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Correlation between Porosity and Fracture Mechanism in high Pressure Die Casting of AM60B Alloy

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Journal of Materials Science & Technology 2016年第1期32卷 54-61页

作者： x.li S.M.xiong Z.Guo School of Materials Science and Engineering Tsinghua University State key Laboratory of Automobile Safety and Energy Tsinghua University

x-ray tomography was used to characterize the porosity in high pressure die casting of AM60B alloy. In situ tensile deformation was performed to observe the change of porosities and their influences on crack initiation, propagation and subsequent fracture of specimen. Results showed that four types of porosi- ties, including gas-shrinkage pore, gas pore, net-shrinkage and island-shrinkage, could be identified according to the formation mechanism and morphology characterization. During tensile deformation, it was shown that the gas-shrinkage pore and net-shrinkage, rather than gas pore or island-shrinkage, were the main sources for crack initiation. In addition, the crack propagated by interconnecting the po- rosities at the cross section with minimum efficient force bearing area. At these locations where externally solidified crystals （ESCs） were present, the crack would propagate along the ESC boundaries in an inter- granular mode, while at these locations without ESCs, the crack would propagate roughly along the direction perpendicular to the tensile stress in a combination of trans-granular and inter-granular modes.

关键词： high pressures die casting AM60B alloy Fracture mechanism Porosity

In Vitro Evaluation of the Feasibility of Commercial Zn Alloys as Biodegradable Metals

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Journal of Materials Science & Technology 2016年第9期32卷 909-918页

作者： C.wang h.T.Yang x.li Y.F.Zheng Department of Interventional Radiology and Vascular Surgery Peking University Third Hospital Department of Materials Science and Engineering College of Engineering Peking University

In this work, three widely used commercial Zn alloys （ZA4-1, ZA4-3, ZA6-1 ） were purchased and pre- pared by hot extrusion at 200℃. The microstructure, mechanical properties, corrosion behaviors, biocompatibility and hemocompatibility of Zn alloys were studied with pure Zn as control, Commercial Zn alloys demonstrated increased strength and superb elongation compared with pure Zn. Accelerated corrosion rates and uniform corrosion morphologies were observed in terms of commercial Zn alloys due to galvanic effects between Zn matrix and α-Al phases. 100% extracts of ZA4-1 and ZA6-1 alloys showed mild cytotoxicity while 50% extracts of all samples displayed good biocompatibility. Retardant cell cycle and inhibited stress fibers expression were observed induced by high concentration of Zn^2＋ releasing during corrosion. The hemolysis ratios of Zn alloys were lower than 1% while the adhered platelets showed slightly activated morphologies. In general, commercial Zn alloys possess promising mechanical properties, appropriate corrosion rates, significantly improved biocompatibility and good hemocompatibility in comparison to pure Zn. It is feasible to develop biodegradable metals based on commercial Zn alloys.

关键词： Commercial Zn alloys Biodegradable metals Mechanical properties Corrosion behaviors Cytotoxicity hemocompatibility

hierarchical structure and deformation behavior of a novel multicomponent β titanium alloy with ultrahigh strength

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Journal of Materials Science & Technology 2022年第12期107卷 227-242页

作者： x.li x.N.wang k.liu G.h.Cao M.B.li Z.S.Zhu S.J.wu School of Materials Science and Engineering Beihang UniversityBeijing 100191China Titanium Alloys Laboratory Beijing Institute of Aeronautical MaterialBeijing 100095China School of Materials Science and Engineering Shanghai UniversityShanghai 200444China

Based on the general [Mo] equivalent criterion and d-electron orbital theory, a new ultrahigh-strength βtitanium alloy with eight major elements(Ti-4.5Al-6.5Mo-2Cr-2.6Nb-2Zr-2Sn-1V, TB17) for industrial applications was developed. An ingot of five tons was successfully melted by thrice vacuum consumable arc melting. The microstructure and elements partitioning of different conditions were investigated systematically. The results suggest that the hierarchical structures of micro-scale first α phase(αf), nano-scale secondary α phase(αs), and ultrafine FCC substructures can be tailored by solution plus aging(STA) heat treatment. The lateral and epitaxial growth of αfphase promotes the hCP-α to FCC substructure transformation with the help of elements partitioning during the aging process. Moreover, the element V, generally regarded as β stabilizer, is found to mainly concentrate in the Al-rich αfphase in this study probably due to its relatively lower content and the strong bonding energy of Al-V. The hierarchical structure has a strong interaction with dislocations, which contributes to achieve a superhigh strength of 1376 *** addition, the plastic strain is partitioned in the multi-scale precipitates(such as the α and FCC substructures) and β matrix, resulting in a considerable plasticity. TEM observation demonstrates that high density entangled dislocations at interfaces and mechanical twins exist in the STA sample after tensile test. It can be deduced that both dislocation slipping and twinning mechanisms are present in this ***, TB17 alloy can serve as an excellent candidate for structural materials on aircrafts that require high strength and lightweight.

