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Journal of materials Science & Technology 2004年第5期20卷 586-588页

作者： Guili LIU, Rongde LI and Zhenping ZHOUsch.ol of materials Science and eng.neering, Shenyang University of Technology, Shenyang 110023, China sch. of Mat. Sci. and eng. Shenyang Univ. of Technol. Shenyang 110023 China

A model of liquid ZA27 cast alloy is established according to molecular dynamics theory and an atomic structural model of co-existent a phase and liquid is also presented by means of computer programming. Recursion method is adopted to calculate the electronic structure of RE (rare earth) in grains and around phase boundaries respectively. The calculation shows that RE is more stable around phase boundaries than in grains, which explains the fact that the solution of RE in a phase is less, and RE mainly aggregates in front of phase boundary. The calculations of bonding order integrals also show that RE in front of phases hardly solidify onto the grain surfaces as active element so as to prevent grains growth and refine the grains. As a result, the modification mechanism of RE may be explained from the view of electronic structure.

关键词： Atomic structural model Recursion method Electronic structure Modification mechanism Rare easth

Gibbs Free Energy and Activation Energy of ZrTiAlNiCuSn Bulk Glass Forming Alloys

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Journal of materials Science & Technology 2004年第3期20卷 298-300页

作者： Jianfei SUN Jun SHEN Zhenye ZHU Gang WANG Dawei XING Yulai GAO Bide ZHOU sch.ol of materials Science and eng.neering, Harbin Institute of Technology, Harbin 150001,China sch. of Mat. Sci. and eng. Harbin Inst. of Technol. Harbin 150001 China

The Gibbs free energy differences between the supercooled liquid and the crystalline mixture for the (Zr_(52.5)Ti_5Al_(10)-Ni_(14.6)Cu_(17.9))_((100-x)/100)Sn_x (x=0, 1, 2, 3, 4 and 5) glass forming alloys are estimated by introducing the equationproposed by Thompson, Spaepen and Turnbull. It can be seen that the Gibbs free energy differences decrease firstas the increases of Sn addition smaller than 3, then followed by a decrease due to the successive addition of Snlarger than 3, indicating that the thermal stabilities of these glass forming alloys increase first and then followed by adecrease owing to the excessive addition of Sn. Furthermore, the activation energy of Zr_(52.5)Ti_5Al_(10)Ni_(14.6)Cu_(17.9) and(Zr_(52.5)Ti_5Al_(10)Ni_(14.6)Cu_(17.9))_(0.97)Sn_3 was evaluated by Kissinger equation. It is noted that the Sn addition increases theactivation energies for glass transition and crystallization, implying that the higher thermal stability can be obtainedby appropriate addition of Sn.

关键词： Bulk glass forming alloy Supercooled liquid Gibbs free energy Activation energy Kissinger equation

Influence of Bias on the Properties of Carbon Nitride Films Prepared by Vacuum Cathodic Arc Method

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Journal of materials Science & Technology 2004年第6期20卷 735-738页

作者： Zhimin ZHOU, Lifang XIA and Mingren SUNsch.ol of materials Science and eng.neering, Harbin Institute of Technology, Harbin 150001, China sch. of Mat. Sci. and eng. Harbin Inst. of Technol. Harbin 150001 China

Carbon nitride films have been synthesized in a wide range of biases from 0 to -900 V by vacuum cathodic arc method. The N content was about 12.0-22.0 at. pct. Upon increasing the biases from 0 to -100 V, the N content increased from 15.0 to 22.0 at. pct which could be attributed to the knot-on effect. While the further increasing biases led to the gradual falling of the N content to 12.0 at. pct at -900 V due to the enhancement of the sputtering effect. Below -200 V, with the increasing biases the sp2C fraction in the films decreased, as a result of vvhich the I(D)/I(G) fell in the Raman spectra and the sp peaks also showed the decreasing tendency relative to the s peaks in the VBXPS (valence band X-ray photoelectron spectroscopy). While above -200 V, the sp2C fraction increased and the films became graphitinized gradually, accompanying which the I(D)/I(G) rose from -200 V to -300 V and the Raman spectra even shovved the graphite characteristic above -300 V and the sp peaks rose again relative to the s peak. The carbon nitride films mainly consist of three types of bonding: CC, sp2CN and sp3CN bonds. In the first stage the sp3CN relative ratio rises and falls in the second stage, which corresponded well with the variation of the sp2C in the films. The subpiantation mechanism resulting from the effect of ion energy played an important role in deciding'the variation of the microstructure of the carbon nitride films.

