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INVEsTIGATION ON ThE DENsITY UNIFORMITY OF PREssED PARTs bY LOw-VOLTAGE ELECTROMAGNETIC COMPACTION

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Acta Metallurgica sinica(English Letters) 2004年第6期17卷 805-811页

作者： s.Y.huang Z.h.Meng Y.C.Li b.Zhang w.Ouyang harbinInstituteofTechnology Harbin150001China／／WuhanUniversityofTechnologyWuhan430070China wuhanUniversityofTechnology Wuhan430070China

Powder metallurgy is an efficient approach to fabricate varieties of high performance structure materials, function materials and special materials working under limited conditions. Research and development of new efficient technology to form high-density, high-performance and net shape parts is a key to widen application and development of powder materials. Recently, the low-voltage electromagnetic compaction (EMC) has been used by present authors to compacted copper, tin, aluminum powders and the products with 99% relative density have been acquired. In this work, the research has been extended to investigation on the density uniformity of pressed parts. The analysis results show that the density of the part compacted by low-voltage EMC decreases gradually in press direction as static compaction. but it is higher and more homogeneous. The density of the top part increases gradually from the center to the outer, which is just reversal of the bottom part. In some extent, the higher the discharging voltage is, the higher the density is and the more homogeneous the distribution is. In addition, repetitive compaction can improve the density of powder parts and the distribution uniformity.

关键词： powder low-voltage electromagnetic compaction density uniformity density distribution

A strategy for designing stable nanocrystalline alloys by thermo-kinetic synergy

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Journal of Materials science & Technology 2020年第8期36卷 21-31页

作者： h.R.Peng b.s Liu F.Liu state Key Laboratory of solidification Processing Northwestern Polytechnical UniversityXi’an710072China school of Materials and Chemical Engineering Xi’an Technological UniversityXi’an710021China Analytical and Testing Center Northwestern Polytechnical UniversityXi’an710072China

Aiming to design stable nanocrystalline(NC)materials,so far,it has been proposed to construct nanostructure stability maps in terms of thermodynamic parameters,while kinetic stabilization has seldom been considered,despite the synergy of thermodynamics and ***,the thermodynamically stabilized NC materials may be easily subjected to grain growth at high temperatures due to the weakly kinetic *** from the thermo-kinetic synergy,a stabilization criterion is proposed as a function of intrinsic solute parameters(*** activation energy for bulk diffusion and the segregation enthalpy),intrinsic solvent parameters(*** intrinsic activation energy for Gb migration and the Gb energy)and processing parameters(*** grain size,the temperature and the solute concentration).Using first-principles calculations for a series of combinations between fifty-one substitutional alloying atoms as solute atoms and Fe atom as fixed solvent atom,it is shown that the thermal stability neither simply increases with increasing the segregation enthalpy as expected by thermodynamic stabilization,nor monotonically increases with increasing the activation energy for bulk diffusion as described by kinetic *** combination of thermodynamic and kinetic contributions,the current stabilization criterion evaluates quantitatively the thermal stability,thus permitting convenient comparisons among NC materials involved by various combinations of the solute atoms,the solvent atoms,or the processing *** of this thermo-kinetic stabilization criterion has been tested by current experiment results of Fe-Y alloy and previously published data of Fe-Ni,Fe-Cr,Fe-Zr and Fe-Ag alloys,etc.,which opens a new window for designing NC materials with sufficiently high thermal stability and sufficiently small grain size.

关键词： Thermo-kinetic synergy Criterion Thermal stability Nanocrystalline materials

Enhanced cavitation erosion resistance of a friction stir processed high entropy alloy

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International Journal of Minerals,Metallurgy and Materials 2020年第10期27卷 1353-1362页

作者： Rakesh b.Nair h.s.Arora harpreet singh Grewal surface science and Tribology Lab Department of Mechanical EngineeringShiv Nadar UniversityGautam Buddha NagarUttar Pradesh 203207India

