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comparison of microstructure and mechanical behavior of Ti-35Nb manufactured by laser powder bed fusion from elemental powder mixture and prealloyed powder

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Journal of Materials Science & Technology 2022年第10期105卷 1-16页

作者： J.c.Wang Y.J.liu S.X.liang Y.S.zhang l.Q.Wang T.B.Sercombe l.c.zhang School of Engineering Edith Cowan University270 Joondalup DriveJoondalupPerthWA 6027Australia School of Engineering M050The University of Western Australia35 Stirling HighwayCrawleyPerthWA 6009Australia Northwest Institute for Nonferrous Metal Research Xi’an 710016China State Key laboratory of Metal Matrix composites School of Material Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Although different types of powder feedstock are used for additive manufacturing via laser powder bed fusion(l-PBF),limited work has attempted to directly compare the microstructure and mechanical behavior of components manufactured from those powder feedstock.This work investigated the microstructure,phase composition,melt pool morphology,and mechanical properties of a prealloyed Ti-35Nb alloy manufactured using l-PBF and compared these to their counterparts produced from elemental powder mixture.The samples manufactured from the powder mixture are composed of randomly distributed undissolved Nb in theα/βmatrix,resulting from the unstable melt pool during the melting of the powder mixture.By contrast,parts produced from prealloyed powder display a homogeneous microstructure withβandαphases,owing to the full melting of prealloyed powder,therefore,a more stable melt pool to achieve a homogeneous microstructure.The Ti-35Nb manufactured from prealloyed powder exhibits large tensile ductility(about 10 times that of the counterparts using mixed powder),attributed to the high homogeneity in microstructure and chemical composition,strong interface bonding,relatively low oxygen content,and the existence of a large amount ofβphase.This work sheds insights into understanding the effect of powder feedstock on the melt pool stability therefore the microstructure and mechanical behavior of the resultant parts.

关键词： Titanium-niobium Powder bed fusion Additive manufacturing Melt pool stability Microstructure Mechanical properties

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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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Mechanistic modeling of copper corrosions in data center environments

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Building Simulation 2024年第3期17卷 483-492页

作者： Rui zhang Jianshun zhang Roger Schmidt Jeremy l.Gilbert Department of Mechanical and Aerospace Engineering College of Engineering and Computer ScienceSyracuse UniversitySyracuseNY13244USA Buildings and Transportation Science Division Oak Ridge National LaboratoryOak RidgeTN37830USA SyracusecoE-New York center of Excellence in Environmental and Energy Systems Syracuse University727 E.Washington StreetSyracuseNY13244USA Department of Bioengineering Clemson UniversityClemson-Medical University of South Carolina Bioengineering ProgramCharlestonSC29425USA

Air-side economizers are increasingly used to take advantage of“free-cooling”in data centers with the intent of reducing the carbon footprint of buildings.However,they can introduce outdoor pollutants to indoor environment of data centers and cause corrosion damage to the information technology equipment.To evaluate the reliability of information technology equipment under various thermal and air-pollution conditions,a mechanistic model based on multi-ion transport and chemical reactions was developed.The model was used to predict cu corrosion caused by cl_(2)-containing pollutant mixtures.It also accounted for the effects of temperature(25℃and 28℃),relative humidity(50%,75%,and 95%),and synergism.It also identified higher air temperature as a corrosion barrier and higher relative humidity as a corrosion accelerator,which agreed well with the experimental results.The average root mean square error of the prediction was 13.7Å.The model can be used to evaluate the thermal guideline for data centers design and operation when cl_(2)is present based on pre-established acceptable risk of corrosion in data centers’environment.

