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A study of magnetostriction, spin reorientation, and Mssbauer spectra of Tb_(0.3)Dy_(0.6)Pr_(0.1)(Fe_(1-x)Al_x)1.95 alloys with substitution of Fe by Al

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Science china(Physics,Mechanics & Astronomy) 2010年第3期53卷 449-453页

作者： ZHENG XiaoPing1,3, ZHANG PeiFeng1,2, LI FaShen2 & HAO Yuan2 1 Institute of Electronic Information Science and Technology, lanzhou City university, lanzhou 730070, china 2 key laboratory for magnetism and magnetic materials, ministry of education, lanzhou university, lanzhou 730000, china 3 State key laboratory of Advanced Non-Ferrous materials, Gansu Province, lanzhou university of Technology, lanzhou 730050, china 1. Institute of Electronic Information Science and Technology Lanzhou City University Lanzhou 730070 China3. State Key Laboratory of Advanced Non-Ferrous Materials Gansu Province Lanzhou University of Technology Lanzhou 730050 China2. Key Laboratory for Magnetism and Magnetic Materials Ministry of Education Lanzhou University Lanzhou 730000 China

The effects of Al substitution for Fe on the structure, magnetics, magnetostriction, anisotropy and spin reorientation of a series of Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 alloys (x=0.05, 0.1, 0.15, 0.2, 0.25, 0.3) at room temperature have been investigated. The alloys of Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 substantially retain MgCu2-type C-15 cubic Laves phase structure when x3Dy0.6Pr0.1(Fe1-xAlx)1.95 alloys decreases drastically with increasing x and the giant magnetostrictive effect disappears for x > 0.15. Fortunately, a small amount of Al substitution is beneficial to a decrease in the magnetocrystalline anisotropy. The spin reorientation temperature decreases with increasing x. The analysis of the Mssbauer spectra indicates that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the increase of Al concentration x, namely, spin reorientation, resulting in the change of macroscopical magnetic properties and magnetostriction. The hyperfine field decreases, but the isomer shifts increases with Al concentration increasing and the quadruple splitting QS shows a weak concentration dependence.

关键词： cubic laves phase magnetostriction spin reorientation Mssbauer

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Estimation to the turbulent kinetic energy dissipation rate and bottom shear stress in the tidal bottom boundary layer of the Yellow Sea

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Progress in Natural Science:materials International 2007年第3期17卷 289-297页

作者： LIU Zhiyu and WEI Hao (key laboratory of Physical Oceanography, State education ministry, Ocean university of china, Qingdao 266003, china) key laboratory of Physical Oceanography Ocean University of China Qingdao 266003 China

High frequency velocity fluctuations were measured by using an acoustic Doppler velocimeter (ADV) in the tidal bottom boundary layer (BBL) of the Yellow Sea (YS) for 25 h. The turbulent kinetic energy dissipation rate and the bottom shear stress were estimated and analyzed. Results show that: (1) in the tidal BBL of the YS, the variations of the dissipation rate and the bottom shear stress during 25 hare (1.8×10-8-3.4×10 -5) W·kg-1 and (6.6×10-4-7.5×10-1) N·m - 2 respectively, indicating that there are strong dissipations in the tidal BBL of the YS; (2) in the well-mixed tidal BBL, the turbulence is mainly shear-induced locally and the production and dissipation are generally in equilibrium; (3) for the seas where the semidiurnal tidal current is dominant, both the dissipation rate and the bottom shear stress exhibit a strong quarter-diurnal variation; (4) the mean bottom drag coefficient Cd (0.45) is 0.0017 (corresponding Cd( 1.00) = 0.0015), but it has significant variations (0.0005-0.0082). The mean bottom roughness length is 2.8×10-5 m.

关键词： tidal bottom boundary layer turbulent kinetic energy dissipation rate bottom shear stress ADV the Yellow Sea.

