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Microstructure,mechanical property and corrosion behavior of porous Ti-Ta-Nb-zr

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bioactive Materials 2020年第3期5卷 564-568页

作者： b.Q.Li R.z.Xie X.Lu Mechanics Institute Jinzhong UniversityJinzhong030619China Liaoning Key Materials Laboratory for Railway School of Materials Science and EngineeringDalian Jiaotong UniversityDalian116028China

In this paper,biomedical porous Ti-Nb-Ta-zr with 40%porosity and 166±21μm macro-pore size was successfully fabricated by space holder *** microstructure,Vickers hardness,compressive and electrochemistry behavior were *** results that a few second phases exist inβmatrix of the porous *** Young's modulus is 0.8 GPa,close to 0.01-3 GPa for trabecular *** total recovery strain ratio and pseudoelastic strain ratio are 8.8%and 2.7%,*** fails mainly by brittle cleavage with the fan-shaped and smooth cleaved ***,local ductile fracture by a few dimples and a small amount of transcrystalline fracture with the cleavage of similarly oriented laths in a colony are observed on the fracture *** impedance spectrum of porous Ti-Nb-Ta-zr has the characteristics of half capacitive arc resistance,showing good corrosion resistance in SbF solution.

关键词： Porous Ti-Nb-Ta-zr alloy Macro-pore structure Compressive property Electrochemistry behavior

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工程电磁学

工程电磁学

High mechanical strengths and ductility of stainless steel 304L fabricated using selective laser melting

1976年

作者： popovic b.D. 刘达度译

来源：汇雅图书（南通市图书馆... 评论

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汇雅图书（南通市图书馆）

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Journal of Materials Science & Technology 2019年第2期35卷 388-394页

作者： Q.b.Nguyen z.zhu F.L.Ng b.W.Chua S.M.L.Nai J.Wei Singapore Institute of Manufacturing Technology Institute of Research and Development Duy Tan University

Achieving not only high mechanical strengths but also high ductility is recently established using an additive manufacturing technique called selective laser melting. In the present study, stainless steel 304 L fully dense samples were successfully printed using the 3 D systems – ProX 300 printing machine. The ductility and tensile yield strength were almost two and three times higher compared to those of ASTM cast's alloy. Honey comb like nano-cellular structure with different orientation was observed in the fine grains(~4μm) due to fast cooling rate. In addition, the formation of martensite phase in random grains is also a contributor to the strengths. Furthermore, negative residual stresses in the build and horizontal directions were detected and assisted further increase in the tensile strength. Fractography revealed the ductile feature of plastic deformation and the crack openings at unmelted particles or pores.

关键词： Additive manufacturing Stainless steel Powder Selective laser melting

Microstructural Evolution and Mechanical behavior of Friction-Stir-Welded DP1180 Advanced Ultrahigh Strength Steel

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Acta Metallurgica Sinica(English Letters) 2020年第1期33卷 58-66页

作者： z.W.Wang G.M.Xie D.Wang H.zhang D.R.Ni P.Xue b.L.Xiao z.Y.Ma Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819China

Friction stir lap welding of a DP1180 advanced ultrahigh strength steel was successfully carried out by using three welding tools with different pin lengths. The effects of the welding heat input and material flow on the microstructure evolution of the joints were analyzed in detail. The relationship between pin length and mechanical properties of lap joints was studied. The results showed that the peak temperatures of all joints exceeded A c3, and martensite phases with similar morphologies were formed in the stir zones. These martensite retained good toughness due to the self-tempering effect. The formation of ferrite and tempered martensite was the main reason for the hardness reduction in heat-affected zone. The mechanical properties of the lap joints were determined by loading mode, features of lap interface and the joint defects. When the stir pin was inserted into the lower sheet with a depth of 0.4 mm, the lap joint exhibited the maximum tensile strength of 12.4 kN.

