Volume 33,Issue 6,2004 Table of Contents
2004, 33(6):561-565.
Abstract:
The research and development of heat resistant Mg alloys were reviewed and alloying these alloys was mentioned as the basic method improving the properties as well as Cu, Ca, Sc and Sr, rare-earth elements. Alloying, extrusion and semi-solid process were highlighted to introduce the sliping of prismatic plane (1010) and pyramidal plane (1011) which can benefit the mechanical properties. Superplastic process was the effective method to fabricate the heat resistant Mg alloys parts.
The research and development of heat resistant Mg alloys were reviewed and alloying these alloys was mentioned as the basic method improving the properties as well as Cu, Ca, Sc and Sr, rare-earth elements. Alloying, extrusion and semi-solid process were highlighted to introduce the sliping of prismatic plane (1010) and pyramidal plane (1011) which can benefit the mechanical properties. Superplastic process was the effective method to fabricate the heat resistant Mg alloys parts.
2004, 33(6):566-570.
Abstract:
Because the technique of explosive consolidation of powders can produce high temperature and high pressure in very short time, it is promising in the exploiture of new materials especially in the consolidation of powders. However, the research of its mechanism is inadequate now. The research of the state equation of powders as well as the macroscopical and microcosmic mechanism of explosive consolidation of powders is discussed in this paper. Finally some suggestions for future development trend are put forward.
Because the technique of explosive consolidation of powders can produce high temperature and high pressure in very short time, it is promising in the exploiture of new materials especially in the consolidation of powders. However, the research of its mechanism is inadequate now. The research of the state equation of powders as well as the macroscopical and microcosmic mechanism of explosive consolidation of powders is discussed in this paper. Finally some suggestions for future development trend are put forward.
2004, 33(6):571-575.
Abstract:
The methanol crossover across the proton exchange membrane in direct methanol fuel cells (DMFC) is one of the main problems in commercialization of DMFC, which has attracted a significant attention in DMFC researches. In this article, recent investigations of methanol crossover in DMFC were summarized from the viewpoints of the methanol transfer through Nafion membrane and the effect of the methanol crossover on the DMFC performance. The present research status in decreasing or overcoming the methanol crossover in DMFC was briefly reviewed in terms of the development of new types of solid electrolyte membranes with lower methanol permeability and new types of cathode catalysts. Some problems in researches of methanol crossover were pointed out by comparing different types of solid electrolyte membranes and cathode catalysts and their effect on methanol crossover. Future research directions in methanol crossover were suggested.
The methanol crossover across the proton exchange membrane in direct methanol fuel cells (DMFC) is one of the main problems in commercialization of DMFC, which has attracted a significant attention in DMFC researches. In this article, recent investigations of methanol crossover in DMFC were summarized from the viewpoints of the methanol transfer through Nafion membrane and the effect of the methanol crossover on the DMFC performance. The present research status in decreasing or overcoming the methanol crossover in DMFC was briefly reviewed in terms of the development of new types of solid electrolyte membranes with lower methanol permeability and new types of cathode catalysts. Some problems in researches of methanol crossover were pointed out by comparing different types of solid electrolyte membranes and cathode catalysts and their effect on methanol crossover. Future research directions in methanol crossover were suggested.
2004, 33(6):576-579.
Abstract:
Thermodynamic requirements of internal oxidation of Cu-Al alloy were systematically analyzed, and the area chart of internal oxidation thermodynamics was drawn at the same time. Results indicate that the preferential oxidation area is quite large in the area chart, which is determined by the maximum and minimum partial pressure of oxygen, where =(max)O2lgP(17 611/T)+12.91, =(min)O2lgP (55 830/T)(4/3)lg[%Al]+19.95. But the practical internal oxidation area is a small part of the preferential oxidation area below the maximum partial pressure of oxygen. The volume concentration product spKand concentration of residual aluminum are such extreme minimum values that the internal oxidation can be proceeded completely. Temperature and partial pressure of oxygen should be adjusted synchronously during the control of internal oxidation. The optimum technology of internal oxidation is the adoption of high temperature of about 1 223 K, and high partial pressure of oxygen that should approach to or even be equal to the upper limit of oxygen partial pressure. Cold snap in hydrogen should be used to prevent the oxidation of copper during cooling.
