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Oxidation behavior and microstructural evolution of FeCoNiTiCu five-element high-entropy alloy nanoparticles

Journal of Materials Science & Technology 2024年第10期177卷 133-141页

作者： H.Bai R.Su R.Z.Zhao C.l.Hu l.Z.Ji y.J.liao y.N.Zhang y.X.li X.F.Zhang key laboratory for Anisotropy and Texture of Materials(MOE) School of Materials Science and EngineeringNortheastern UniversityShenyang110819China Institute of Advanced Magnetic Materials College of Materials and Environmental EngineeringHangzhou Dianzi UniversityHangzhou310012China

High-entropy alloys(HEAs)have attracted extensive attention ascribed to their unique physical and chemical properties induced by the cocktail ***,their oxidation behaviors,in particular at nanoscale,are still lack because of multi-element complexity,which could also be completely differ-ent from the bulk *** this work,we synthesized FeCoNiTiCu five-element HEA nanopar-ticles(NPs)with uniform elemental distribution by arc-discharging approach,and further investigated their oxidation behaviors at 250 ℃,and 350 ℃.The morphology,structure and element distribution of NPs were analyzed by transmission electron microscopy(TEM),energy dispersive spectroscopy(EDS)and electron energy loss spectroscopy(EElS).The surface oxidation in FeCoNiTiCu NPs during the high-temperature process can induce nanoscale pores at core/shell interfaces by kirkendall effect,and even the eventual coalescence into a single ***,the oxidation states of NPs with diameters(d)varying from 60 to 350 nm were analyzed in detail,revealing two typical configurations:hollow(dyolk-shell structures(d>150 nm).The experimental results were complemented by first-principles calculations to investigate the diffusion behaviors of five elements,evidencing that the surface oxidation strongly alters the surface segregation preferences:(1)in the initial stage,Cu and Ni appear to prefer segregating on the surface,while Co,Ti and Fe tend to stay in the bulk;(2)in the oxidation process,Cu prefers to stay in the center,while Ti segregates to the surface ascribed to the reduced po-tential *** study gives new insights into oxidation of nanoscale HEA,and also provides a way for fabrication of high-entropy oxides with controllable architectures.

关键词： High-entropy alloy Nanoparticles Oxidation kirkendall effect Exchange bias effect

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Study of k*（892）0 and ?（1020） meson production in proton–proton and Pb–Pb collisions at ■=2.76 TeV

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Communications in Theoretical Physics 2021年第2期73卷 93-99页

作者： y Ali M Ahmed A Arif Q Ali u Tabassam u Rubab M Suleymanov Department of Physics COMSATS University Institute for Physical Problems Baku State University

In this paper, we describe a study of charged particle yield as a function of pTfor k*（892）0and ?（1020） mesons in proton–proton（pp） and Pb–Pb collisions at ■=?2.76 Te V in the central rapidity region of |y|llisions and in a pT range of 0?-1 in Pb-Pb collisions. We also investigated a very important ratio,the nuclear modification factor, to study the effects of the medium in the most central region, i.e.0%–5% centrality. For data simulation, we used the EPOS-lHC and EPOS-1.99 models. To check the validity of these models' simulations, we compared the data obtained from these Monte Carlo simulation programs with AlICE experimental data for ■=?2.76 Te V. It was concluded that the models' predictions for the ?-meson in pp and for the most central Pb-Pb collisions disagreed with the AlICE data, and that the difference increased with pT. This may be connected with the essential role of collective parton behaviors which could not have been taken into account by the models. For k*0mesons, both programs gave almost the same predictions,and with pTin the interval pT?>?3 Ge V c-1, the predictions were very close to the experimental data. Both models gave higher predictions for the soft pTinterval and lower predictions for the hard interactions. The values of the RAAdistributions were lower than unity and both models were very close to the AlICE data. It is very interesting that the models were not able to describe the pTdistributions, but they gave good predictions for their ratios. This may possibly be due to parton collective behaviors. We observed some additional suppression of k*0at low values of pT with respect to f-mesons, which may be related to the role of the masses of the particles in soft interactions. The rising trend for RAAin the region from pT=?10 Ge V c-1to 20 Ge V c-1observed by the AlICE experiment was absent for the f-mesons.