关键词： Advanced ultrahigh strength steel Friction stir welding Microstructure Mechanical behavior

Grain refinement of Mg-alloys by native MgO particles: An overview

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Journal of Magnesium and Alloys 2022年第11期10卷 2919-2945页

作者： z.Fan F.Gao Y.Wang S.H.Wang J.b.Patel brunel Centre for Advanced Solidification Technology(bCAST) Brunel University LondonUxbridgeUB83PHUK

A fine and equiaxed solidification process delivers multidimensional benefits to Mg-alloys, such as improved castability, reduced casting defects, enhanced mechanical properties, increased corrosion resistance and potential for increased recycled contents. Despite extensive research on grain refinement of Mg-alloys in the last few decades, currently, there is no effective grain refiner available for refining Mg-Al alloys, and our current understanding of grain refining mechanisms is not adequate to facilitate the development of effective grain *** the EPSRC(UK) Li ME Hub’s research program, substantial advances have been made in understanding the early stages of solidification covering prenucleation, heterogeneous nucleation, grain initiation and grain refinement. In this paper, we provide a comprehensive overview of grain refinement of Mg-alloys by native MgO particles. We show that native MgO particles can be made available for effective grain refinement of Mg-alloys by intensive melt shearing regardless of the alloy compositions. More importantly, we demonstrate that(1) the addition of more potent exogenous particles will not be more effective than native MgO;and(2) MgO particles are difficult to be made more impotent for grain refinement through promoting explosive grain initiation. We suggest that the most effective approach to grain refinement of Mg-alloys is to make more native MgO particles available for grain refinement through dispersion, such as by intensive melt shearing.

关键词： Mg-alloys Grain refinement Magnesia(MgO) Nucleation Grain initiation

Releases of phosphate fertilizer industry in the surrounding environment:Investigation on heavy metals and polonium-210 in soil

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Journal of Environmental Sciences 2010年第9期22卷 1387-1397页

作者： M.Aoun A.G.El Samrani b.S.Lartiges V.Kazpard z.Saad Lebanese Atomic Energy Commission Lebanese University Faculty of SciencesPlatform for Research and Analysis in Environmental Sciences Nancy University-LEM-ENSG/INPL-CNRS-15 Av.du Charmois

Distribution of Cu, zn, Pb, Cr, Ni, Mn concentrations and the activity of polonium-210 in the surrounding area of a phosphate fertilizer industry located on the eastern coast of the Mediterranean Sea has been determined. Nineteen sampling sites were distributed around the industrial zone on a surface area of about 100,000 m^2. Atomic absorption spectroscopy and Alpha spectroscopy were used to quantify the heavy elements and polonium-210, respectively. Investigation on a particle scale was conducted by TEM and SEM coupled to EDX and X-ray cartography to determine the nature of heavy elements carriers and their distribution. Heavy elements were mainly concentrated inside the particle size fraction 〈 50 μm. Their levels decreased with distance increasing from the industry. According to the reference soil, enrichment factors were about 10, 15, 32 and 100 times for zn, Pb, Cu, and Cr, respectively inside the particle size fraction 〈 50 μm on the closest sites to the industry. The main contaminant sources were transport and storage of row materials and the free release of phosphogypsum waste. Heavy elements were entrapped inside agglomerates of sulfates, phosphates and iron oxihydroxides in a diffused shape. Polonium-210 with an enrichment factor of about 56, showed the same behavior of the spatial distribution of the trace elements.

关键词： heavy elements phosphogypsum fortilizer industry polonium-210 Alpha spectrometry

Effects of effective stress and temperature on permeability of sandstone from CO2-plume geothermal reservoir

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Journal of Rock Mechanics and Geotechnical Engineering 2016年第6期8卷 819-827页

作者： Y.z.Sun L.z.Xie b.He C.Gao J.Wang College of Architecture and Environment Sichuan UniversityChengdu610065China MOE Key Laboratory of Energy Engineering Safety and Disaster Mechanics Sichuan UniversityChengdu610065China Institute of New Energy and Low-Carbon Technology Sichuan UniversityChengdu610065China State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resources and HydropowerSichuan UniversityChengdu610065China