关键词： Carbon nitride Vacuum cathodic arc Raman spectroscopy X-ray photoelectron spectroscopy

High Temperature Tensile Properties of 30 vol. pct ZrCp/W Composite

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Journal of materials Science & Technology 2003年第2期19卷 167-170页

作者： Yujin WANG, Yu ZHOU, Guiming SONG and Tingquan LEI sch.ol of materials Science and eng.neering, Harbin Institute of Technology, Harbin 150001, China sch. of Mat. Sci. and eng. Harbin Inst. of Technol. Harbin 150001 China

In order to improve the high temperature streng.h of tungsten, 30 vol. pct ZrC particles were added to the tungsten matrix to form a 30ZrCp/W composite. The tensile properties from 20C to 1880C of the composite were examined. It was shown that with increasing testing temperature, the nonlinearity of the stress strain curve of 30ZrCp/W composite becames obvious over 1200C and the Young's modulus decreases and the elongation increases. The ultimate tensile streng.h increases at first and then decreases with increasing testing temperature. The maximum streng.h of 431 MPa was obtained at 1000C. The streng.hening mechanism at high temperatures is the load transfer to ZrC particles and dislocation streng.hening of the tungsten matrix with an effect of grain boundary streng.hening.

关键词： ZrCp/W composite Tensile streng.h High temperature Streng.hening mechanism Load transfer Dislocation streng.hening

Fabrication of ZrO_2/Mo-Si/Ni Functionally Graded Material by Dip-Coating

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Journal of materials Science & Technology 2003年第1期19卷 63-65页

作者： Mingwei LI, Jingchuan ZHU, Zhongda YIN and Gang Zeng.0}ol of materials Science and eng.neering, Harbin Institute of Technology, Harbin 150001, China sch. of Mat. Sci. and eng. Harbin Inst. of Technol. Harbin 150001 China

A slurry dip-coating technique was developed for fabrication of Zr02/Mo-Si/Ni functionally graded material (FGM)on the stainless steel substrate. The rheological behavior of ZrO2-Ni-ethanol slurry was characterized by viscositytest. The amount of polyvinyl butyral (PVB) additives, which served as the dispersant and binder in ZrO2-Ni-ethanolslurry, was optimized. The results showed that the characters of mixed slurries with added 9 vol. pct (relativelyto total powders) MoSi2 powders prepared by mechanical alloying changed little. The stainless steel substrate wascoated several times by dipping in the slurries, and followed by drying in air every dipping. After debinding in Arin graphite die, the coated FGM plate was finally hot pressed at 1300℃ for 1 h under the pressure of 5 MPa in Arin the same die. Microstructural observations of the sintered FGM specimens revealed that the graded layers wereformed on the stainless steel substrate, in which no cracks were observed.

关键词： Slurry dip-coating technique Functionally graded material (FGM) Polyvinyl butyral (PVB)

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

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Journal of materials Science & Technology 2003年第2期19卷 137-140页

作者： Yingkui GUO, Yu ZHOU, Dongbo LI, Xiaoming DUAN and Tingquan LEIsch.ol of materials Science 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 transformation and plasticity during the dynamic loading increased the streng.h and distortion capability of the composites. The transformation was carried out mainly through twins formation. 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 transformation induced by distortion. This resulted in the decrease of dynamic fracture streng.h.