Thermodynamic requirements of internal oxidation of Cu-Al alloy were systematically analyzed, and the area chart of internal oxidation thermodynamics was drawn at the same time. Results indicate that the preferential oxidation area is quite large in the area chart, which is determined by the maximum and minimum partial pressure of oxygen, where =(max)O2lgP(17 611/T)+12.91, =(min)O2lgP (55 830/T)(4/3)lg[%Al]+19.95. But the practical internal oxidation area is a small part of the preferential oxidation area below the maximum partial pressure of oxygen. The volume concentration product spKand concentration of residual aluminum are such extreme minimum values that the internal oxidation can be proceeded completely. Temperature and partial pressure of oxygen should be adjusted synchronously during the control of internal oxidation. The optimum technology of internal oxidation is the adoption of high temperature of about 1 223 K, and high partial pressure of oxygen that should approach to or even be equal to the upper limit of oxygen partial pressure. Cold snap in hydrogen should be used to prevent the oxidation of copper during cooling.
2004, 33(6):580-584.
Abstract:
aluminum alloy with different states (T6 and solution treatment) were forged at different strain rates (10-2s-1 and 102s-1) and strains. OM (optical microscope) and TEM (transmission electronic microscope) were used to observe the microstructure of 7075 aluminum alloy after hot deformation. Experiment results indicate that dynamic recrystallization for 7075 aluminum alloy is apt to occur under the higher strain rate and recrystallization mechanism is discontinuous dynamic recrystallization, dynamic recovery takes place at the lower strain rate. The second-phase particles play a very important role in the process of refinement of the grains.
aluminum alloy with different states (T6 and solution treatment) were forged at different strain rates (10-2s-1 and 102s-1) and strains. OM (optical microscope) and TEM (transmission electronic microscope) were used to observe the microstructure of 7075 aluminum alloy after hot deformation. Experiment results indicate that dynamic recrystallization for 7075 aluminum alloy is apt to occur under the higher strain rate and recrystallization mechanism is discontinuous dynamic recrystallization, dynamic recovery takes place at the lower strain rate. The second-phase particles play a very important role in the process of refinement of the grains.
6 Comparison of Axisymmetric and 3-D Thermal Elastic-Plastic Analytical Models for Beryllium Welding
2004, 33(6):585-588.
Abstract:
Both axisymmetric and 3-D models are used to simulate the temperature and stress fields of laser beam welding process of beryllium ring. It is shown that the computed results of two models are identical. The temperature and stress fields can be obtained in the quasi-balance state using the axisymmetric model and in the whole process using the 3-D model. The residual stresses at the start and the end welding are about 20 percent larger than that in the quasi-balance state.
Both axisymmetric and 3-D models are used to simulate the temperature and stress fields of laser beam welding process of beryllium ring. It is shown that the computed results of two models are identical. The temperature and stress fields can be obtained in the quasi-balance state using the axisymmetric model and in the whole process using the 3-D model. The residual stresses at the start and the end welding are about 20 percent larger than that in the quasi-balance state.
2004, 33(6):589-593.
Abstract:
使用MEVVA源对纯锆表面注入1×1016 ions/cm2至5×1017 ions/cm2剂量的钼离子,研究离子注入后其在水溶液中耐蚀性;注入时的最高温度为160℃,加速电压为40 kV。用X光电子谱(XPS)分析表面元素价态;3次极化扫描评价注入样品在0.5 mol/L硫酸水溶液中的耐蚀性,并对3次极化后的样品进行扫描电镜(SEM)观察。实验表明:随着钼离子注入剂量的增大,注入样品的耐蚀性反而下降。剂量越大,耐蚀性下降越多。注入样品的自然腐蚀电位与未注入纯锆相比发生了正移,总的趋势是随着剂量的加大,自然腐蚀电位越正。最后讨论了钼离子注入纯锆后耐蚀性下降的原因。
使用MEVVA源对纯锆表面注入1×1016 ions/cm2至5×1017 ions/cm2剂量的钼离子,研究离子注入后其在水溶液中耐蚀性;注入时的最高温度为160℃,加速电压为40 kV。用X光电子谱(XPS)分析表面元素价态;3次极化扫描评价注入样品在0.5 mol/L硫酸水溶液中的耐蚀性,并对3次极化后的样品进行扫描电镜(SEM)观察。实验表明:随着钼离子注入剂量的增大,注入样品的耐蚀性反而下降。剂量越大,耐蚀性下降越多。注入样品的自然腐蚀电位与未注入纯锆相比发生了正移,总的趋势是随着剂量的加大,自然腐蚀电位越正。最后讨论了钼离子注入纯锆后耐蚀性下降的原因。
2004, 33(6):594-597.
