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Journal of Rare Earths 2002年第4期20卷 291-294页

作者：赵研辉李艳丽姚枚杨庆祥 coll. of mat. sci. and eng. Yanshan Univ. Qinhuangdao 066004 China

The modifying effect of rare earth (RE) oxide on inclusions in hardfacing metals of medium-high carbon steel was investigated by means of thermodynamics. The thermodynamic analysis for inclusion format.on shows that RE oxide can be reduced to RE element by carbon, then the RE element can react with oxygen and sulfur to form the RE oxide, RE sulfide and RE oxide-sulfide in hardfacing molten pool. The deoxidization and the desulphurization can be carried out and the liquid metal can be purified. In addition, RE oxide can also react with sulfur to form RE oxide-sulfide directly. Therefore, the harmful effect of sulfur can be decreased.

关键词： rare earths oxide inclusion hardfacing metal thermodynamics

Entrapment of Inclusions in Diamond Crystals Grown from Fe-Ni-C System

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Journal of mat.rials sci.nce & Technology 2002年第2期18卷 171-172页

作者： Yuxian LIU, Limei XIAO and Longwei YINcoll.ge of mat.rials sci.nce and eng.neering, Shandong University, Jinan 250061, China [ Manuscript received June 28, 2001, in revised form October 18, 2001] coll. of mat. sci. and eng. Shandong Univ. Jinan 250061 China

Diamond single crystals grown from Fe-Ni-C system at high temperature-high pressure (HPHT) usually contain inclusions related to the metallic catalyst. During the diamond growth, the metallic inclusions are trapped by the growth front or are formed through reaction between the contaminants trapped in the diamond. In the present paper, the metallic inclusions related to the catalyst were systemat.cally examined by transmission electron microscopy (TEM). The chemical composition and crystal structure of the metallic inclusions were for the first time determined by selected area electron diffraction pattern (SADP) combined with energy dispersive X-ray spectrometry (EDS). It is shown that the inclusions are mainly composed of orthorhombic FeSi2, fcc (FeNi)23C6, and orthorhombic Fe3C, hexagonal Ni3C.

关键词： Synthetic diamond Fe-Ni-C system Inclusion Transmission electron microscopy

Effect of Nb on the Interfacial Wettability in Al_2O_3/Medium Mn Steel

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Journal of mat.rials sci.nce & Technology 2003年第6期19卷 625-627页

作者： Sirong YU, Yaohui LIU and Zhenming HEcoll.ge of mat.rials sci.nce and eng.neering, Jilin University, Changchun 130025, China coll. of mat. sci. and eng. Jilin Univ. Changchun 130025 China

To develop medium Mn steel (MMS) mat.ix composites reinforced by AI2O3 particles, the effect of Nb on the interfacial wettability of AI2O3/MMS and its mechanism were investigated in this paper. The results show that the wetting angle of the specimens with different Nb contents are bigger than that of the specimen without Nb at the first stage, and then decreases with time at 1450℃. At certain time, the wetting angle is lower than that of the specimen without Nb. At 1550 and 1600℃, the wetting angle of the specimens containing Nb decreases quickly with time at first stage. After 10 min, the wetting angle reaches a steady state, and hardly changes with time. The mechanisms of Nb to improve the wettability can be attributed to the enrichment of Nb at the interface and Nb serves as surface active agent of MMS at T1550℃, and reduces the interfacial energies.

关键词： Madium Mn steel A12O3 Nb Wettalility

Electroless Plating of Ni-Fe-P Alloy and Corrosion Resistance of the Deposit

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Journal of mat.rials sci.nce & Technology 2005年第1期21卷 39-42页

作者： Senlin WANGcoll.ge of mat.rials sci.nce and eng.neering, Huaqiao University, Quanzhou 362021, ChinaAssoc. Prof., Ph.D., coll. of mat. sci. and eng. Huaqiao Univ. Quanzhou 362021 China

Electroless Ni-Fe-P alloys in an alkaline bath were plated. The effects of deposition parameters on the plating rate and the coating composition were examined. The weight loss test and the anodic polarization measurement of the deposits in 3.5 wt pct NaCI solution (pH7.0) showed that the deposits with the mole ratio of NiS04/FeSO4 being 0.07:0.03, pH8.0 and 7.5 possess better corrosion resistance than that of the other deposits and the Ni-Fe-P deposits did not form passive films in this environment. In 5.0 wt pct NaOH solution, the Ni-Fe-P deposits have better corrosion resistance and formed passive films.