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Simulation of Tensile Behavior of Nickel Foam

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稀有金属材料与工程 2011年第S3期40卷 224-227页

作者： Zhao Mingjuan 1, Zhang Xiaolan 1, Zhao Longzhi 1,3, Zhang Jinsong 2 1 key laboratory of ministry of education for Conveyance and Equipment, East china Jiaotong university, Nanchang 330013, china 2 Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, china 3 key laboratory of Superlight materials & Surface Technology, ministry of education, Harbin Engineering university, Harbin 150001, china E china Jiaotong Univ Key Lab Minist Educ Conveyance & Equipment Nanchang 330013 Peoples R China Harbin Engn Univ Minist Educ Key Lab Supertight Mat & Surface Technol Harbin 150001 Peoples R China Chinese Acad Sci Inst Met Res Shenyang 110016 Peoples R China

Nickel foam is widely used as the electrode, the catalyst carrier, sound absorption material and other application fields. The tensile behavior of the open cell nickel foam which is one of the most important parameters in the design process was investigated with the finite element method based on ANSYS software in this paper. The effects of strain rates and temperature on the yield strength of the nickel foam were obtained. The results show that the yield strength exhibit a nonlinear reduction with the increases of the temperature for the elastic bending of the struts of the reinforcement grew quickly depending on the temperature. However, the yield strength increases slowly with the improvement of the strain rate because the strain rate neither change the internal structure and properties such as the porosity and the aperture, nor alter the external circumstance in order to change the internal properties such as the temperature. The results of the simulation accord with those of the experiments, which is very important to understand the tensile behavior of the foam materials.

关键词： nickel foam ANSYS yield strength temperature strain rate

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Structure, spin reorientation and Mssbauer effect studies of Tb0.3Dy0.7(Fe1-xAlx)1.95 alloys

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Science china(Physics,Mechanics & Astronomy) 2006年第2期Mechanics & Astronomy) .卷 149-157页

作者： ZHENG Xiaoping1,2,4, ZHANG Peifeng1,3, FAN Duowang1, LI Fashen3 & HAO Yuan41. key laboratory of Opto-Electronic Technology and Intelligent Control, ministry of education, lanzhou Jiaotong university, lanzhou 730070, china 2. Institute of Electronic Information Science and Technology,lanzhou Teachers College, lanzhou 730070, china 3. key laboratory for magnetism and magnetic materials, ministry of education, lanzhou university, Lan-zhou 730000, china 4. State key Lab. of Advanced Non-Ferrous materials, Gansu Province, lanzhou university of Technology, lanzhou 730050, china

The effect of Al substitution for Fe on crystal structure, magnetostriction and spontaneous magnetostriction, anisotropy and spin reorientation of a series of polycrys-talline Tb0.3Dy0.7(Fe1?xAlx)1.95 alloys (x = 0, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, 0.35) at room temperature and 77 K was investigated systematically. It was found that the primary phase of Tb0.3Dy0.7(Fe1?xAlx)1.95 is the MgCu2-type cubic Laves phase structure when x 3Dy0.7(Fe1?xAlx)1.95 increases approximately and monotonically with the increase of x. The substitution of Al leads to the fact that the magnetostriction λ inceases slightly in a low magnetic field (H ≤ 40 kA/m), but decreases sharply and is easily close to saturation in a high applied field as x increases, showing that a small amount of Al substitution is beneficial to a decrease in the magnetocrystalline anisotropy. It was also found that the spontaneous magnetostriction λ111 decreases greatly with x in-creasing. The analysis of the M?ssbauer spectra indicated that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the changes of composition and temperature, namely spin reorientation. A small amount of non-magnetic phase exists for x = 0.15 in Tb0.3Dy0.7(Fe1?xAlx)1.95 alloys and the alloys be-come paramagnetic for x > 0.15 at room temperture, but at 77 K the alloys still remain magnetic phase even for x = 0.2. At room temperature and 77 K, the hyperfine field de-creases and the isomer shifts increase with Al concentration increasing.

关键词： magnetostriction cubic Laves phase spin reorientation M?ssbauer.

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Impacts of permafrost changes on alpine ecosystem in Qinghai-Tibet Plateau

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Science china Earth Sciences 2006年第11期49卷 1156-1169页

作者： WANG Genxu1,3 , LI Yuanshou2 , WU Qingbai2 & WANG Yibo3 1. Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, china 2. Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, lanzhou 730000, china 3. Resource and Environment School, lanzhou university, lanzhou 730000, china Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu China Resource and Environment School Lanzhou University Lanzhou China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou China