Abstract:
Considering terrestrial gravity and natural convection of protected gas, a calculated model of minimum temperature of spherical sample under electromagnetic levitation melting is derived. The range of minimum temperature is calculated without regard to the conditions of the heat dissipation by emission in gas. For argon, which has poor cooling ability, the heat dissipation by gas can be neglected in the temperature calulation. For helium, which has strong cooling ability, when the sample has high density, high electrical resistivity and low emissivity, the heat dissipation by gas can be neglected in the temperature calculation, too. When the sample with low density, low electrical resistivity and high emissivity, the heat dissipation by gas must be considered. When sample has high melting point, low electrical resistivity, low density, high emissivity and the gas has high cooling ability, the sample is easy to obtain undercooling under electromagnetic levitation in terrestrial gravity without additional cooling. When levitation melting sample has low melting point, high electrical resistivity, high density, low emissivity and protected gas has poor cooling ability, the sample is difficult to obtain undercoling.
Considering terrestrial gravity and natural convection of protected gas, a calculated model of minimum temperature of spherical sample under electromagnetic levitation melting is derived. The range of minimum temperature is calculated without regard to the conditions of the heat dissipation by emission in gas. For argon, which has poor cooling ability, the heat dissipation by gas can be neglected in the temperature calulation. For helium, which has strong cooling ability, when the sample has high density, high electrical resistivity and low emissivity, the heat dissipation by gas can be neglected in the temperature calculation, too. When the sample with low density, low electrical resistivity and high emissivity, the heat dissipation by gas must be considered. When sample has high melting point, low electrical resistivity, low density, high emissivity and the gas has high cooling ability, the sample is easy to obtain undercooling under electromagnetic levitation in terrestrial gravity without additional cooling. When levitation melting sample has low melting point, high electrical resistivity, high density, low emissivity and protected gas has poor cooling ability, the sample is difficult to obtain undercoling.
Fan Hongyuan
,
Fan Qinwen
,
Xiang Wenxin
,
Li Wei
,
Qiu Shaoyu
,
Ying Shihao
,
Zhang Xipeng
,
Shen Baoluo
2004, 33(6):598-601.
Abstract:
研究了铬膜和铌膜的复合对锆合金基体上制备的商流磁控溅射薄膜附着性的影响。使用扫描电镜(SEM)观察了膜层界面，用原子力显微镜(AFM)观察了膜层表而，用划痕法测定了薄膜的附着性。结果表明：膜／基界面结合良好，界面成分升降区狭窄；铬膜与铌膜组成的复合薄膜结合紧密；铬膜的组织为致密、边界孔洞少的纤维状晶粒，铬膜厚度为2μm时，晶粒仍为业微米级，但晶粒顶而已出现拱形；膜厚同为2μm时，外层1μm铌膜 内层1μm铬膜组成的复合膜的附着性分别是外层1μm铬膜 内层1μm铌膜组成的复合膜的2．35倍、2μm铬膜附着性的3倍，其原因在于膜层组织及力学性能变化、铌膜韧性好和复合顺序。因此，依靠铬膜厚度的增加米提高铬膜保护性的方法具有较大局限性，通过在一定厚度的铬膜外复合铌膜的方法则有较好的可行性。
研究了铬膜和铌膜的复合对锆合金基体上制备的商流磁控溅射薄膜附着性的影响。使用扫描电镜(SEM)观察了膜层界面，用原子力显微镜(AFM)观察了膜层表而，用划痕法测定了薄膜的附着性。结果表明：膜／基界面结合良好，界面成分升降区狭窄；铬膜与铌膜组成的复合薄膜结合紧密；铬膜的组织为致密、边界孔洞少的纤维状晶粒，铬膜厚度为2μm时，晶粒仍为业微米级，但晶粒顶而已出现拱形；膜厚同为2μm时，外层1μm铌膜 内层1μm铬膜组成的复合膜的附着性分别是外层1μm铬膜 内层1μm铌膜组成的复合膜的2．35倍、2μm铬膜附着性的3倍，其原因在于膜层组织及力学性能变化、铌膜韧性好和复合顺序。因此，依靠铬膜厚度的增加米提高铬膜保护性的方法具有较大局限性，通过在一定厚度的铬膜外复合铌膜的方法则有较好的可行性。
2004, 33(6):602-605.
