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Microstructure and Performance of 2Y-PSZ/TRIP Steel Composites

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Journal of mat.rials sci.nce & Technology 2003年第2期19卷 137-140页

作者： Yingkui GUO, Yu ZHOU, Dongbo LI, Xiaoming DUAN and Tingquan LEISchool of mat.rials sci.nce and eng.neering, Harbin Institute of Technology, Harbin 150001, China Sch. of mat. sci. and eng. Harbin Inst. of Technol. Harbin 150001 China

2Y-PSZ/TRIP steel composites have been sintered by hot-pressing method. Their microstructure and mechanical properties were investigated by means of SEM, TEM, XRD and static tension, split Hopkinson pressure bar method. The results showed that the streng.h and elastic modulus of 2Y-PSZ/TRIP steel composites at room temperature decreased with the increase of 2Y-PSZ content. The main reason was that the combining streng.h was quite weak between the grains of ZrO2. Distortion induced martensite transformat.on and plasticity during the dynamic loading increased the streng.h and distortion capability of the composites. The transformat.on was carried out mainly through twins format.on. The shape of martensite induced by distortion was lamellate with substructures of twins. The habit plane was near {259}T with no mid-ridge and no explosion phenomena. The interface was straight between the austenite and martensite induced by distortion. The increase of 2Y-PSZ content, on the one hand, made the composite dynamic flow stress improved. Thereby, the fracture streng.h was improved. On the other hand, it depressed both the distortion capability and the martensite transformat.on induced by distortion. This resulted in the decrease of dynamic fracture streng.h.

关键词： 2Y-PSZ/TRIP steel composites Distortion induced martensite transformat.on Transformat.on plasticity Dynamic fracture streng.h

ANISOTROPY OF (1×1)-SURFACE FREE ENERGIES OF CRYSTALS

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Acta Metallurgica Sinica(eng.ish Letters) 2001年第6期14卷 485-492页

作者： Z.M. Yu (Department of mat.rials sci.nce and eng.neering, Central South University, Changsha 410083, China) A. Flodstrom (Royal Institute of Technology, KTH, Office of the President, Valhallavdgen 79, S-100 44 Stockholm, Sweden) Dept. of mat. sci. and eng. Central South Univ. Changsha 410083 China

The surface free energy (SFE) of (1× 1)-surfaces of crystals, without reconstructionand adsorption, is calculated using a bond-broken mode. In the mode, the potentialenergy of the crystals is treated as a sum of the energies of the bonds connectingpair-wise atoms (u-bonds). The SFE is calculated based on the bond energy and thearea density of dangling bonds which depends on the structure of the surface. Theresults provide a general expression for the SFE in terms of the bond energy (E)and the bond leng.h (do) of the crystal and Miller indices hkl. The anisotropy ofthe SFE is therefore completely determined with the expression. As the examples,considering the nearest-neighboring bonding, the SFEs of sc, fcc, bcc and cth (cubictetrahedral) crystals are discussed, respectively. Wulff plots of bcc and fcc crystalsare then obtained. The equilibrium forms (EFs) of these crystals ave consequentlygot from their Wulff plots, respectively. It is found that the EFs of bcc and fcc arerespectively the rhombic dodecahedron and the truncated-octahedron that are their firstBrillouin zones, respectively.

关键词： surface free energy crystal geometrical thermodynamics

TENSILE STReng.H AND CREEP RESISTANCE OF Mg-9Al-1Zn BASED ALLOYS WITH CALCIUM ADDITION

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Acta Metallurgica Sinica(eng.ish Letters) 2001年第5期14卷 330-334页

作者： Y.S. Sun, W.M. Zhang and X.G. Mm Department of mat.rials sci.nce and eng.neering, Southeast University, Nanjing 210096, China Dept. of mat. sci. and eng. Southeast Univ. Nanjing 210096 China

Small amount of calcium addition to the Mg-9Al-0.8Zn-0.2Mn (AZ91) alloy resulted in obvious influence on mechanical properties. The yield streng.h of the alloys increased with the increase of Ca addition and the maximum streng.h was obtained from the alloy containing 0.15% of Ca. The creep resistance at the temperatures between 150-220°C was also significantly increased with Ca addition. The creep rate (at 200°C, 50 MPa) of the alloy with 0.15% Ca addition was one order of magnitude lower than that of the base alloy (AZ91). Microstructural observations revealed that the addition of calcium refined the microstructure and enhanced the thermal stability of the β precipitates, which accounted for the improvement of creep resistance at high temperatures.