Friction stir processing of an Al0.1CoCrFeNi high entropy alloy(hEA)was performed at controlled cooling conditions(ambient and liquid submerged).Microstructural and mechanical characterization of the processed and as-cast hEAs was evaluated using electron backscatter diffraction,micro-hardness testing and *** under the submerged cooling condition showed elongated grains(10μm)with fine equiaxed grains(2μm)along the boundary compared to the coarser grain(~2 mm)of as-cast *** hardness showed remarkable improvements with four(submerged cooling condition)and three(ambient cooling condition)times that of as-cast hEA(hV^150).The enhanced hardness is attributed to the significant grain refinement in the processed *** erosion behavior was observed for samples using an ultrasonication *** of the hEAs showed better cavitation erosion resistance than the stainless steel *** sample processed under a submerged liquid condition showed approximately 20 and 2 times greater erosion resistance than stainless steel 316L and ascast hEA,*** enhanced erosion resistances of the processed hEAs correlate to their increased hardness,resistance to plasticity,and better yield strength than the as-cast *** surface of the tested samples showed nucleation and pit growth,and plastic deformation of the material followed by fatigue-controlled disintegration as the primary material removal mechanism.

关键词： cavitation erosion microstructure mechanical properties surface engineering

A carbuncle cure for the harten-Lax-van Leer contact(hLLC)scheme using a novel velocity-based sensor

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Applied Mathematics and Mechanics(English Edition) 2021年第9期42卷 1259-1278页

作者： U.s.VEVEK b.ZANG T.h.NEw Department of Mechanical Materials and Aerospace EngineeringUniversity of LiverpoolLiverpool L693BXUnited Kingdom Department of Aerospace Engineering University of BristolBristol BS81TRUnited Kindgdom school of Mechanical and Aerospace Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore

A hybrid numerical flux scheme is proposed by adapting the carbunclefree modified harten-Lax-van Leer contact(hLLCM) scheme to smoothly revert to the harten-Lax-van Leer contact(hLLC) scheme in regions of shear. This hybrid scheme, referred to as the hLLCT scheme, employs a novel, velocity-based shear sensor. In contrast to the non-local pressure-based shock sensors often used in carbuncle cures, the proposed shear sensor can be computed in a localized manner meaning that the hLLCT scheme can be easily introduced into existing codes without having to implement additional data structures. Through numerical experiments, it is shown that the hLLCT scheme is able to resolve shear layers accurately without succumbing to the shock instability.

关键词： carbuncle shock instability Euler equation numerical flux harten-Laxvan Leer contact(hLLC)scheme

Influence of rare earth on the microstructure and age hardening response of indirect-extruded Mg-5sn-4Zn alloy

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Journal of Rare Earths 2010年第5期28卷 785-789页

作者：程伟丽 PARK s s 唐伟能 KOO b h school of Nano & Advanced Materials Engineering Changwon National University Light Metals Research Group Korea Institute of Materials Science (KIMS)

The effects of Ce addition on the microstructure, age hardening response and mechanical properties of an indirect-extruded Mg-5wt.%sn-4Zn (TZ54) alloy were investigated. Addition of Ce accelerated the aging response with the peak aging time moving from 300 h in TZ54 to 30 h in Mg-5wt.%sn-4Zn-1Ce (TZE541), while the peak harness was similar to each other. The addition of Ce also caused an increase in the precipitation stability during overageing. Though the tensile strength of extruded TZ54 was improved by t...

关键词： magnesium alloy extrusion microstructure aging response rare earths

Contributions of burst-sweep cycles to Reynolds shear stress over fluvial obstacle marks generated in a laboratory flume

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International Journal of sediment Research 2012年第3期27卷 378-387页

作者： h.MAITY b.s.MAZUMDER Fluvial Mechanics Laboratory Physics and Applied Mathematics UnitIndian Statistical Institute

This paper investigates the phenomena of turbulent bursting events,and to make a comparative study among the events in the scour geometry developed by short circular cylinders of fixed length with different diameters placed on the sand bed transverse to the *** distributions of turbulent kinetic energy(TKE),turbulent diffusion in both longitudinal and vertical directions at different locations of scour marks,and the contributions of burst-sweep cycles to the Reynolds shear stress are presented.

