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Study of Microstructure and Magnetic Properties of Pr-Fe-B-Cu Permanent Magnets by Hot Deformation

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Journal of Rare Earths 2002年第3期20卷 188-192页

作者：陈秀云姜忠良高天明吴严杨昌平朱静 Dept. of Mater. Sci. and eng. Sch. of Mater. Sci. and Eng. Tsinghua Univ. Beijing 100084 China

The relationship between the microstructures and magnetic properties of rare earth cast permanent Pr Fe B Cu alloys by hot deformation was studied. Fine and well aligned column grains can be obtained by using a proper solidification mould with a high cooling rate. The soft magnetic phase α Fe can be removed during proper annealing treatment. Hot pressing can produce the anisotropy and refine the grain size, so that the magnetic properties are greatly improved. The technique has the advantages of simple processing, low cost and high benefit, compared with the common sintering processing. Under the condition of the deformation temperature of 1073 K, 90% strain and strain rate of 40×10 -3 s -1 , the magnetic properties obtained are: B r=1.05 T, i H c=955 kA·m -1 , ( BH ) max =207 kJ·m -3 .

关键词： rare earths hot deformation anisotropy sintering

Effects of Alloying Elements on Microstructure and Erosion Resistance of Fe-C-Cr Weld Surfacing Layer

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Journal of materials Science & Technology 2003年第4期19卷 351-354页

作者： Daqian SUN, Wenquan WANG, Zhaozhi XUAN, Yue XU and Zhenfeng.ZHOUsch.ol of materials Science and eng.neering, Jilin University, Changchun 130025, China sch. of Mat. Sci. and eng. Jilin Univ. Changchun 130025 China

Effects of alloying elements on microstructure and erosion resistance of Fe-C-Cr weld surfacing layer have been studied. The experimental results show that increasing C and Cr content favors improving the erosion resistance of the layer, and the excessive C and Cr result in decreasing the erosion resistance at 90 deg. erosion. That Mo, Nb or Ti improves the erosion resistance of Fe-C-Cr weld surfacing layer is mainly attributed to increasing the amount of M7C3 and forming fine NbC or TiC in austenite matrix, but the excessive Mo, Nb or Ti is unfavorable. The addition of Mo, Nb and Ti in proper combination possesses stronger effect on improving the erosion resistance and the erosion resistance (εA) of Fe-C-Cr weld surfacing layer with fine NbC, TiC and M7C3 distributing uniformly in austenite matrix obviously increases to 2.81 at 15 deg. erosion and 2.88 at 90 deg. erosion when the layer composition is 3.05C, 20.58Cr, 1.88Mo, 2.00Nb and 1.05Ti (in wt pct).

关键词： Weld surfacing layer Alloying elements Erosion resistance

Diffusive healing of internal fatigue micro-cracks in pure titanium

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中国有色金属学会会刊：英文版 2001年第5期11卷 675-680页

作者：杨君刚孙军张海龙 sch. of Mat. Sci. and eng. Xi'an Jiaotong Univ. Xi'an 710049 China

The internal micro cracks with the critical leng.h about 30?μm and thickness less than 1?μm were introduced into the pure titanium samples by uniaxial tension compression low cycle fatigue method. The experimental results indicate that the internal fatigue micro crack clearly evolves from the original penny shaped crack into a string of spherical voids in the longitudinal section plane of the fatigue sample after the vacuum diffusive healing at the high temperature. The quantitative relationship between the radius and the spacing of spherical voids depends on the crack position (within grains, on grain boundaries or transgranular sites) and its orientations within the grain. The diffusive healing, the related thermodynamics and mechanism, and the effect of the surface tension anisotropy on the relationship between void diameter and void spacing are also discussed.

关键词： pure titanium internal fatigue micro crack diffusive healing

Evaluation on Fracture Toughness at Dynamic Loading for Welded Joint Based on the Local Approach

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Journal of materials Science & Technology 2004年第1期20卷 113-117页

作者： Hongyang JING, Lianyong XU, Lixing HUO and Yufeng.ZHANGsch.ol of materials Science and eng.neering, Tianjin University, Tianjin 300072, China sch. of Mat. Sci. and eng. Tianjin Univ. Tianjin 300072 China

The changes in mechanical properties and fracture toughness by dynamic loading were investigated with experiments. The parameter R, which can reflect the effect of the loading rate and the temperature rising during the high loading rate, could be employed to describe the constituent relation for the typical structure steel and its weld metal. The dynamic loading effect on the stress/strain fields and the temperature variation in the vicinity of the crack tip was analyzed by the finite element method, the dynamic fracture behavior was evaluated based on the local approach. It has been found that the Weibull stress is an effective fracture parameter, independent of the temperature and the loading rate.

关键词： Fracture toughness Dynamic loading Welded joint

Effect of HD Process on Microstructure and Hard Magnetic Properties of NdFeAlB Magnet

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Journal of Rare Earths 2002年第3期20卷 193-196页

作者：姜忠良陈秀云陈晓东石大立杨昌平朱静 sch. of Mater. Sci. and eng. Tsinghua Univ. Beijing 100084 China

The effect of Hydrogen Decrepitation (HD) process on the magnetic properties and microstructure of sintered NdFeAlB magnet (HD magnet) was investigated. The results show that the coercivity of HD magnet is higher than that of traditional ball milling (BM) magnet, while the remanence and the maximum energy product of HD magnet are lower. Microstructure analysis shows that some fine un sintered powders are distributed at the grain boundaries of HD magnet. X ray diffraction (XRD) analysis reveals that the degree of easy axis alignment of HD magnet is lower. Some ideas to improve the current HD process were proposed.