关键词： Additives Aluminum alloys Calcium Creep Tensile streng.h

Comparison of the Molecular Interaction Volume Model with the Wagner Formulae in the Zn-Pb-In and Zn-Sn-Cd-Pb Dilute Solutions

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Journal of mat.rials sci.nce & Technology 2004年第3期20卷 279-284页

作者： Dongping TAO Zhuo CHEN Dunfang LI Yifeng.GAO Qianghua SHEN School of mat.rials and Metallurgical eng.neering, Kunming University of sci.nce and Technology, Kunming 650093, China Sch. of mat. and Metall. eng. Kunming Univ. of Sci. and Technol. Kunming 650093 China

The coordination numbers in the molecular interaction volume model (MIVM) can be calculated from the commonphysical quantities of pure liquid metals. A notable feature of the model lie in its capability to predict the ther-modynamic properties of solutes in the Zn-Pb-In and Zn-Sn-Cd-Pb dilute solutions using only the binary infinitedilute activity coefficients, and the predicted values are in good agreement with the experimental data of the dilutesolutions.

关键词： Activity Prediction Dilute metal solution Molecular interaction volume model

UV Spectral Analysis of the Chemical Modification and Photolysis of Acetylacetone Modified Alumina Aqueous Solution

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Journal of mat.rials sci.nce & Technology 2004年第5期20卷 639-640页

作者： Cheng.in JING, Xiujian ZHAO, Haizheng.TAO, Xina WANG and Aiyun LIUKey Laboratory of Silicate mat.rials sci.nce and eng.neering, Ministry of Education, Wuhan University of Technology, Wuhan 430070, China Lab. of Silicate mat. sci. and eng. Wuhan Univ. of Technol. Wuhan 430070 China

Acetylacetone was firstly introduced into the aqueous media with the presence of aluminum sec-butoxide and pep-tizator. It was confirmed that the UV (ultraviolet) absorption band of acetylacetone underwent 14 nm of red-shift due to the format.on of the six-membered ring of the complex between alumina and acetylacetone in the aqueous solution. It was also found that the chemical modification can be dissociated by the UV irradiation with a waveleng.h shorter than 286 nm as a result of the excitation of π-π* transition in the complex.

关键词： Chemical modification Aluminum sec-butoxide Acetylacetone Photolysis

IMPROVEMENT OF CARBIDE MORPHOLOGY ANDMECHANICAL PROPERTIES OF Cr12MoV STEELS

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Acta Metallurgica Sinica(eng.ish Letters) 2000年第5期13卷 1053-1058页

作者： Cui, X.H. Jiang, Q.C. Wang, S.Q. He, Z.M. Sch. of mat. sci. and eng. Jilin Univ. of Technol. Changchun 130025 China

Compared with conventional cast Cr12MoV steel and forged Cr12MoV steels, carbide morphology and properties of modified cast Cr12MoV steels were investigated by performing hardness test, impact test, fracture toughness test, fatigue crack propagation test, metallographic examination and quantitatively metallographic analysis. The results indicate that the carbide morphology in modified cast steel is characterized by uniformly-distributed granular carbide, which is different from that of conventional cast steel, but similar to that of forged steel. the impact toughness of modified cast steel is distinctly increased to 12.75 J/cm2 from 6.8 J/cm2 in the conventional cast steel with networked carbide, because of carbide granulation. Furthermore, The fracture toughness and fatigue-crack-propagation threshold of modified cast steel are not only higher than that of the conventional cast steel, but also higher than that of the forged steels.