Abstract:
采用溶胶-凝胶前驱体法合成了正尖晶石结构的LiMn2O4,研究了产物的结构、性能以及最佳的制备条件.结果表明,原料的配比和干胶的焙烧温度对产物的组成、结构以及颗粒形态有重要的影响.进一步的研究表明,LiMn2O4在1.0 mol·L-1HCl中酸浸120 h可得高纯度的λ-MnO2,λ-MnO2浸锂后得到Li+与LiMn2O4所形成的固溶体Li1.01Mn2O4,其锂离子脱嵌/嵌入在结构上是可逆的.固溶体Li1.01Mn2O4的形成可提高材料的锂离子筛分性能.
采用溶胶-凝胶前驱体法合成了正尖晶石结构的LiMn2O4,研究了产物的结构、性能以及最佳的制备条件.结果表明,原料的配比和干胶的焙烧温度对产物的组成、结构以及颗粒形态有重要的影响.进一步的研究表明,LiMn2O4在1.0 mol·L-1HCl中酸浸120 h可得高纯度的λ-MnO2,λ-MnO2浸锂后得到Li+与LiMn2O4所形成的固溶体Li1.01Mn2O4,其锂离子脱嵌/嵌入在结构上是可逆的.固溶体Li1.01Mn2O4的形成可提高材料的锂离子筛分性能.
2004, 33(6):606-608.
Abstract:
Three kinds of Long afterglow Sr4Al14O25: Eu2+, Dy3+ phosphor samples with various Eu2+ contents were synthesized. When the concentration of doped Eu2+ in the host was less than 0.012 mol, the emission spectra of Sr4Al14O25: Eu2+, Dy3+ has two peaks at 407 nm and 494 nm respectively, which is ascribed to two types of Eu2+ sites existing in Sr4Al14O25 matrices crystal. But the 407nm emission peak disappeared slowly with the concentration of doped Eu2+ increasing. Based on the Sr4Al14O25 crystal structure, excitation and emission spectra, the energy transfer model has been established, and a reasonable explanation was given for the experimental phenomena. In addition, the decay curves indicate that these Sr4Al14O25: Eu2+, Dy3+ phosphors have obviously a long afterglow. Especially in phosphor, the afterglow can last over 20 h in the light perception of the human eye.
Three kinds of Long afterglow Sr4Al14O25: Eu2+, Dy3+ phosphor samples with various Eu2+ contents were synthesized. When the concentration of doped Eu2+ in the host was less than 0.012 mol, the emission spectra of Sr4Al14O25: Eu2+, Dy3+ has two peaks at 407 nm and 494 nm respectively, which is ascribed to two types of Eu2+ sites existing in Sr4Al14O25 matrices crystal. But the 407nm emission peak disappeared slowly with the concentration of doped Eu2+ increasing. Based on the Sr4Al14O25 crystal structure, excitation and emission spectra, the energy transfer model has been established, and a reasonable explanation was given for the experimental phenomena. In addition, the decay curves indicate that these Sr4Al14O25: Eu2+, Dy3+ phosphors have obviously a long afterglow. Especially in phosphor, the afterglow can last over 20 h in the light perception of the human eye.
2004, 33(6):609-611.
Abstract:
研究了AlCl3-SiCl4-H2-CO2气相系统不同温度化学气相沉积Al2O3-SiO2系氧化物相组成及显微结构，分析了化学气相沉积过程机理。结果表明，CVD过程不能实现Al-Si化合物的均匀混合，不同温度沉积产物为不同变体Al2O3结合非晶SiO2或其固溶体复合氧化物，1050℃以下，随沉积温度提高，沉积物颗粒尺寸减小，1050℃可沉积出晶化较为完全的莫来石结合α—Al2O3，t—Al2O3和非晶SiO2致密涂层。
研究了AlCl3-SiCl4-H2-CO2气相系统不同温度化学气相沉积Al2O3-SiO2系氧化物相组成及显微结构，分析了化学气相沉积过程机理。结果表明，CVD过程不能实现Al-Si化合物的均匀混合，不同温度沉积产物为不同变体Al2O3结合非晶SiO2或其固溶体复合氧化物，1050℃以下，随沉积温度提高，沉积物颗粒尺寸减小，1050℃可沉积出晶化较为完全的莫来石结合α—Al2O3，t—Al2O3和非晶SiO2致密涂层。
2004, 33(6):612-614.