关键词： Titanium alloy hierarchical structure Deformation behavior Ultrahigh strength Elements partitioning

China’s International Education Initiatives and View of Its Role in Global Governance

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Frontiers of Education in China 2012年第1期7卷 103-123页

作者： Sharon x.li Ontario Institute for Studies in Education University of TorontoToronto ON M5S 1V6Canada

China is becoming an increasingly important actor in global *** paper contends that China participates by promoting its own global governance concepts on the one hand and by complying with the established global norms on the *** paper introduces several key global governance concepts of the Chinese government and argues that they are likely to persist due to their roots in traditional Chinese Daoist and Confucian *** then focuses on China’s initiatives in education-the creation of Confucius Institutes and China’s involvement in United Nations(UN)educational initiatives-as examples of the Chinese ***,the paper discusses China’s educational profile in relation to its broader role in global governance.

关键词： global governance international education initiatives global norms China

Enhanced strength and ductility of Mg-Gd-Y-Zr alloys by secondary extrusion

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Journal of Magnesium and Alloys 2013年第1期1卷 54-63页

作者： x.li w.Qi k.Zheng N.Zhou Guangzhou Research Institute of Non-ferrous Metals Guangzhou 510651China

The Mg-12Gd-3Y-0.6Zr(Gw123,wt.%)alloy was prepared by cast,and thermo-mechanically treated by single and secondary hot extrusion *** microstructure,texture and mechanical properties of the extruded alloy were *** results show that in different treated conditions the microstructure is mainly composed ofα-Mg solid solution and second phases of Mg_(3)Y_(3)Gd_(2) and Mg_(5)(GdY)*** best mechanical properties are achieved in the secondary extruded alloy after ageing,with the ultimate tensile strength(UTS),tensile yield strength(TYS)and elongation(ɛ)being 446 MPa,350 MPa and 10.2%at room temperature.A weak texture aligned with〈101¯0〉||ED(extrusion direction)component and spread from〈101¯0〉to〈112¯0〉poles was obtained in secondary extrusion,which is caused by the occurrence of dynamic recrystallization(DRx)in shear bands for texture *** fracture modes in extruded Gw123 alloy are mixed pattern of transgranular and intergranular fracture,as well as cleavage *** strengthening mechanisms were quantitatively analysed from the different aspects using the measured microstructural *** grain boundaries and solid solution strengthening were the main contributors to the high tensile strength of the Gw123 alloy.

关键词： Mg-Gd-Y-Zr magnesium alloy Microstructure Texture Mechanical properties Rare earth Dynamic recrystallization

Targeting TRPM2- and TRPM4-extrasynaptic N-methyl-D-aspartate receptor coupling in ischemic stroke

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Neural Regeneration Research 2023年第11期18卷 2383-2384页

作者： Pengyu Zong Cindy x.li Jianlin Feng lixia Yue Department of Cell Biology Calhoun Cardiology CenterUConn HealthFarmingtonCTUSA

Ischemic stroke represents a heavy burden on public ***,recanalization is the only effective therapy for ischemic stroke in a small population of eligible ***,there is no effective adjunct medication for preventing neuron loss after reperfusion to mitigate longlasting brain *** N-methyl-Daspartate receptors (esNMDARs) are the major cause of ischemic neuronal ***,there is no inhibitor selectively ta rgeting esNMDARs without compromising the function of other"beneficial"syna ptic NMDARs.

关键词： aspartate ischemic medication

Breeding Rice lines for physio-functional food through indica‘Zhaxima’×japonica‘Nanjing 46’haploid technique

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Food Production, Processing and Nutrition 2019年第1期1卷 23-34页

作者： Q.Q.Tian x.li C.M.Lu x.w.Fang Institute of Food Crops Jiangsu Academy of Agricultural SciencesJiangsu High Quality Rice R&D CenterNanjing BranchChina National Center for Rice ImprovementNanjing 210014China Jiangsu Collaborative Innovation Center for Modern Crop Production Yangzhou 225009China College of life Science Nanjing Normal UniversityNanjing 210023China

