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Martensite Aging Effect and Thermal Cyclic Characteristics in Ti-Pd and Ti-Pd-Ni High Temperature Shape Memory Alloys

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Journal of mat.rials sci.nce & Technology 2001年第3期17卷 359-362页

作者： Wei Cai School of mat.rials sci.nce and eng.neering, Harbin Institute of Technology, Harbin 15000k, China Kazuhiro Otsuka Institute of mat.rials sci.nce, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan E-mail: weicai@*** Sch. of mat. sci. and eng. Harbin Inst. of Technol. Harbin 150001 China

The effect of thermal cycling and aging in martensitic state in Ti-Pd-Ni alloys were investigated by DSC and TEM observations. It is shown that the thermal cycling causes the decreases in M, and Af temperatures in Ti50Pd50-xNix (x=10, 20, 30) alloys, but no obvious thermal cycling effect was observed in Ti50Pd50Pd40Ni10 alloys and the aging effect shows a curious feature, i.e., the Af temperature does not saturate even after relatively long time aging, which is considered to be due to the occurrence of recovery recrystallization during aging.

关键词： Ti Martensite Aging Effect and Thermal Cyclic Characteristics in Ti-Pd and Ti-Pd-Ni High Temperature Shape Memory Alloys Pd Ni

AC Complex Impedance Analysis of Doped Strontium Titanate Multifunctional Ceramics

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Journal of mat.rials sci.nce & Technology 2002年第5期18卷 479-480页

作者： QingXU WenCHEN DuanpingHUANG RunzhangYUAN Sch. of mat. sci. and eng. Wuhan Univ. of Technol. Wuhan 430070 China

Doped SrTiO3 capacitor-varistor multifunctional ceramics were fabricated by a single sintering process. AC complex impedance analysis was performed to investigate electrical features of grains and grain boundaries for both as-reduced ceramic and reoxidized ceramics. The results showed that the as-reduced ceramic exhibited inductive response at high frequencies above 2 MHz, which is attributed to the contribution of electron behavior in semiconducting grains. The high frequency inductive response disappeared in impedance plots of reoxidized ceramics.

关键词： Strontium titanate Impedance Grain Capacitor

Measurement and Analyses of Molten Ni-CO-Al Alloy Density

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Journal of mat.rials sci.nce & Technology 2003年第5期19卷 388-390页

作者： Feng.XIAO and Liang FANGDepartment of mat.rials sci.nce and eng.neering, Chongqing Institute of Technology, Chongqing 400050, China Dept. of mat. sci. and eng. Chongqing Inst. of Technol. Chongqing 400050 China

The density of molten Ni-Co-AI alloy was measured using a modified pycnometric method. It has been found that the density of the molten Ni-Co-AI alloy decreases with increasing temperature, Co concentration and the ratio of Co concentration to Ni concentration in the alloy. The coefficient of volume expansion of the molten Ni-Co-AI alloy decreases with increasing Co concentration and the ratio of Co concentration to Ni concentration. The temperature coefficient of density increases with increasing the Co concentration or the ratio of Co concentration to Ni concentration in the alloy. The density of the molten Ni-Co-AI alloy as functions of both temperature and Co concentration was expressed.

关键词： Density Modified pycnometric method Ni-Co-Al alloy

Study on the Thermal Expansion and Thermal Cycling of AlNp/Al Composites

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Journal of mat.rials sci.nce & Technology 2002年第1期18卷 62-65页

作者： Qiang ZHANG, Gaohui WU, Dongli SUN and Bofeng.LUANSchool of mat.rials sci.nce and eng.neering, Harbin Institute of Technology, Harbin 150001, China [ Manuscript received January 8, 2001, in revised form April 13, 2001] Sch. of mat. sci. and eng. Harbin Inst. of Technol. Harbin 150001 China

The AIN particle reinforced aluminum mat.ix composites with 50% volume fraction were fabricated by squeeze-casting technology. The thermal expansion behavior and its response to thermal cycling were studied between 20℃ and 400℃. Compared with four theoretical models, the measured CTEs of the composite lie within the elastic bounds derived by Schapery’s analysis. Schapery’s model and Kerner’s model agree well with the CTEs of the composites at lower temperature and elevated temperature, respectively. Strain hysteresis was observed between heating and cooling curves during cycling. This was attributed primarily to the anelastic behavior of the mat.ix induced by mat.ix residual stresses.