关键词： chloride pollutant mixture copper corrosion model data center temperature relative humidity synergistic effect

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MIcROSTRUcTURAl STABIlITY OF lAMEllAR TiAl BASED AllOYS AT HIGH TEMPERATURES

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中国有色金属学会会刊:英文版 1999年第S1期9卷 45-54页

作者： G.l.chen l.c.zhang W.J.zhang State Key laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China laboratory of Atomic Imaging of Solids Institute of Metal ResearchChinese Academy of SciencesShenyang 110015China

The microstructural stability of lamellar TiAl base alloys at high temperatures was studied by conventional and high resolution transmission electron microscopy. The influence of substructures on the thermal stability of lamellar structure was emphasized. These substructures produced by thermal mechanical treatments include the interfacial dislocations and ledges, the subgrain boundaries, the impinged T(Q) twins and misorientated lamellar interfaces. The microstructural change of three kinds of lamellar TiAl base alloys containing differents type and densities of substructures were compared during exposure at 800~1 000 ℃. It was found that the existence of such substructures could accelerate the degeneration of lamellar structure, leading to the rapid necking and break up of α 2 plates, the coarsening of γ plates, and the formation of new γ grains. As a result, the lamellar structure with substructures started to degenerate after thermal exposure at 800℃ for 4.5 h. While only slight coarsening was observed at the colony boundaries in the lamellar structure without substructures even after exposure at 900 ℃ for 7 d.

关键词： microstructural stablility lamellar Ti-Al based alloys thermal exposure

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Material flow analysis and global warming potential assessment of an industrial insect-based bioconversion plant using housefly larvae

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Journal of Environmental Sciences 2024年第5期139卷 483-495页

作者： Tao lu Fan lü Nanlin liao Honghui chai Hua zhang Pinjing He Institute of Waste Treatment and Reclamation Tongji UniversityShanghai 200092China State Key laboratory of Pollution control and Source Reuse Tongji UniversityShanghai 200092China Zhejiang Qihe Ecological Technology co. Ltd.Hangzhou 310052China

The significant increase in the demand for biomass waste treatment after garbage classification has led to housefly larvae treatment becoming an attractive treatment option.It can provide a source of protein while treating biomass waste,which means that nutrients can be returned to the natural food chain.However,the performance of this technology in terms of its environmental impacts is still unclear,particularly with regards to global warming potential(GWP).This study used a life cycle assessment(lcA)approach to assess a housefly larvae treatment plant with a treatment capacity of 50 tons of biomass waste per day.The lcA results showed that the 95% confidence intervals for the GWP in summer and winter were determined to be 24.46-32.81 kg cO_(2) equivalent(cO_(2)-eq)/ton biomass waste and5.37-10.08 kg cO_(2)-eq/ton biomass waste,respectively.The greater GWP value in summer is due to the longer ventilation time and higher ventilation intensity in summer,which consumes more power.The main GWP contributions are from(1)electricity needs(accounting for 78.6% of emissions in summer and 70.2%in winter)and(2)product substitution by mature housefly larvae and compost(both summer and winter accounting for 96.8% of carbon reduction).

关键词： Biomass waste Musca domestica Housefly larvae life cycle assessment Global warming potential

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Experimental clearance rate and intraguild predation of jellyfish cyanea nozakii

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Journal of Oceanology and limnology 2024年第1期42卷 128-140页

作者： Pengpeng WANG Fang zhang Song SUN Shuguo lÜ cAS Key laboratory of Marine Ecology and Environmental Sciences Institute of OceanologyChinese Academy of SciencesQingdao 266071China laboratory for Marine Ecology and Environmental Sciences Pilot National Laboratory for Marine Science and Technology(Qingdao)Qingdao 266237China University of chinese Academy of Sciences Beijing 100049China Jiaozhou Bay Marine Ecosystem Research Station Chinese Academy of SciencesQingdao 266071China center for Ocean Mega-Science Chinese Academy of SciencesQingdao 266071China Institute of Marine Ecology and Environment Hainan Academy of Environmental SciencesHaikou 570100China