Abstract:
Al, Ti/Al coatings on U substrates were prepared by repeated Ar+ bombardment-magnetron sputter ion plated (MSIP). The surface morphology, cross-sectional morphology, interfaces, wear-resistance, and corrosion resistance have been investigated by Auger electron spectroscopy (AES), scanning electron microscopy(SEM), electrochemical test, and wearing test respectively. The results showed that the surface morphology of Al, Ti/Al coatings were constituted of fine grains with smooth appearance. The more wide co-existence Interface of coatings and substrates were prepared by repeated Ar+ bombardment-magnetron sputter ion plated (MSIP). The degree of protection of Uranium against corrosion and wear-resistance plated of Ti/Al coatings by repeated Ar+ bombardment-MSIP is superior to that of sole Al coatings.
Al, Ti/Al coatings on U substrates were prepared by repeated Ar+ bombardment-magnetron sputter ion plated (MSIP). The surface morphology, cross-sectional morphology, interfaces, wear-resistance, and corrosion resistance have been investigated by Auger electron spectroscopy (AES), scanning electron microscopy(SEM), electrochemical test, and wearing test respectively. The results showed that the surface morphology of Al, Ti/Al coatings were constituted of fine grains with smooth appearance. The more wide co-existence Interface of coatings and substrates were prepared by repeated Ar+ bombardment-magnetron sputter ion plated (MSIP). The degree of protection of Uranium against corrosion and wear-resistance plated of Ti/Al coatings by repeated Ar+ bombardment-MSIP is superior to that of sole Al coatings.
2004, 33(6):615-619.
Abstract:
利用表面机械处理技术在纯钛表面制备出50μm厚纳米表面层，采用金相显微镜(OM)、透射电镜(TEM)研究了处理层的微观结构。随着应变增加，晶粒逐渐细化。晶粒的细化机制为：孪晶的形成和孪晶碰撞；孪晶转变成取向不同的片状晶；片状晶转变成含有位错的胞状晶、取向不同的小角度块状晶以及取向不同的多边形亚细晶；亚细晶和片状晶转变成纳米晶。微观结构观察证实了动态再结晶促使晶粒细化。
利用表面机械处理技术在纯钛表面制备出50μm厚纳米表面层，采用金相显微镜(OM)、透射电镜(TEM)研究了处理层的微观结构。随着应变增加，晶粒逐渐细化。晶粒的细化机制为：孪晶的形成和孪晶碰撞；孪晶转变成取向不同的片状晶；片状晶转变成含有位错的胞状晶、取向不同的小角度块状晶以及取向不同的多边形亚细晶；亚细晶和片状晶转变成纳米晶。微观结构观察证实了动态再结晶促使晶粒细化。
2004, 33(6):620-623.
Abstract:
研究了TP-650颗粒增强钛基复合材料的性能与组织。结果表明复合材料的室温静拉伸强度随热处理温度的升高而增加。经炉冷处理TP-650棒材的室温拉伸强度比油冷或空冷处理的要高。TP-650的使用温度比传统高温钛合金IM1834，Ti-1100要高50℃～100℃。500℃以上，复合材料表现出良好的高温稳定性能。显微组织显示了TiC颗粒弥散分布，复合材料组织均匀，TiC和基体冶金结合，界面较小。
研究了TP-650颗粒增强钛基复合材料的性能与组织。结果表明复合材料的室温静拉伸强度随热处理温度的升高而增加。经炉冷处理TP-650棒材的室温拉伸强度比油冷或空冷处理的要高。TP-650的使用温度比传统高温钛合金IM1834，Ti-1100要高50℃～100℃。500℃以上，复合材料表现出良好的高温稳定性能。显微组织显示了TiC颗粒弥散分布，复合材料组织均匀，TiC和基体冶金结合，界面较小。
Zhang Hong
,
Feng Yong
,
Zhou Lian
,
Zhang Cuiping
,
Yu Zemin
,
Xiong Xiaomei
,
Liang Ming
,
Hao Qingbin
2004, 33(6):624-627.