Resistant starch(RS)encompasses those forms of starch which are not accessible to human digestive enzymes and are fermented in the colons producing short chain fatty *** plant materials containing RS are few in the *** this contribution,the culture ability of callus from anthers of F1 plants from,landraces,‘Zhaxima’(Oryza sativa ***,high-RS rice line with 7.705±0.142,g/100 g)×‘Nanjing 46’(Oryza sativa ***,rice variety with RS content(g/100 g)of 0.200±0.001 crosses were studied for obtaining high RS rice *** results showed that when M8 basic induction medium was added with 1.5 mg/L 2,4-D、2 mg/LNAA and 0.3 mg/L kT,the inductivity of callus was high as 32.14%for 21 d after pretreatment at 4°C for 3 d;when MS differentiation basic medium was added with 2 mg/LkT and 3 mg/L ABA,the frequency of regeneration for callus was 50.3%with only a regeneration frequency of 4.55%grown into green *** RS content in the seeds was between those of the two parents and was partially normally distributed,the highest RS contents of the regenerated plants was as high as 7.66±1.197%.This produced an efficient technology for regenerating stable rice lines with high RS and good eating quality using anthers culture.

关键词： Rice(Oryza sativa L.) anther culture regeneration resistant Starch

Performance evaluation of polyamide reverse osmosis membranes incorporated silica nanoparticles for concentrating peach juice:An invitro evaluation

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Food Bioscience 2022年第4期48卷 646-656页

作者： x.li Fuping Zheng R.Mohammadi M.h.Jazebizadeh D.Semiromi School of Marine and Biological Engineering Yancheng Teachers UniversityJiangsu224007China Beijing Laboratory of Food Quality and Safety Beijing Technology and Business UniversityBeijing100048China Department of Chemical Engineering Shiraz BranchIslamic Azad UniversityShirazIran Department of Mechanical Engineering Khomeinishahr BranchIslamic Azad UniversityKhomeinishahrIran

In this study,a mixture of water and peach juice is used as feed for the reverse osmosis(RO)*** sheet,polyester sulfone polymer and polyamide from interfacial polymerization of m-phenylenediamine(MPD)and trimesoyl chloride(TMC)monomers with silica nanoparticles are used to produce the membrane.A solution of Poly(ether sulfone)(PES)is prepared in N-Methyl-2-pyrrolidone(NMP)solvent with 10 wt%,15 wt%,and 20 wt%and the addition of 0.5 wt%,1.5 wt%,and 3 wt%of silica *** electron microscope(SEM)and Fourier transform infrared(FTIR)analysis are used to evaluate the morphology and functional groups of the prepared *** to the SEM images,it is observed that the membrane consists of three layers and the polyamide layer(surface)of the membrane,is responsible for the main separation is dense hills and valleys’surface *** polyester sulfone layer(middle)has finger-shaped porosity and the obtained results of the contact angle test show that with increasing silica nanoparticles,the membrane becomes more hydrophilic and the angle decreases as the polyester sulfone layer(middle)have finger-shaped *** bonds formed in the resulting membrane structure were identified,including sulfonylide,polyamide,and silica *** results of the contact angle test show that as the silica nanoparticle increases,the membrane became more hydrophilic and the angle was *** sample with 3%nanoparticles has the lowest angle and the highest level of hydrophilicity,followed by the membrane 151.5,which has 1.5%nanoparticles,and then the membrane 150 without nanoparticles.

关键词： Reverse osmosis Concentration Membrane Silica nanoparticles Polyamide

Influence of alloy element partitioning on strength of primary α phase in Ti-6Al-4V alloy

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Journal of Materials Science & Technology 2018年第5期34卷 782-787页

作者： L.R.Zeng h.L.Chen x.li L.M.Lei G.P.Zhang Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China University of Chinese Academy of Sciences Beijing 100049 China School of Materials Science and Engineering University of Science and Technology of China Shenyang 110016 China AVIC Commercial Aircraft Engine Co.LTD Shanghai 200241 China

The partitioning effect of Al（α-phase stabilizer） and V elements（β-phase stabilizer） on strength of the primary α phases in the α/β Ti-6 Al-4 V alloy with the bimodal microstructure was *** was found that partitioning of Al and V elements took place in the Ti-6 Al-4 V alloy during the recrystallization process,leading to the variation of the content of Al and V elements in the primary α phases with changing the volume fraction of the primary α *** tests reveal a general trend that the strength of the primary α phases increases with decreasing the volume fraction of the primary α phases,and such trend is independent on the loading direction relative to the c-axis of the α *** enhanced strength is attributed to the increase of the content of Al element in the primary α phase,but it is not dominated evidently by the change of the V *** solid solution strengthening contributed from both the elastic strain introduced by the solute atoms and the variation of the density of states was estimated theoretically.

关键词： Ti-6Al-4V Nanoindentation Strength Alloy element partitioning Crystallographic orientation