关键词： Quark Gluon Plasma EPOS-lHC nuclear modification factor

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Bio-amelioration of alkali soils through agroforestry systems in central Indo-Gangetic plains of India

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Journal of Forestry Research 2014年第4期25卷 887-896页

作者： y.P.Singh Gurbachan Singh D.k.Sharma Central Soil Salinity Research Institute Regional Research StationLucknow (U.P.) 226005 India Indian Council of Agricultural Research New Delhi 110001 India Central Soil Salinity Research Institute Karnal Haryana 132001 India

A long-term field study was initiated during 1995 at Central Soil Salinity Research Institute, Regional Research Station, lucknow （26047＇58＂ N and 80°46＇24＂ E） to analyze the effect of agroforestry systems on amelioration of alkali soils. Three agroforestry systems （pas- toral, silvipastoral and silvicultural） were compared with the control where no agroforestry system was introduced. Tree-based silvicultural and silvipastoral systems were characterized by tree species Prosopis juliflora and Acacia nilotica along with grass species leptochloafusca, Panicum maximum, Trifolium alexandrium and Chloris gayana. Growth of ten-year-old Prosopis juliflora and Acacia nilotica planted in combi- nation with grasses was significantly higher over the silviculture system with the same species. Tree biomass yields of P. juliflora （77.20 t·ha-1） and A. nilotica （63.20 t·ha-1） planted under silvipastoral system were significantly higher than the sole plantation of （64.50 t·ha-1 and 52.75 t·ha-1）. Fodder yield under the pastoral system was significantly higher than the silvipastoral system during initial years but it was at par with that of silvipastoral systems after eight years of plantation. The microbial biomass carbon in the soils of silvipastoral systems was significantly higher than in soils under sole plantation of trees and control systems. The Prosopis-based silvipastoral system proved more effective in reduc- ing soil pH, displacing Na＋ from the exchange complex, increasing or- ganic carbon and available N, P and k. Improvement in soil physical properties such as bulk density, porosity, soil moisture and infiltration rate was higher in the Prosopis-based silvipastoral system than in the silviculture system or control On the basis of biomass production and improvement in soil health due to tree ＋ grass systems, silvipastoral agroforestry system could be adopted for sustainable reclamation ofhighly alkali soils.

关键词： agroforcstry systems alkali soils biomass production mi-crobial biomass soil amelioration

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高技术企业间数字鸿沟对协同创新的影响

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科技进步与对策 2017年第1期34卷 75-82页

作者：刘骏刘媛媛俞立平贵州财经大学管理科学学院，贵州贵阳 550025

当今世界正迈入数字时代,大数据、云计算、"互联网+"等技术和发展理念已渗透到企业创新活动中。高技术企业作为创新主体,其协同创新的推进已经越来越受到企业间数字鸿沟的阻碍。从网络建设、网络环境、网络利用、网络人才4个维度构建了... 详细信息

当今世界正迈入数字时代,大数据、云计算、"互联网+"等技术和发展理念已渗透到企业创新活动中。高技术企业作为创新主体,其协同创新的推进已经越来越受到企业间数字鸿沟的阻碍。从网络建设、网络环境、网络利用、网络人才4个维度构建了一套测度指标体系,运用问卷调查法获取数据,定量测度了高技术企业间数字鸿沟。在此基础上,采用结构方程模型分析了企业间数字鸿沟对协同创新的影响途径。结果表明,数字鸿沟可以通过管理方式、战略目标、合作投入、团队分工、学习-吸收能力5条途径影响高技术企业间的协同创新。其中最主要的影响途径是管理方式,其次是战略目标,然后才是合作投入、团队分工、学习-吸收能力。

关键词：高技术企业数字鸿沟协同创新结构方程模型

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MECHANICAl PROPERTIES OF lONGITuDINAl SuBMERGED ARC WElDED STEEl PIPES uSED FOR GAS PIPElINE OF OFFSHORE OIl

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Acta Metallurgica Sinica(English letters) 2008年第2期21卷 85-93页

作者： Z.Z. yang W. Tian Q.R. Ma y.l. li J.k. li J.Z. Gao H.B. Zhang y.H. yang Tubular Goods Research Center of CNPC Xi＇an 710065 China Xiran Aerotechnical College Xi＇an 710077 China

Since the development of offshore oil and gas, increased submarine oil and gas pipelines were installed. All the early steel pipes of submarine pipelines depended on importing because of the strict requirements of comprehensive properties, such as, anti-corrosion, resistance to pressure and so on. To research and develop domes- tic steel pipes used for the submarine pipeline, the longitudinal-seam Submerged Arc Welded （lSAW） pipes were made of steel plates cut from leveled hot rolled coils by both the JCOE and uOE （the forming process in which the plate like the letter “J”, “C”, “0” or “u” shape, then expansion） forming processes. Furthermore, the mechanical properties of the pipe base metal and weld metal were tested, and the results were in accordance with the corresponding pipe specification API SPEC 5l or DNV- OS-FI01, which showed that domestic lSAW pipes could be used for submarine oil and gas pipelines.