Abstract:
分别采用3种方法在不同烧结温度下制备Gd211粉末。利用X射线衍射(XRD)、扫描电镜(SEM)、激光粒度分析等手段对3种制备方法进行比较研究。Gd211的成相温度约在900℃以上。随着烧结温度的升高，粉末的碳含量明显降低，但粒子尺寸逐渐增人，且由均匀的球形颗粒变成越来越来规则的大颗粒。3种制备方法相比，草酸盐共沉淀法相对复杂，但合成的材料颗粒较细且均匀，碳含呈很低，是最理想的制备Gd211的方法。
分别采用3种方法在不同烧结温度下制备Gd211粉末。利用X射线衍射(XRD)、扫描电镜(SEM)、激光粒度分析等手段对3种制备方法进行比较研究。Gd211的成相温度约在900℃以上。随着烧结温度的升高，粉末的碳含量明显降低，但粒子尺寸逐渐增人，且由均匀的球形颗粒变成越来越来规则的大颗粒。3种制备方法相比，草酸盐共沉淀法相对复杂，但合成的材料颗粒较细且均匀，碳含呈很低，是最理想的制备Gd211的方法。
2004, 33(6):628-631.
Abstract:
In this article, preparation of nano-graphite powder in steel chamber by using pure TNT ( trinitrotoluene )explosives has been introduced. X-ray Diffraction (XRD) results indicate that the black solid powder which collected from the wall and the bottom of the chamber after detonation has graphite structure and the average size of the particles of graphite is 1.86 nm~2.58 nm. Transmission electron microscopy (TEM) and micro-Raman spectroscopy confirmed that the black powder is hexagonal-graphite structure and its shape is ball or ellipsoid. Small angle X-ray Scattering (SAXRS) results revealed that the particle size of nano-graphite is 1 nm~60 nm.
In this article, preparation of nano-graphite powder in steel chamber by using pure TNT ( trinitrotoluene )explosives has been introduced. X-ray Diffraction (XRD) results indicate that the black solid powder which collected from the wall and the bottom of the chamber after detonation has graphite structure and the average size of the particles of graphite is 1.86 nm~2.58 nm. Transmission electron microscopy (TEM) and micro-Raman spectroscopy confirmed that the black powder is hexagonal-graphite structure and its shape is ball or ellipsoid. Small angle X-ray Scattering (SAXRS) results revealed that the particle size of nano-graphite is 1 nm~60 nm.
2004, 33(6):632-634.
Abstract:
Carbide and phase are two main precipitation phases in the matrix of Ti-25V-15Cr-2Al-0.2C-x(x=0, 2%Mo, 2%Nb, etc) non-burning titanium alloys. The heat treatment and thermal exposure microstructure of the alloys with different distribution state of carbide has been investigated using optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that carbide particles with smaller sizes and higher dispersity can not only refine the microstructure of the alloys, but also significantly suppress the formation of precipitates which are detrimental to the microstructural stability of the alloys. The smaller the size and the more uniform the distribution of carbide, the stronger the effect of suppressing precipitatesthus the better microstructural stability of the alloys will be obtained.
Carbide and phase are two main precipitation phases in the matrix of Ti-25V-15Cr-2Al-0.2C-x(x=0, 2%Mo, 2%Nb, etc) non-burning titanium alloys. The heat treatment and thermal exposure microstructure of the alloys with different distribution state of carbide has been investigated using optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that carbide particles with smaller sizes and higher dispersity can not only refine the microstructure of the alloys, but also significantly suppress the formation of precipitates which are detrimental to the microstructural stability of the alloys. The smaller the size and the more uniform the distribution of carbide, the stronger the effect of suppressing precipitatesthus the better microstructural stability of the alloys will be obtained.
2004, 33(6):635-640.
Abstract:
The mechanical alloying (MA) route was used to mix uniformly boron powder, FeMo powder and titanium powder. The mixed powder was vacuum hot press sintered and TiB was formed in-situ during the process. Typical microstructure of the composites has two kinds of areas under optical microscope (OM): in situ TiB reinforced Ti MMCs and the isolated unprocessed material. TEM investigation of the TiB reinforced composites show that these areas are made up of in situ TiB reinforced and Ti matrix. The size and distribution of in situ TiB are different in boundaries and inner of and Ti phases. Most of the in situ TiB needles are random distributed. The transverse section of the in situ TiB needle is hexagonal. The interface between in situ TiB and the Ti MMCs is clear, flat and sharp without any interfacial reaction. The strength and Youngs modulus of the TiB reinforced TMCs decreased with the increasing of in situ TiB volume content.