Rock is generally complex and heterogeneous,therefore the heterogeneity effects of effective stress and temperature on permeability should be taken into *** this study,two-part Hooke’s model（TPHM） is introduced to understand the influences of effective stress and temperature on permeability of soft and hard parts（two parts） of rock based on coupling thermo-hydro-mechanical *** a fixed temperature level（25 ℃.35 ℃.50 ℃.65 ℃.80 ℃.90 ℃ and 95 ℃）.the tests were carried out in a conventional triaxial system whereas the confining pressure was remained at 50 *** the pore pressure was increased to the specified levels step by step.i.e.8 MPa,18 MPa.28 MPa.38 MPa.41 MPa,44 MPa.46 MPa and 48 *** temperature-dependent relationships for two parts permeabilities are proposed on the basis of the initial test *** point out that temperature of 65 ℃-90 ℃ is the threshold for the development of CO2-plume geothermal（CPC） reservoir sandstone cracking under low effective stress（2-9 MPa） based on the relationship between temperature and soft part ***,we discuss the effect of temperature on the two parts in the *** results indicate that as the temperature increases from 25 ℃ to 65 ℃.the flow channel in the hard part has a stronger response to temperature than that in the soft part at a fixed effective stress level,which is opposite to the situation of effective *** that natural rock is generally heterogeneous with non-uniform pore structure,we suggest a physical interpretation of the phenomenon that before the thermal cracking threshold the two parts have different responses to temperature.

关键词： Sandstone from CO2-plume geothermal (CPG) reservoir Temperature and effective stress Flow channel Two parts permeabilities

MICROSTRUCTURE TRANSFORMATION IN THE WELDING HEAT AFFECTED zONE OF 800MPa GRADE ULTRA FINE STRUCTURED STEEL

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Acta Metallurgica Sinica(English Letters) 2004年第3期17卷 238-246页

作者： J.b. Liu L.J. Hu Y.T.Wang z. Q. Liu K. Miao z.L. Tian Huazhong University of Science and Technology Wuhan 430074 China Technology Center of Wuhan Iron and Steel (Group) Corporation Wuhan 430080 China Central Iron and Steel Research Institute Beijing 100080 China

The transformation behavior and microstructure development in the heat affected zone(HAz)of 800MPa grade ultra fine structured steel was *** was found that the HAz has intermediate temperature transformation characteristics in a wide range of cooling rates,with the bainite sheaves consisting of bainite ferrite plates without carbide precipitation and retained austenite in the fast cooling *** relatively high cooling rates,which corresponded to low heat inputs,the hardness of the simulated HAz was above that of the base *** the cooling rate was below 9C/s,the welding HAz would have an obvious *** analysis of transformation rates in continuous cooling processes was completed by numerical differential *** result indicated that the microstructure transformation rate of the HAz in 800MPa grade ultra fine structured steel changed sharply to slow speeds when the cooling time t8/5 is longer than 7s.

关键词： ultra fine structured steel weld heat affected zone transformation rate microstructure

Impacts of forest management on liana diversity and community structure in a tropical forest in Ghana:implications for conservation

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Journal of Forestry Research 2016年第1期27卷 147-153页

作者： P.Addo-Fordjour z.b.Rahmad A.M.S Shahrul M.Ashyraf School of biological Sciences Universiti Sains Malaysia Department of Theoretical and Applied biology College of Science Kwame Nkrumah University of Science and Technology (KNUST) The Centre for Marine and Coastal Studies (CEMACS) Universiti Sains Malaysia

We studied the impacts of liana cutting as a forest management tool on liana diversity （species richness, Shannon diversity index） and community structure （diam- eter distribution, basal area, species dominance） in the Asenanyo Forest Reserve, Ghana. Two types of silvicul- turally treated forests were studied： Logging treated （LT） and Tropical Shelterwood System （TSS） treated forests. An untreated primary forest was included as a control, result- ing in three forest management systems. Lianas with diameter 〉2 cm were identified in ten 40 × 40 m2 plots within each management system. Liana cutting signifi- cantly reduced liana species richness, Shannon diversity index, and basal area in the LT forest after two decades. However, liana species richness and basal area werecomparable in the TSS treated and untreated forests, indi- cating significant recovery in the former after over six decades. Sφrensen similarity index of liana species com- position between the untreated forest and each of the treated forests was moderate. Our findings suggest that liana cutting most likely influenced the dominance of some liana species. In view of the adverse impact of blanket liana cutting on liana diversity, selective liana cutting is rec- ommended as a means of controlling liana numbers while maintaining liana diversity.

关键词： Forest management system Liana diversity Liana basal area Silviculture Tropical forest biodiversity