关键词： Mechanical properties Offshore oil and gas longitudinal-seamsubmerged arc welded pipe (lSA W) Pipeline JCOE formingprocess uOE forming process

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Simultaneous enhancement of mechanical and shape memory properties by heat-treatment homogenization of Ti_(2)Ni precipitates in TiNi shape memory alloy fabricated by selective laser melting

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Journal of Materials Science & Technology 2022年第6期101卷 205-216页

作者： H.Z.lu l.H.liu C.yang X.luo C.H.Song Z.Wang J.Wang y.D.Su y.F.Ding l.C.Zhang y.y.li National Engineering Research Center of Near-net-shape Forming for Metallic Materials South China University of TechnologyGuangzhou 510640China Musculoskeletal Oncology Department Sun Yat-Sen University Cancer CenterGuangzhouGuangdong ProvinceChina Shenyang Aircraft Design and Research Institute Shenyang 110035China Guangdong Huayi Plumbing Fittings Industry Co. Ltd.Kaiping 529321China School of Engineering Edith Cowan University270 Joondalup DriveJoondalupPerthWA 6027Australia

The excellent shape memory and mechanical properties of Ti Ni shape memory alloys(SMAs) fabricated using selective laser melting(SlM) are highly desirable for a wide range of critical applications. In this study, we examined the simultaneous enhancement of mechanical and shape memory properties using heat-treatment homogenization of Ti_(2)Ni precipitates in a Ti_(50.6)Ni_(49.4)SMA fabricated using SlM. Specifically, because of the complete solution treatment, nanoscale spherical Ti_(2)Ni precipitates were homogeneously dispersed throughout the grain interior. Interestingly, the resultant SMA exhibited an ultrahigh tensile strength of 880 ± 13 MPa, a large elongation of 22.4 ± 0.4%, and an excellent shape memory effect, with a recovery rate of > 98% and ultrahigh recoverable strain of 5.32% after ten loading–unloading cycles. These simultaneously enhanced properties are considerably superior than those of most previously reported Ti Ni SMAs fabricated using additive manufacturing. Fundamentally, the enhancement in tensile strength is ascribed to precipitation strengthening and work hardening, and the large plasticity is mainly attributed to the homogeneous nanoscale globular Ti_(2)Ni precipitates, which effectively impeded the rapid propagation of microcracks. Furthermore, the enhanced shape memory properties are derived from the suppression of dislocation movement and formation of retained stabilized martensite by the presence of high-density dislocations, nanoscale Ti_(2)Ni precipitates, and abundant interfaces. The obtained results provide insight into the enhancement of the two types of properties in Ti Ni SMAs and will accelerate the wider application of SMAs.

关键词： Shape memory alloy Selective laser melting Heat treatment Mechanical properties Shape memory properties

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Sparse Approximations of the Schur Complement for Parallel Algebraic Hybrid Solvers in 3D

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Numerical Mathematics(Theory,Methods and Applications) 2010年第3期3卷 276-294页

作者： l.Giraud A.Haidar y.Saad Joint INRIA-CERFACS lab-42 AV.Coriolis 31057ToulouseFrance Department of Computer Science University of TennesseeKnoxvilleTN37996USA. Department of Computer Science and Engineering University of MinnesotaMinneapolisMN55455USA

In this paper we study the computational performance of variants of an algebraic additive Schwarz preconditioner for the Schur complement for the solution of large sparse linear *** earlier works,the local Schur complements were computed exactly using a sparse direct *** robustness of the preconditioner comes at the price of this memory and time intensive computation that is the main bottleneck of the approach for tackling huge *** this work we investigate the use of sparse approximation of the dense local Schur *** approximations are computed using a partial incomplete lu *** a numerical calculation is the core of the multi-level incomplete factorization such as the one implemented in pARMS. The numerical and computing performance of the new numerical scheme is illustrated on a set of large 3D convection-diffusion problems;preliminary experiments on linear systems arising from structural mechanics are also reported.

关键词： Hybrid direct/iterative solver domain decomposition incomplete/partial factorization Schur approximation scalable preconditioner convection-diffusion large 3D problems parallelscientific computing High Performance Computing.

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Near Earth Vortices Driving of Field Aligned Currents Based on Magnetosphere Multiscale and Swarm Observations

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空间科学学报 2019年第1期39卷 9-17页

作者： ZHANG C SHEN C yANG y y DuNlOP M W TI S RuSSEll C T lüHR H BuRCH J l lINDQVIST P A TORBERT R B FRIIS-CHRISTENSEN E State key laboratory of Space Weather National Space Science Center College of Earth Science University of Chinese Academy of Sciences College of Science Harbin Institute of Technology Institute of China Seismological Bureau Crustal Stress Space Science Institute School of Astronautics Beihang University Rutherford Appleton laboratory university of California German Research Center For Geosciences German Research Center for Geosciences Southwest Research Institute Royal Institute of Technology university of New Hampshire Danish National Space Center