The mechanical alloying (MA) route was used to mix uniformly boron powder, FeMo powder and titanium powder. The mixed powder was vacuum hot press sintered and TiB was formed in-situ during the process. Typical microstructure of the composites has two kinds of areas under optical microscope (OM): in situ TiB reinforced Ti MMCs and the isolated unprocessed material. TEM investigation of the TiB reinforced composites show that these areas are made up of in situ TiB reinforced and Ti matrix. The size and distribution of in situ TiB are different in boundaries and inner of and Ti phases. Most of the in situ TiB needles are random distributed. The transverse section of the in situ TiB needle is hexagonal. The interface between in situ TiB and the Ti MMCs is clear, flat and sharp without any interfacial reaction. The strength and Youngs modulus of the TiB reinforced TMCs decreased with the increasing of in situ TiB volume content.
2004, 33(6):641-645.
Abstract:
When the zirconium alloy plates with the same Fe content and different Cr content were used to make the butt joints with Zr-4 alloy plates, the hydrogen content in welding samples is obviously different after corrosion and is not in proportion to the thickness of oxide films. This shows that alloying element Cr has a significant effect on hydrogen uptake performance. The hydrogen content in welding samples, in which zirconium alloy plates being used to make the butt joints with Zr-4 plates dont contain Cr, decreases sharply after corrosion. The relationship between hydrogen content and the number and size of Zr(Fe,Cr)2 second phase particles in Zr-4 with different heat-treated states indicates that the formation of Zr(Fe,Cr)2 second phase particles is the main reason that the amount of hydrogen uptake increases. Adding Nb alloying element in zirconium alloys without Cr, not only improves the corrosion resistance, but also make hydrogen uptake not to increase. The zirconium hydrides induced by tensile stress are easy to precipitate in the front of faulty fusion, and they are also easy to precipitate along the interface between molten zones and matrix. These will influence the dispersity of mechanical properties.
When the zirconium alloy plates with the same Fe content and different Cr content were used to make the butt joints with Zr-4 alloy plates, the hydrogen content in welding samples is obviously different after corrosion and is not in proportion to the thickness of oxide films. This shows that alloying element Cr has a significant effect on hydrogen uptake performance. The hydrogen content in welding samples, in which zirconium alloy plates being used to make the butt joints with Zr-4 plates dont contain Cr, decreases sharply after corrosion. The relationship between hydrogen content and the number and size of Zr(Fe,Cr)2 second phase particles in Zr-4 with different heat-treated states indicates that the formation of Zr(Fe,Cr)2 second phase particles is the main reason that the amount of hydrogen uptake increases. Adding Nb alloying element in zirconium alloys without Cr, not only improves the corrosion resistance, but also make hydrogen uptake not to increase. The zirconium hydrides induced by tensile stress are easy to precipitate in the front of faulty fusion, and they are also easy to precipitate along the interface between molten zones and matrix. These will influence the dispersity of mechanical properties.
2004, 33(6):646-650.
Abstract:
The strong magnetic phase size and its magnetic properties in FeCrCoVTiW permanent alloy were measured by M ssbauer spectrum and transmission electron microscope. The compositions of the two phases in the alloy were analyzed. The components of the 1 phase is 78Fe5Cr17Co, the components of the 2 phase is 13Fe80Cr7Co. According to the single magnetic domain theory, the computed value of coercive force of the alloy is approximately consistent with the experimental value, and the high coercive force value is resulted from the magnetic moment turn in the single magnetic domain of the alloy.
The strong magnetic phase size and its magnetic properties in FeCrCoVTiW permanent alloy were measured by M ssbauer spectrum and transmission electron microscope. The compositions of the two phases in the alloy were analyzed. The components of the 1 phase is 78Fe5Cr17Co, the components of the 2 phase is 13Fe80Cr7Co. According to the single magnetic domain theory, the computed value of coercive force of the alloy is approximately consistent with the experimental value, and the high coercive force value is resulted from the magnetic moment turn in the single magnetic domain of the alloy.
2004, 33(6):651-654.
Abstract:
In this paper, alumina ceramic coating of aluminum alloy surface was performed using micro-plasma oxidation (MPO) technology. Coating formed after short treatment time was found to consist of -Al2O3 and -Al2O3. Single -Al2O3 coatings can be gained by oxidation for 2.5 h. The growth velocity of coating thickness was 0.7 m/min during first 135 min, then that was constant. The surface density of coating was only 0.088 mg/cm2 at 15th min, then that increases gradually. The surface density increase presented a linear relationship during 15 min~60 min, and after 60 min the increase of surface density of coating is slow.