关键词： scour marks TKE Turbulent diffusion Reynolds stress bursting events

Relativistic symmetries of Deng Fan and Eckart potentials with Coulomb-like and Yukawa-like tensor interactions

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Chinese Physics b 2014年第10期23卷 45-55页

作者： Akpan N.Ikot s.Zarrinkamar b.h.Yazarloo h.hassanabadi Theoretical Physics Group Department of Physics University of Port Harcourt Choba PMB 5323 Port Harcourt Nigeria Department of basic sciences Garmsar Branch Islamic Azad University Garmsar Iran Department of basic sciences Shahrood Branch Islamic Azad University Shahrood Iran

Relativistic symmetries of the Dirac equation under spin and pseudo-spin symmetries are investigated and a combina- tion of Deng-Fan and Eckart potentials with Coulomb-like and Yukawa-like tensor interaction terms are considered. The energy equation is obtained by using the Nikiforov-Uvarov method and the corresponding wave functions are expressed in terms of the hypergeometric functions. The effects of the Coulomb and Yukawa tensor interactions are numerically discussed as well.

关键词： Deng-Fan potential Eckart potential Nikiforov-Uvarov method spin and pseudo-spin symme-tries

Numerical modelling of a low power non-transferred arc plasma reactor for methane conversion

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Plasma science and Technology 2019年第6期21卷 29-37页

作者： b I MIN D K DINh D h LEE T h KIM s ChOI Institute for Nuclear science and Technology Jeju National University 102 Jejudaehak-ro Jeju 63243Republic of Korea University of science and Technology(UsT) 217 Gajeong-ro Yuseong-gu Daejeon 34113 Republic of Korea Korea Institute of Machinery and Materials 156 Gajeongbuk-ro Yuseong-gu Daejeon 34103 Republic of Korea Department of Nuclear and Energy Engineering Jeju National University 102 Jejudaehak-ro Jeju 63243Republic of Korea

Thermal flow characteristics and the methane conversion reaction in a low power arc plasma reactor for efficient storage and transport of methane,which is the main component of shale gas,were *** temperature and velocity distributions were calculated according to the type of discharge gases and arc current level by a self-developed magnetohydrodynamics (MhD)code and a commercial ANsYs-FLUENT code;the transport of chemical species was analyzed as including the chemical reactions of methane *** simulated results were verified by the comparison of calculated and measured arc voltages with permissible low error as under 4%.Three C2 hydrocarbon gases with ethane (C2h6),ethylene (C2h4),and acetylene (C2h2)were selected as the converted species of methane from experimental *** mass fraction of C2 hydrocarbons and hydrogen as the product of the conversion reaction at the reactor was also *** values show good agreement with the actual experimental results in that the major conversion reaction occurred in C2h2 and hydrogen,and the conversions to C2h6,C2h4,and hydrogen were minor reactions of methane pyrolysis conversion.

关键词： numerical modelling non-transferred arc plasma methane chemical reaction

Effect of Plastic Deformation on Magnetic Properties of Fe-40%Ni-2%Mn Austenitic Alloy

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Journal of Iron and steel Research International 2007年第4期14卷 56-60页

作者： selva büyükakka■ h Aktas s Akturk Physics Department Nigde UniversityNigde 51100NigdeTurkey Physics Department Kirikkale UniversityYahsihan 71450KirikkaleTurkey

The effects of plastic deformation on the magnetic properties of austenite structure in an Fe-40% Ni-2 % Mn alloy is investigated by using Mossbauer spectroscopy and Differential scanning Calorimetry （DsC） techniques The morphology of the alloy has been obtained by using scanning Electron Microscopy （sEM）. The magnetic behaviour of austenite state is ferromagnetic. After plastic deformation, a mixed magnetic structure including both paramagnet- ic and ferromagnetic states has been obtained at the room temperature. The volume fraction changes, the effective hyperfine fields of the ferromagnetic austenite phase and isomery shift values have also been determined by Mossbauer spectroscopy. The Curie point （Tc） and the Neel temperature （TN） have been investigated by means of DsC system for non-deformed and deformed Fe-Ni-Mn alloy. The plastic deformation of the alloy reduces the TN and enhances the paramagnetic character of austenitic Fe-Ni-Mn alloy.

关键词： Mossbauer spectroscopy differential scanning calorimetry (DsC) scanning electron microscopy (sEM) plastic deformation magnetically ordered material ferromagnetic austenite