关键词： Nickel Iron Electroless deposition Anodic polarization

Characterization of ZnO Based Varistor Derived from Nano ZnO Powders and Ultrafine Dopants

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Journal of mat.rials sci.nce & Technology 2005年第2期21卷 183-186页

作者： Weizhong YANG, Dali ZHOU, Guangfu YIN, Runsheng.WANG and Yun ZHANG coll.ge of mat.rial sci.nce and eng.neering, Sichuan University, Cheng.u 610064, China coll. of mat. sci. and eng. Sichuan Univ. Chengdu 610064 China

Nanosized ZnO powders were prepared with a two-step precipitation method. The average size of ZnO particles was about 80 nm and their size distribution was narrow. Combining with ultrafine additive powders, ZnO base varistor was produced via an oxide mixing route. ZnO varistor derived from normal reagent grade starting mat.rials was investigated for comparison purpose. Outstanding microstructure of the ZnO varistor derived from nanosize ZnO powders and ultrafine dopants was obtained: uniform distribution of fine ZnO grains (less than 3 microns), grain boundary and the dopant position. Higher varistor voltage (U=492 V/mm) and nonlinear coefficient (α=56.2) as well as lower leakage current (TL=1.5 μuA) were achieved. The better electrical properties were attributed to the uniform microstructure, which in turn led to stable and uniform potential barriers. Also this improved technique is more feasible for producing ZnO nanopowders and resulting varistor in large scales.

关键词： Zinc oxide (ZnO) Varistor Nanopowders Ultrafine dopants Two-step precipitation

Vacancies and Antisites in B2 FeAl and DO_3 Fe_3Al with a Modified Analytic EAM Model

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Journal of mat.rials sci.nce & Technology 2001年第6期17卷 601-604页

作者： Xiaolin SHU, Wan gyu HU, Hanning XIAO and Huiqiu Deng.coll.ge of mat.rials sci.nce and eng.neering, Hunan University, Changsha 410082, China Ban gwei ZHANG International Centre of mat.rials Physics, Chinese Academy of sci.nces, S coll. of mat. sci. and eng. Hunan Univ. Changsha 410082 China

A simple modified analytic EAM model for bcc Fe and fcc Al was used to calculate the lattice constant and elastic constants of B2 FeAl and DO3 Fe3Al alloys. The format.on energies of ... 详细信息

A simple modified analytic EAM model for bcc Fe and fcc Al was used to calculate the lattice constant and elastic constants of B2 FeAl and DO3 Fe3Al alloys. The format.on energies of vacancy and antisite were also calculated. The present calculations are in agreement with the experimental data and the theoretical results obtained by other authors.

关键词： Al DO Fe Vacancies and Antisites in B2 FeAl and DO3 Fe3Al with a Modified Analytic EAM Model EAM

New Developed Welding Electrode for Improving the Fatigue Streng.h of Welded Joints

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Journal of mat.rials sci.nce & Technology 2002年第6期18卷 527-531页

作者： Wenxian WANG, Lixing HUO, Yufeng.ZHANG, Dongpo WANG and Hongyang JINGcoll.ge of mat.rial sci.nce and eng.neering, Tianjin University, Tianjin 300072, China coll. of mat. sci. and eng. Tianjin Univ. Tianjin 300072 China

A new welding electrode, low transformat.on temperature electrode (LTTE), was introduced in this paper. It was described in design principle, mechanics, chemical compositions of their deposited metal and manufacturing methods. It was proved that the best transformat.on starting temperature from austenite to martensite of the deposited metal of LTTE was at about 191℃ and it was obtained by adding alloying elements such as Cr, Ni, Mn and Mo. The microstructure of the weld metal of the LTTE was low carbon martensite and residual austenite. The compressive residual stress was induced around the weld of the LTTE and the -145 MPa in compression could be obtained in middle of weld metal. The fatigue tests showed that the fatigue streng.h of the longitudinal welded joints welded with the LTTE at 2×106 cycles was improved by 59% compared with that of the same type of welded joints welded with conventional E5015 and the fatigue life was increased by 47 times at 162 MPa. It is a very valuable method to improve the fatigue performance of welded joints.