A long-standing mystery in the study of Field-Aligned Currents(FACs) has been that: how the currents are generated and why they appear to be much stronger at high altitudes than in the ionosphere. Here we present two events of magnetotail FACs observed by the Magnetospheric Multiscale Spacecraft(MMS) on 1 st July and 14 th July 2016, to show how the Substorm Current Wedges(SCW) were formed. The results show that particles were transferred heading towards the Earth during the expansion phase of *** azimuthal flow formed clockwise(counter-clockwise) vortex-like motion, and then generated downward(upward) FACs on the tailward/poleward side of the distorted field with opposite vorticity on their Earthward/equatorward side. We also analyzed the Region 1 FACs observed by the Earth Explorer Swarm spacecraft on 1 st July 2016 and found that they were associated with FACs observed by MMS, although differing by a factor of 10. This difference suggests that either there was the closure of the currents at altitudes above 500 km or the currents were not strictly parallel to B and closed at longitudes away from where they were generated.

关键词： Substorm current wedge Magnetosphere Field-aligned currents Flow vorticity Multiple spacecraft measurements

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Improved mechanical properties and strengthening mechanism with the altered precipitate orientation in magnesium alloys

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Journal of Magnesium and Alloys 2022年第5期10卷 1256-1267页

作者： y.J.Wan y.Zeng y.C.Dou D.C.Hu X.y.Qian Q.Zeng k.X.Sun G.F.Quan key laboratory of Advanced Technologies of Materials Ministry of EducationSchool of Material Science and EngineeringSouthwest Jiaotong UniversityChengdu 610031China College of Materials Science and Engineering Sichuan University of Science and EngineeringZigong 643000China Department of Materials The University of ManchesterOxford RoadManchester M139PLUnited Kingdom

Aging prior to twinning deformation was proposed to alter the precipitate orientation of the plate-shapedβ-MgAlfrom(0002)basal planes(named basal plates)to■prismatic planes(named prismatic plates)in AZ31 Mg *** experimental results showed that the compressive yield strength(CyS)of the sample containing prismatic plates increased 40 MPa and the compression ratio raised by 22%compared to that containing basal *** underlying strengthening mechanism was analyzed via a yield strengthen(yS)model with a function of grain size,precipitate characters(size,oritention,fraction)and Schmid factor(SF).It revealed that the improvement of CyS was mainly attributed to the altered precipitate orientation and refined grain size produced by twinning ***,the prismatic plates always have a stronger hardening effect on basal slip than basal plates under the same varites of precipitate diameter and ***,the decreased CRSS ratio of prismatic slip to basal slip revealed that the activity of non-basal slip in Mg alloy might be *** activated slip systems provided more mobile dislocations,contributing to the large compression ratio of the Mg rolled sheet with prismatic plates.

关键词： Precipitate orientation Precipitation strengthening Grain boundary strengthening yield strength model

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Effect of post weld artificial aging and water cooling on microstructure and mechanical properties of friction stir welded 2198-T8 Al-li joints

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Journal of Materials Science & Technology 2022年第28期123卷 92-112页

作者： y.Tao Z.Zhang P.Xue D.R.Ni B.l.Xiao Z.y.Ma Institute of Metal Research Chinese Academy of SciencesShenyang 110016China

Friction stir welding(FSW)under both air cooling and water cooling conditions with welding parameters of 800-1200 rpm rotation rates and 50-200 mm/min welding speeds was carried out on 2198-T8 Al-li alloys,and post weld artificial aging was performed on the air cooled *** welding defects other than lazy S were observed in the nugget zone(NZ)for all *** air cooling condition,the lowest hardness zone(lHZ)occurred in the heat affected zone(HAZ).FSW resulted in gradual dissolution of original T_(1),θ′andδ′/β′from the base material(BM)to the thermo-mechanically affected zone(TMAZ),and complete dissolution of all precipitates in the NZ withδ′/β′and Guinier-Preston zones precipitating during *** air cooled joints exhibited no noticeable changes in intrinsic tensile strength with a joint strength reaching 81.3%of the BM,but varied elongation with welding parameters,which was closely related to failure in the NZ and fracture along lazy *** weld artificial aging led to the largest hardness recovery in the TMAZ but smaller hardness recovery in the initial lHZ and the *** aging kinetics across the joint was determined by volume fraction of both original precipitate dissolu-tion during welding and coarse particles formed during aging,and by dislocation density inherited from *** weld artificial aging greatly enhanced the joint strength with the ultimate tensile strength reaching 87.3%of the *** compared to air cooling condition,water cooling hardly affected the NZ hardness and did not improve the joint strength,and the reason was discussed in light of precipitates,hardness changes and fracture behavior.

关键词： Friction stir welding Aluminum-lithium alloys Microstructure Mechanical properties

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