering 1998年第3期6卷 14-28页

作者：屈一新汪文川 Lee y.y. Chung k.y. Lee y.W. korea Institute of Science and Technology SeoulKorea

A new excess Gibbs free energy/equation of state type mixing 0rule was derived byremoving the infinite pressure boundary condition imposed by Wong and *** mixing rulewas extensively tested in terms of a comprehensive data base,consisting of 52 simple nonpolar-nonpolar,carbon dioxide containing,hydrocarbon-hydrocarbon,CFC,polar-polar,nonpolar-polarbinary and multicomponent *** on the complete predictive capability,a comparisonbetween the Wong-Sandler and the mixing rule proposed was *** results indicate that thenew mixing rule is in general superior to the Wong-Sandler’s,and the binary interaction parameteras required by the latter is removed,which reduces computing effort and is reliable in predictions ofvapor-liquid equilibria from low pressures to high pressures.

关键词： vapor-liquid equilibria equation of state mixing rule

Nanotexturing and Wettability Ageing of Polypropylene Surfaces Modified by Oxygen Capacitively Coupled Radio Frequency Plasma

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Journal of Materials Science & Technology 2014年第10期30卷 965-972页

作者： y.P.Li M.k.Lei Surface Engineering Laboratory School of Materials Science and EngineeringDalian University of Technology

Polypropylene （PP） was treated by an oxygen capacitively coupled radio frequency plasma （CCP） under a radio frequency （RF） power of 200 W for exposure time of 1, 5, and 10 rain. The ageing process of the plasma- treated PP was studied at an ageing temperature of 90 ~C during an ageing time up to 25 h. The formation of the nanotextures with different geometry and aspect ratio and the grafting of large number of oxygen- containing groups were achieved on as-treated PP surfaces under the oxygen CCP treatment for the increased exposure time. The hydrophilicity on the as-treated PP surfaces with the stable nanotextures was rapidly depressed during the ageing process at 90 ℃ due to the restructuring of chemical composition. The surface restructuring rate was dependent on the aspect ratio and the oxygen-containing groups on the nanotextured PP with increasing exposure time. The hydrophobic over-recovery to high hydrophobicity and superhydrophobicity were observed on the post-aged surfaces with the stable nanofibrils from as-treated hydrophilic surfaces. The superhydrophobicity with the low water adhesion was achieved on the post-aged surfaces preserving the nanofibrils with high aspect ratio and large distance due to the decrease of the oxygen-containing groups after the surface restructuring.

关键词： Polypropylene Plasma nanotexturing Ageing Surface restructuring Superhydrophobicity