cyanea nozakii,a common jellyfish distributed in offshore china,has a complex trophic relationship with other zooplankton groups.However,few studies have reported the predation rates and prey selection patterns of c.nozakii medusae on different prey items.Research is also lacking on the intraguild predation of Aurelia coerulea(another common bloom jellyfish in offshore china)by c.nozakii.To address the knowledge gaps,the clearance rates of c.nozakii for different prey items,including copepods(smalllarge>1000μm),fish larvae,and gelatinous prey(hydromedusae,A.coerulea ephyrae,and chaetognaths),were measured.The influence of predator size on the clearance rate was also determined.Additionally,we examined the intraguild predation of c.nozakii on A.coerulea medusae.The clearance rates of c.nozakii varied widely with prey organisms,being independent of prey concentrations.Gelatinous organisms,except for chaetognaths,were captured with considerably high efficiency,followed by fish larvae and copepods,indicating the preferential prey selection of gelatinous organisms by c.nozakii.The clearance rate increased linearly with the cross-sectional area of c.nozakii.Body size in medusae may,to some extents,underpin their capacity to capture more prey by increasing the encounter rate and capture success through ontogeny.c.nozakii preyed voraciously on A.coerulea in high feeding efficiency,but the clearance rate decreased with increasing A.coerulea(as prey)size.This phenomenon of intraguild predation suggests a speculative hypothesis of potential population regulation of A.coerulea by c.nozakii.The information regarding the feeding ecology of c.nozakii reported in this study is important for understanding plankton dynamics in marine ecosystems with extensive occurrences of this jellyfish.

关键词： Scyphomedusae predation rate gelatinous organisms prey selection feeding mechanism

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High-efficiency carbonation Modification Methods of Recycled coarse Aggregates

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Journal of Wuhan University of Technology(Materials Science) 2024年第2期39卷 386-398页

作者：张美香 YANG Xiaolin 丁亚红 SUN Bo zhang Xianggang lÜXiuwen Department of civil Engineering Henan Polytechnic UniversityJiaozuo 454150China college of Architectural Engineering Xinyu UniversityXinyu 336500China

To solve the problem of only surface carbonation and realize high-efficiency carbonation of recycled coarse aggregate,the method of carbonated recycled coarse aggregate with nano materials pre-soaking was first put forward.The carbonation effect of modified recycled coarse aggregate with three different carbonation methods was evaluated,and water absorption,apparent density and crush index of modified recycled coarse aggregate were measured.combined with XRD,SEM,and MIP microscopic analysis,the high-efficiency carbonation strengthening mechanism of modified recycled coarse aggregate was revealed.The experimental results show that,compared with the non-carbonated recycled coarse aggregate,the physical and microscopic properties of carbonated recycled coarse aggregate are improved.The method of carbonation with nano-SiO_(2) pre-soaking can realize the high-efficiency carbonation of recycled coarse aggregate,for modified recycled coarse aggregate with the method,water absorption is reduced by 23.03%,porosity is reduced by 44.06%,and the average pore diameter is 21.82 nm.The high-efficiency carbonation strengthening mechanism show that the pre-socked nano-SiO_(2) is bound to the hydration product ca(OH)_(2) of the old mortar with nano-scale c-S-H,which can improve the cO_(2) absorption rate,accelerate the carbonation reaction,generate more stable cacO_(3) and nano-scale silica gel,and bond to the dense three-dimensional network structure to realize the bidirectional enhancement of nano-materials and pressurized carbonation.It is concluded that the method of carbonation with nano-SiO_(2) pre-soaking is a novel high-efficiency carbonation modification of recycled coarse aggregate.