关键词： Low transformat.on temperature electrode Compressive residual stress Fatigue streng.h Welded joints

Laser Surface Hardening of 9CrSi Steel

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Journal of mat.rials sci.nce & Technology 2002年第1期18卷 17-20页

作者： Nunghee RYU and Sunggoon KANGDivision of mat.rials sci.nce and eng.neering, coll.ge of eng.neering, Hanyang University, Korea [ Manuscript received August 7, 2001, in revised form September 20, 2001] Div. of mat. sci. and eng. Coll. of Eng. Hanyang Univ. Hanyang South Korea

The effects of laser hardening parameters such as beam power, beam diameter and scanning rate on microstructure and hardness of 9CrSi steel were investigated. The microstructure of the surface layer of 9CrSi steel was changed from pearlite to martensite, retained austenite and carbide by laser hardening. The depth of the hardened layer increased with increasing laser energy density and the surface hardeness increased by 3-5 times as high as the untreated steel. The laser hardened surface had good wear resistance due to martensite and carbide in the surface layer. The wear mode at low speed was abrasive, while the wear mode at high speed was adhesive.

关键词： Laser hardening Martensite Hardeness Phase trasformat.on

Production,Properties and Microstructures of Mg-RE-Zn-Zr(RE=MM,Nd) Alloy

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Journal of mat.rials sci.nce & Technology 2002年第4期18卷 378-380页

作者： Kun YU, Wenxian LI and Songrui LIcoll.ge of mat.rials sci.nce and eng.neering, Central South University, Changsha 410083, China coll. of mat. sci. and eng. Central South Univ. Changsha 410083 China

The Mg-MM and Mg-Nd master alloys were prepared through the ingot metallurgy method under the protection of a special flux. The thermodynamic behaviors of different rare earth elements in the molten Mg alloys were investigated. Two experimental alloys, Mg-3.0 wt pct MM-0.7 wt pct Zn-0.7 wt pct Zr and Mg-2.8 wt pct Nd-0.7 wt pct Zn-0.7 wt pct Zr, were prepared. The hardness and tensile properties of experimental alloys were measured and the microstructures were observed. The results showed that the rare earth elements could react greatly with the Mg chloride in the flux. The Mg-Nd-Zn-Zr alloy displayed a good aging hardening effect. The dispersed metastable phase ? (Mg3Nd) is an important streng.hening phase to improve the tensile properties of this alloy. So the Mg-Nd-Zn-Zr alloy has better tensile properties and elongation than those of the Mg-MM-Zn-Zr alloy, and the ductile fracture character could be observed. The microvoid coalescence is the dominant fracture mechanism in this alloy.

关键词： Mg-RE-Zn-Zr alloy Rare earth Microstructures and properties

In-situ A1/24Si Functional Graded mat.rials Prepared by Electromagnetic Separation

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Journal of mat.rials sci.nce & Technology 2002年第5期18卷 385-386页

作者： KeLI JunWANG DaSHU BaodeSUN YaoheZHOU coll. of mat. sci. and eng. Shanghai Jiaotong Univ. Shanghai 200030 China

Cylinder-like in-situ AI/24Si FGMs were produced by using electromagnetic separating process. Si primary phase reinforced layer with volume fraction as high as 16 pct was formed at the outer region of the cylinder-like samples where the local hardness and wear resistance were enhanced remarkably. Moreover, both of streng.h and ductility in the inner region provided insurance of reliable streng.h for this as-cast gradient mat.rial. It indicated that general mechanical properties such as good wear resistance at the outer region and good ductility in the central part could be obtained with the optimized redistribution of the Si primary particles under the electromagnetic force.

关键词： FGMs In-situ Electromagnetic separation