关键词： rare earths hydrogen decrepitation NdFeB permanent magnet

Formation and Characterization of Bone-like Nanoscale Hydroxyapatite in Glass Bone Cement

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Journal of materials Science & Technology 2004年第6期20卷 772-774页

作者： Qiang FU, Nai ZHOU, Wenhai HUANG, Deping WANG and Liying ZHANGsch.ol of materials Science and eng.neering, Tongji University, Shanghai 200092, China sch. of Mat. Sci. and eng. Tongji Univ. Shanghai 200092 China

Glass based bone cement (GBC) was synthesized by mixing CaO-SiO2-P2O5 based glass powder with ammonium phosphate liquid medium. Bone-like hydroxyapatite (HAP, Ca10(PO4)6(OH)2) was found to form after GBC was immersed in simulated body fluid (SBF). HAP crystal grew with an increasing time along c axle and reached about 200 nm in leng.h after 30 days, however, the end plane granularity remained 30-50 nm. The chem.cal composition, crystal structure and morphology of HAP formed from GBC were proved to have great resemblance with living HAP. It is believed that GBC was a desirabie biomedicai material with high bioactivity. Furthermore, the high compressive streng.h guaranteed the possibility of GBC in clinical application.

关键词： Bioactivity Bone cement Hydroxyapatite Microstructure

Luminescent Properties of Porous Si Passivated by Diamond Film and DLC Film

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Journal of materials Science & Technology 2004年第2期20卷 145-148页

作者： Linjun WANG, Yiben XIA, Weili ZHANG, Minglong ZHANG and Weimin SHIsch.ol of materials Science & eng.neering, Shanghai Univ., Shanghai 201800, China sch. of Mat. Sci. and eng. Shanghai Univ. Shanghai 201800 China

Surface passivation methods for porous Si (PS) surfaces, i.e., depositing diamond film or diamond-like carbon (DLC) film on PS surfaces, were attempted. Two emission bands, weak blue band and strong red band existed in the PL spectrum of diamond film coated on PS, were discovered by the photoluminescence measurements. The luminescent mechanism and stability were discussed. The results indicated that diamond film may stabilize the PL waveleng.h and intensity of PS, and therefore could become a promising passivation film of porous Si. The PL properties of PS coated by DLC films, including hydrogenated diamond like carbon (DLC:H) film and nitrogen doped DLC film (DLC:N) were also studied in this paper. The DLC films may stabilize the PL of PS, but the photoluminescent intensity was obviously weaker than that of diamond film coated PS.

关键词： Porous Si Passivation Diamond film Diamond-like carbon film

Deposition of Bioactive Layer on NiTi Alloy by chem.cal Treatment

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Journal of materials Science & Technology 2002年第6期18卷 534-537页

作者： Ya LIU, Xianjin YANG, Minfang CHEN, Sheng.i ZHU and Zhenduo GUIsch.ol of materials Science and eng.neering, Tianjin University, Tianjin 300072, China sch. of Mat. Sci. and eng. Tianjin Univ. Tianjin 300072 China

A simple chem.cal method was developed for inducing bioactivity on NiTi alloys (50 at. pct by Ni/Ti). A layer of calcium phosphate was deposited on the surface to improve biocompatibility of the alloy. NiTi alloys were first etched in HNO3 aqueous solution, and then treated with boiling diluted NaOH solution. A rough surface was created and a thin TiO2 layer was formed on the surface. Pre-calcification was then introduced by immersing the treated NiTi alloys in supersaturated Na2HPO4 solution and supersaturated Ca(OH)2 solution in turn before calcification in simulated body fluid (SBF). A dense and uniform bonelike calcium phosphate (Ca-P) bioactive layer was formed on the surfaces of the specimen, which would improve their biocompatibility. Morphology and element analysis on NiTi surfaces during the treatments were investigated in detail by means of environment scanning electron microscopy (ESEM), energy dispersion X-ray spectroscopy (EDXS), and X-ray diffraction (XRD).

关键词： NiTi alloy chem.cal method Bioactive layer Biocompatibility

Study on the Basic Mechanical Behaviors of High Density Polyethylene Electrofusion Welded Joints at Different Temperature

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Journal of materials Science & Technology 2003年第6期19卷 603-606页

作者： Lixing HUO, Fangjuan QI, Yufeng.ZHANG, Hongyang JING and Xinqi YANGsch.ol of materials Science and eng.neering, Tianjin University, Tianjin 300072, China sch. of Mat. Sci. and eng. Tianjin Univ. Tianjin 300072 China

The basic mechanical behaviors of high density polyethylene electrofusion welded joint at different temperatures were studied by using differently designed specimens in this paper. The results show that the streng.h of weld bonding plane is higher than that of the pipe and socket materials at room temperature. In order to get the shear streng.h of electrofusion welded joint, the effective bond leng.hs were reduced by cutting artificial groove through the socket. The effective bonding leng.h of welded joint to get the shear streng.h is decreased with decreasing testing temperature. The shear streng.h and the sensibility to sharp notch of HDPE material increased with decreasing temperature.

关键词： Basic mechanical behaviors High density polyethylene Electrofusion welded joint