关键词： recycled coarse aggregate pressurized carbonation high-efficiency carbonation nano-SiO2 strengthening mechanism

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control Policy learning Design for Vehicle Urban Positioning via BeiDou Navigation

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Journal of Systems Science & complexity 2024年第1期37卷 114-135页

作者： QIN Yahang zhang chengye cHEN ci XIE Shengli lEWIS Frank l School of Automation Guangdong University of TechnologyGuangzhou 510006China Guangdong Key laboratory of IoT Information Technology Guangzhou 510006China. center for Intelligent Batch Manufacturing Based on IoT Technology Key laboratory of Intelligent Detection and The Internet of Things in Manufacturing Ministry of EducationGuangzhou 510006China Guangdong-HongKong-Macao Joint laboratory for Smart Discrete Manufacturing Guangzhou 510006China Key laboratory of Intelligent Information Processing and System Integration of IoT Ministry of EducationGuangzhou 510006China. UTA Research Institute The University of Texas at ArlingtonFort WorthTX 76019USA

This paper presents a learning-based control policy design for point-to-point vehicle positioning in the urban environment via BeiDou navigation.While navigating in urban canyons,the multipath effect is a kind of interference that causes the navigation signal to drift and thus imposes severe impacts on vehicle localization due to the reflection and diffraction of the BeiDou signal.Here,the authors formulated the navigation control system with unknown vehicle dynamics into an optimal control-seeking problem through a linear discrete-time system,and the point-to-point localization control is modeled and handled by leveraging off-policy reinforcement learning for feedback control.The proposed learning-based design guarantees optimality with prescribed performance and also stabilizes the closed-loop navigation system,without the full knowledge of the vehicle dynamics.It is seen that the proposed method can withstand the impact of the multipath effect while satisfying the prescribed convergence rate.A case study demonstrates that the proposed algorithms effectively drive the vehicle to a desired setpoint under the multipath effect introduced by actual experiments of BeiDou navigation in the urban environment.

关键词： BeiDou navigation multipath effect prescribed convergence rate reinforcement learning urban localization.

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The preface: Interplay of topological and magnetic orders in the Mn-Bi-Te family

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National Science Review 2024年第2期11卷 6-7页

作者： Fu-chun zhang Hai-Zhou lu X.c.Xie Kavli Institute for Theoretical Sciences University of Chinese Academy of Sciences Department of Physics Southern University of Science and Technology (SUSTech) International center for Quantum Materials School of Physics Peking University

The discovery and synthesis of MnBi2Te4in 2013 initially garnered little attention [1]. Yet, the revelation of its topological properties in 2019 [2–6] sparked a surge of research into the MnBiTe family. These extensive studies are primarily driven by two objectives:the realization of a high-temperature quantum anomalous Hall effect （QAHE） and the exploration of exotic phases born from the interplay of topological and magnetic orders,

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Effect of radiative loss mechanisms on FIR thermometric parameters of Nd3+-doped lithium tellurite glasses

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Journal of Rare Earths 2024年第7期42卷 1250-1257页

作者： c.Y.Morassuti A.P.l Silva l.A.O.Nunes S.M.lima l.H.c.Andrade Optical and Photothermal Spectroscopy Group (GEOF) Center for Studies in Natural Resources (CERNA)State University of Mato Grosso do Sul(UEMS) Renato Archer Information Technology center Institute of Physics of Sao carlos University of S?o Paulo

Nd3+-doped tellurite glasses are promising materials for thermometers based on the fluorescence intensity ratio（FIR） technique.Nevertheless,at high Nd3+concentrations,energy transfer（ET） processes such as optical reabsorption and cross-relaxation can affect the Nd3+emission,which has been little explored in the literature.Therefore,the present work investigated the use of Nd3+-doped tellurite glass(samples doped with Nd3+at 0.2 mol%,0.5 mol%,2.0 mol%,and 4.0 mol%) in fluorescence thermometers,in the temperature range from 299 to 371 K.The results indicate a strong dependence of the FIR parameters on the Nd3+concentration,due to changes in the emission band profiles caused by optical reabsorption of the Nd3+emissions and cross-relaxation processes.A decrease of the relative sensitivity of the ratio4F5/2→4I9/2/4F3/2→4I9/2is observed for samples doped with higher amounts of Nd3+.The maximum relative sensitivity at 299 K is 3.00%/K,which is the highest value among the reported Nd3+ions.

关键词： Fluorescence intensity ratio Judd-Ofelt Nd3+-doped tellurite glass Optical thermometry Rare earths

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