Alpine cold ecosystem with permafrost environment is quite sensitive to climatic changes and the changes in permafrost can significantly affect the alpine ecosystem. The vegetation coverage, grassland biomass and soil nutrient and texture are selected to indicate the regime of alpine cold ecosystems in the Qinghai-Tibet Plateau. The interactions between alpine ecosystem and permafrost were investigated with the depth of active layer, permafrost thickness and mean annual ground temperature (MAGTs). Based on the statistics model of GPTR for MAGTs and annual air temperatures, an analysis method was developed to analyze the impacts of permafrost changes on the alpine ecosystems. Under the climate change and human engineering activities, the permafrost change and its impacts on alpine ecosystems in the permafrost region between the Kunlun Mountains and the Tanggula Range of Qinghai-Tibet Plateau are studied in this paper. The results showed that the per- mafrost changes have a different influence on different alpine ecosystems. With the increase in the thickness of active layer, the vegetation cover and biomass of the alpine cold meadow exhibit a significant conic reduction, the soil organic matter content of the alpine cold meadow ecosystem shows an exponential decrease, and the surface soil materials become coarse and gravelly. The alpine cold steppe ecosystem, however, seems to have a relatively weak relation to the permafrost environment. Those relationships resulted in the fact that the distribution area of alpine cold meadow decreased by 7.98% and alpine cold swamp decreased by 28.11% under the permafrost environment degradation during recent 15 years. In the future 50 years the alpine cold meadow ecosystems in different geomorphologic units may have different responses to the changes of the permafrost under different climate warming conditions, among them the alpine cold meadow and swamp ecosystem located in the low mountain and plateau area will have a relatively

关键词： permafrost environment, alpine cold ecosystem, statistics relationship, climate change, impacts, Qinghai-Tibet Plateau.

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Crystallization kinetics of (Ni_(0.75)Fe_(0.25)_(78-x)Nb_xSi_(10)B_(12)(x=0,5)amorphous alloys

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Rare Metals 2006年第4期25卷 342-348页

作者： CHEN Xueding WEI Hengdou WANG Xiaojun State key laboratory of Advanced New Non-ferrous materials l.anzhou University of Technology l.anzhou 730050 China

Amorphous ribbons of （Ni0.75Fe0.25）78-xNbxSi10B12 （x = 0, 5） were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of continuous heating, and the activation energies of the alloys were calculated using Kissinger plot method and Ozawa plot method on the basis of differential thermal analysis data. The crystallization products were analyzed by X-ray diffraction. After the （Ni0.75Fe0.25）78Si10B12 amorphous alloy was annealed at the temperatures 715 and 745 K, a single phase of γ-（Fe, Ni） solid solution with grain sizes of about 10.3 and 18.5 nm, respectively, precipitates in the amorphous matrix. The crystallized phases are γ-（Fe, Ni） solid solution, Fe2Si, Ni2Si, and Fe3B after annealing at 765 K. The （Ni0.75Fe0.25）73NbsSi10 B12 amorphous alloy was annealed at 720, 750, and 800 K; and the crystallization phases, γ（Fe, Ni） solid solution, （Fe, Ni）23B6. Ni31Si12 and Nb2NiB0.16 form simultaneously.

关键词： amorphous materials thermal analysis crystallization kinetics activation energy

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Microstructure and Tensile Properties of ZK60 Alloy Fabricated by Simplified Rapid Solidification Powder Metallurgy (S-RS P/M) Process

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Journal of materials Science & Technology 2010年第2期26卷 151-155页

作者： Zhenya Zhang, Huashun Yu , Shaoqing Wang, Haitao Wang and Guanghui Min key laboratory of Liquid Structure and Heredity of materials, ministry of education, Shandong university, Jinan 250061, china key laboratory of Liquid Structure and Heredity of materials Ministry of Education Shandong University Jinan 250061 China

This study investigated the microstructures and mechanical properties of ZK60 alloy prepared by a simplified rapid solidification powder metallurgy （RS P/M） processing system （S-RS P/M）, which consists of warm press in dry air and hot extrusion. Microstructure characterizations showed that S-RS P/M alloy consisted of magnesium matrix and oxide stringers of ~1 #m in width. TEM （transmission electron microscopy） observations illustrated nano-size magnesia particles （10-30 nm） constituted oxide stringer in detail. Due to a relatively higher volume of nano-size magnesia particle produced during S-RS P/M process, 0.2% yield strength of S-RS P/M ZKO0 alloy was found to be as high as 382 MPa, which is 10% higher than that of RS P/M alloy. The improvement in mechanical properties is mainly attributed to the combination effects of Orowan mechanism and coefficient of thermal expansion （CTE） mismatch because of the approximately same average grain size.