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

Coarsening Manner and Microstructure Evolution of Al-In Hypermonotectic Alloy during Rapidly Cooling Process

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Journal of materials Science & Technology 2002年第3期18卷 241-244页

作者： Yuan LIU, Jingjie GUO, Jun JIA, Yanqing SU, Hongsheng.DING, Jiuzhou ZHAO and Xiang XUEsch.ol of materials Science and eng.neering, Harbin Institute of Technology, Harbin 150001, China [ Manuscript received April 13, 2001, in revised form June 2,5, 2001] sch. of Mat. Sci. and eng. Harbin Inst. of Technol. Harbin 150001 China

A numerical model reflecting the real physical processes well has been developed to predict the coarsening manner of the second phase droplets and the microstructural evolution under the common action of nucleation, diffusional growth, colliding coagulation during rapid cooling Al-ln hypermonotectic alloys. The model reflects the real physical processes well and is also applicable to other immiscible alloys.

关键词： Al-In immiscible alloy Coarsening Microstructure

Synthesis and Enhanced Superplasticity of the Zirconia-dispersed Alumina Nanocomposite

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Journal of materials Science & Technology 2005年第1期21卷 79-82页

作者： Guoqing CHEN, Kaifeng.ZHANG, Wenbo HAN and Junting LUOsch.ol of materials Science and eng.neering, Harbin Institute of Technology, Harbin 150001, ChinaProf., Ph.D., sch. of Mat. Sci. and eng. Harbin Inst. of Technol. Harbin 150001 China

A series of alumina-zirconia composites with various grain sizes were prepared from the nano-sized powders with different agglomerations. Microstructural analysis of the sintered compacts indicates that the as-sintered material is a typical intra/inter granular nanocomposite with uniform distribution of the zirconia grains in the alumina matrix. Superplastic deep drawing test under different conditions demonstrates that dense Al2O3/ZrO2 samples with average grain size of 230 nm can be elongated to a dome height of at least 12 mm at the punch rate of 0.6 mm·min-1 at 1400℃. Further drawing tests show that for the composites with larger grain size, such elongation cannot be achieved at such a strain rate.

关键词： Nanocomposite Synthesis Microstructure Superplasticity

Three-Dimensional Rigid-Plastic FEM Simulation of Bulk Forming Processes with New Contact and Remeshing Techniques

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Journal of materials Science & Technology 2001年第3期17卷 329-332页

作者： Debin Shan and Youngsuk Kim sch.ol of Mechanical eng.neering, Kyungpook National University, Taegu 702-70 1, South Korea Hyunsoo Kim Graduate sch.ol of Mechanical eng.neering, Kyungpook National University, Taegu 702-701, South Korea E-mail: shandb@public sch. of Mech. eng. Kyungpook Natl. Univ. Taegu 702-701 South Korea

Some techniques such as die surface description, contact judgement algorithm and remeshing are proposed to improve the robustness of the numerical solution. Based on these techniques, a three-dimensional rigid-plastic FEM code has been developed. Isothermal forging process of a cylindrical housing has been simulated. The simulation results show that the given techniques and the FEM code are reasonable and feasible for three-dimensional bulk forming processes.

关键词： Three-Dimensional Rigid-Plastic FEM Simulation of Bulk Forming Processes with New Contact and Remeshing Techniques FEM Simulation

Characteristics and Microstructure of a Hypereutectic Al-Si Alloy Powder by Ultrasonic Gas Atomization Process

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Journal of materials Science & Technology 2001年第1期17卷 79-80页

作者： Jun SHEN Zhuangde XIE Bide ZHOU and Qingchun LI sch.ol of materials Science and eng.neering, Harbin institute of Technology, Harbin 150O01. China Zhijun SU and Hongsheng.LE Shanghai HitaChi Electrical Appliance Co. Ltd, Shanghai 201206, China sch. of Mater. Sci. and eng. Harbin Inst. of Technol. Harbin 150001 China

A hypereutectic Al-Si alloy powder was prepared by ultrasonic gas atomization process. The morphologies, microstructure and phase constituent of the alloy powder were studied. The results showed that powder of the alloy was very fine and its microstructure was mainly consisted of Si crystals plus intermetallic compound A19FeSi3, which *** fine and uniformly distributed.

关键词： FeSi Characteristics and Microstructure of a Hypereutectic Al-Si Alloy Powder by Ultrasonic Gas Atomization Process Al