关键词： Alloys Carbides Mechanical properties Morphology

Thermoelectric properties of porous (Bi_(0.15)Sb_(0.85))_2Te_3 thermoelectric mat.rials

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Journal of University of sci.nce and Technology Beijing 2003年第5期10卷 39-43页

作者： Guiying Xu, Tingjie Chen, Jianqiang Liu, and Zhangjian ZhouLaboratory of Special Ceramics and Powder Metallurgy, mat.rials sci.nce and eng.neering School, University of sci.nce and Technology Beijing, Beijing 100083, China Lab. of Special Ceramics Mat. Sci. and Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

In order to obtain thermoelectric mat.rials with high figure of merit, theconcept of Hollow (Vacuum) Quantum Structure or Effect and related thermoelectric mat.rials designwere proposed. To demonstrate the theory, the mat.rials of (Bi_(0.15)Sb_(0.85))_2Te_3 with porousstructure have been fabricated. Their thermoelectric properties and the microstructure wereinvestigated and compared with their density structure. It was found that the porous structure couldimprove their properties greatly.

关键词： thermoelectric mat.rials Bi_xSb_(1-x) Bi_2Te_3 hollow quantum effect

CHEMICAL PRETREATMENTS OF THE SURFACE OF WC-15wt%Co WITH DIAMOND COATINGS

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Acta Metallurgica Sinica(eng.ish Letters) 2001年第2期14卷 143-147页

作者： S. Liu, Z.M. Yu, D.Q. Yi and Y.X. Li (Department of mat.rials sci.nce & eng.neering, Central South University, Changsha 410083, China) (Hunan Yin Zhou Nonferrous Metals Hi-Tech. Ltd. Company, Changsha 410083, China) Dept. of mat. sci. and eng. Central South Univ. Changsha 410083 China

Diamond films were deposited on the cemented carbide WC-15%Co substrates by a hot-filament chemical vapor deposition (HF CVD) reactor. The substrate surfaces were chemically pretreated by the following two-step etching method: first using Murakami reagent for 1-3 min, and second using an HNO3:HCl=1:1 solution for 10-40 min. It is indicated that the Co content of the substrate surfaces could be reduced from 15% to 0.81-6.04% within the etching depth of 5-10μm, the surface roughness of the substrates was increased up to Ra=1.0μm, and the substrates hardness was decreased from 89.0 HRA to 83.0 HRA after the two-step etching. It is observed that the morphologies of the diamond films on the WC-15%wt Co substrates emerge in various shapes. The indentation testing shows that the good adhesion between diamond film and the substrate after HF CVD deposition could be obtained.

关键词： Chemical vapor deposition Cobalt Diamond films Surface treatment Tungsten carbide

Laser Shock Processing of an Austenitic Stainless Steel and a Nickel-base Superalloy

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Journal of mat.rials sci.nce & Technology 2003年第5期19卷 402-404页

作者： Huaming WANG, Xijun SUN and Xiaoxuan LILaboratory of Laser mat.rials Processing and Surface eng.neering, School of mat.rials sci.nce and eng.neering, Beihang University (formerly Beijing University of Aeronautics and Astronautics), Beijing 100083, China Lab. of Laser mat. Proc. Sch. of Mat. Sci. and Eng. Beijing Univ. of Aero. and Astron. Beijing 100083 China

An austenitic stainless steel 1Cr18Ni9Ti and a solid solution-streng.hened Ni-base superalloy GH30 were shock processed using a Q-switched pulsed Nd-glass laser. Microstructure, hardness and residual stress of the laser shock processed surface were investigated as functions of laser processing parameters. Results show that high density of dislocations and fine deformat.on twins are produced in the laser shock processed surface layers in both the austenitic stainless steel and the nickel-base superalloy. Extensive strain-induced martensite was also observed in the laser shock processed zone of the austenitic steel. The hardness of the laser shock processed surface was significantly enhanced and compressive stress as high as 400 MPa was produced in the laser shock processed surface.

关键词： Laser shock processing Austenitic stainless steel Nickel-base superalloy Surface mechanical properties Residual stress