关键词： Microstructure Mechanical properties Rapid solidification powder metallurgy Nano-size magnesia

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Effects of surface modification on isothermal oxidation behavior of HVOF-sprayed NiCrA1Y coatings

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Progress in Natural Science:materials International 2011年第2期21卷 173-179页

作者： Li-yong NI,Zi-long WU,Chun-gen ZHOU key laboratory of Aerospace materials and Performance(ministry of education), Department of materials Science and Engineering,Beihang university,Beijing 100191,china key laboratory of Aerospace materials and Performance (ministry of education) Department of Materials Science and Engineering Beihang University Beijing 100191 China

NiCrAlY coatings were deposited on Ni-based superalloy by high-velocity oxygen-fuel spraying(HVOF).Surface modification by means of grit-blasted,shot-peened and ground methods was used in order to study the effect of surface conditions on the isothermal oxidation behavior of HVOF-sprayed NiCrAlY coatings at 1 050℃.The results showed that surface modification had an obvious effect on the isothermal oxidation behavior of the *** was a large decrease in growth rate compared with the as-sprayed *** scale formed on the grit-blasted and shot-peened coatings was a mixture of Al2O3and NiCr2O4,while the oxide formed on the ground coating was composed mainly of *** surface modification,the content of NiCr2O4spinels decreased compared with the as-sprayed coating.

关键词： NiCrAlY HVOF isothermal oxidation thermal barrier coating

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Microstructures and corrosion properties of casting in situ Al_3Ti-Al composites

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Rare Metals 2010年第1期29卷 78-85页

作者： CHEN Tijun LI Jian HAO Yuan Gansu key laboratory of Advanced Nonferrous materials Lanzhou University of Technology Lanzhou 730050 China School of Material Science and Engineering Xi＇an Shiyou University Xi ＇an 710065 China

The effects of Ti content and the alloying elements of Si and Cu on the microstructures of casting in situ Al3Ti-Al composites were investigated. Simultaneously, their corrosion properties were also discussed. The results indicate that the aspect ratios of Al3Ti platelets in different Al based composites are different although all of them are in flaky shape. The morphologies of Al3Ti phase are not only determined by Ti content, but are also related to the alloying elements. The grain refining role of Al3Ti phase in the pure Al and Al-Cu based composites is more effective than that in the Al-Si based composite. The addition of Ti decreases the corrosion resistance of pure Al and Al alloys. The corrosion resistances of the composites are dependent on both the corrosion characteristics of the corresponding matrixes and the distribution of Al3Ti platelets.

关键词： metal matrix composite microstructure corrosion resistance alloying element morphology

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Effects of solidification parameters on microstructure and mechanical properties of continuous columnar-grained Cu-Al-Ni alloy

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Progress in Natural Science:materials International 2011年第5期21卷 368-374页

作者： Zhen WANG,Xue-feng LIU,Jian-xin XIE key laboratory for Advanced materials Processing,ministry of education, university of Science and Technology Beijing,Beijing 100083,china key laboratory for Advanced materials Processing Ministry of Education University of Science and Technology Beijing Beijing 100083 China

Effects of melt temperature and casting speed on microstructure and mechanical properties of Cu-14%Al-3.8%Ni(mass fraction) alloy wires fabricated by continuous unidirectional solidification technology were *** was found that the average size of columnar grain in the alloy decreased and grain boundary turned clear and straight with increasing the casting speed at a given melt *** the melt temperature was up to 1 280℃,theβ1phase gradually transformed into lozenged and lanciformγ’1martensite,as well as parallel-sided plateβ’*** alloy with numerous coarsely dendriticγ2phase has poor mechanical properties due to the difficulty of stress-induced martensitic *** the amount of theγ2phase reduced and the coarse dendriteγ2phase evolved into the fine square particles,the elongation of the alloy increased gradually with a decrease in tensile ***,the plasticity of the alloy could also be improved by increasing the amount and size of martensites,particularly the lanciformγ’*** the alloy was almost composed of coarse lanciformγ’1martensite,the tensile strength and elongation of the alloy could be up to 772 MPa and 18.9%,respectively,and the tensile curve consisted of three transformation platforms.

关键词： shape memory alloy continuous unidirectional solidification columnar grain martensitic transformation

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