关键词： AIN Aluminum mat.ix composite Thermal expansion Thermal cycling

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

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Journal of mat.rials sci.nce & 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 School 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

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 estimat.d 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

Effect of Preparation Atmosphere on the Structure and Properties of Vanadium Pentoxide Xerogel Films

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Journal of mat.rials sci.nce & Technology 2004年第3期20卷 365-367页

作者： Wen CHEN Manzhu KB Qing XU Quanyao ZHU Liqiang MAI Li LI School of mat.rials sci.nce and eng.neering, Wuhan University of Technology,Wuhan 430070, China Sch. of mat. sci. and eng. Wuhan Univ. of Technol. Wuhan 430070 China

In this article, the vanadium pentoxide sols are synthesized by two different routes (melted and quenched in oxygenatmosphere or in air). The structure and properties of the vanadium pentoxide xerogel films are characterized byXRD, ESR, cyclic voltammograms curves and UV-visible transmittance analysis. The results show that the sampleprepared in oxygen has poorer crystallization. lower content of V^(4+) ions and higher Li^+ insertion capacity comparedwith that prepared in air.

关键词： Preparation atmosphere V_2O_5 Structure Properties

High Temperature Deformat.on of Al_2O_3/Cu Composites

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Journal of mat.rials sci.nce & Technology 2001年第3期17卷 325-328页

作者： Jianjun WU. Yun ZHANG, Yanfei JIANG and Meiyun XUE Department of mat.rial sci.nce and eng.neering, Hebei University of Technology, Tianjin 300130, China Tingquan LEI School of mat.rials sci.nce and eng.neering, Harbin Institute of Technology, Uarbin 15000 Dept. of mat. sci. and eng. Hebei Univ. of Technol. Tianjin 300130 China

This work concerns with the high temperature deformat.on of internally oxidized Al2O3/Cu composites. The investigation revealed that dispersive alumina can obstruct dislocation sliding and define the subgrain size thereby improve significantly the streng.h of the mat.rials at high temperature. The sliding of dislocations is a main deformat.on mechanism in the given temperature range. The sliding of grain boundary and diffusive creep play important roles at high temperature and low strain rate. The dispersoids can raise the recrystallization temperature to higher than 1223 K. Dynamic recovery is a main softening way under the experimental conditions. Higher deformat.on rate and lower deformat.on temperature imply a higher flow stress.

关键词： High Temperature Deformat.on of Al2O3/Cu Composites Cu Al

Effect of Rare Earth on Thermal Shock Resistance of Steel 9Cr2Mo

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Journal of Rare Earths 2001年第2期19卷 153-156页

作者：李慧郭铁波 col.. of mat. sci. and Chem. eng. Yanshan Univ. Qinhuangdao 066004 China

The effect of rare earth elements on thermal shock resistance of col. roller steel 9Cr2Mo was investigated by means of X-ray diffractometry and optical microscopy. Experimental results show that the process of carbide precipitation of heat effect zone is restrained by adding RE elements in steel 9Cr2Mo. Therefore, thermal shock resistance of this steel can be improved.

关键词： rare earths steel 9Cr2Mo thermal shock resistance

Synthesis and Enhanced Superplasticity of the Zirconia-dispersed Alumina Nanocomposite

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Journal of mat.rials sci.nce & Technology 2005年第1期21卷 79-82页

作者： Guoqing CHEN, Kaifeng.ZHANG, Wenbo HAN and Junting LUOSchool of mat.rials sci.nce 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 mat.rial is a typical intra/inter granular nanocomposite with uniform distribution of the zirconia grains in the alumina mat.ix. 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