In this paper, alumina ceramic coating of aluminum alloy surface was performed using micro-plasma oxidation (MPO) technology. Coating formed after short treatment time was found to consist of -Al2O3 and -Al2O3. Single -Al2O3 coatings can be gained by oxidation for 2.5 h. The growth velocity of coating thickness was 0.7 m/min during first 135 min, then that was constant. The surface density of coating was only 0.088 mg/cm2 at 15th min, then that increases gradually. The surface density increase presented a linear relationship during 15 min~60 min, and after 60 min the increase of surface density of coating is slow.
2004, 33(6):655-658.
Abstract:
以氮化硅为基体，通过加入一定量的纳米碳粉等添加剂，成功的制备出了具有高强度和较高气孔率的氮化硅多孔陶瓷。采用阿摹米得法、一点弯曲法测试了材料的密度、气孔率及强度；用X射线衍射仪及扫描电镜对相组成及断口进行了研究。实验结果表明：加入的纳米碳粉同在Si3N4表面的SiO2或者同Si3N4颗粒本身反应，生成了极细的SiC颗粒，钉扎在β型氮化硅的晶界，可以有效的增加材料的强度。在含碳量为5％(质量分数)，1780℃下保温60min，可以制得强度大于100MPa，气孔率大于40％的氮化硅多孔陶瓷。
以氮化硅为基体，通过加入一定量的纳米碳粉等添加剂，成功的制备出了具有高强度和较高气孔率的氮化硅多孔陶瓷。采用阿摹米得法、一点弯曲法测试了材料的密度、气孔率及强度；用X射线衍射仪及扫描电镜对相组成及断口进行了研究。实验结果表明：加入的纳米碳粉同在Si3N4表面的SiO2或者同Si3N4颗粒本身反应，生成了极细的SiC颗粒，钉扎在β型氮化硅的晶界，可以有效的增加材料的强度。在含碳量为5％(质量分数)，1780℃下保温60min，可以制得强度大于100MPa，气孔率大于40％的氮化硅多孔陶瓷。
2004, 33(6):659-661.
Abstract:
The effect of melt overheating treatment on the solidification segregation of M963 cast Ni-base superalloy has been studied. The results show that the melt overheating treatment has little effect on the segregation of Al, Co and Ni; and the melt treatment at 1 923 K for 5 min caused an increase in segregation of Ti, Nb and W and a decrease in segregation of Mo and Cr obviously. It is suggested that the change of segregation is attributed to the change in the melt structure of the M963 superalloy.
The effect of melt overheating treatment on the solidification segregation of M963 cast Ni-base superalloy has been studied. The results show that the melt overheating treatment has little effect on the segregation of Al, Co and Ni; and the melt treatment at 1 923 K for 5 min caused an increase in segregation of Ti, Nb and W and a decrease in segregation of Mo and Cr obviously. It is suggested that the change of segregation is attributed to the change in the melt structure of the M963 superalloy.
2004, 33(6):662-665.
Abstract:
Polyimide (PI) materials have attracted much attention as a promising substrate in electronic packaging, on the basis of fact that PI has a low dielectric constant and the good thermal-mechanical and chemical properties. Copper offers a better electromigration-resistant performance and lower thin film resistivity as compared with other interconnects. Copper thin films were deposited on PI substrates by physical vapor deposition (PVD) method. Amorphous TiN film with thickness of 150 nm prepared by PVD was used as a diffusion barrier between Cu on PI. Effect of heat treatment up to 300 on the behavior of TiN diffusion barriers and copper film resistivity were studied. The spectra of AES depth profile indicated that TiN prevented Cu from diffusing into PI from room temperature to 300 . After treatment, the adhesion strength of copper films was measured by the peel test, the adhesion improvement by heat treatment was mainly attributed to the removal of tensile residual stress in copper films.
Polyimide (PI) materials have attracted much attention as a promising substrate in electronic packaging, on the basis of fact that PI has a low dielectric constant and the good thermal-mechanical and chemical properties. Copper offers a better electromigration-resistant performance and lower thin film resistivity as compared with other interconnects. Copper thin films were deposited on PI substrates by physical vapor deposition (PVD) method. Amorphous TiN film with thickness of 150 nm prepared by PVD was used as a diffusion barrier between Cu on PI. Effect of heat treatment up to 300 on the behavior of TiN diffusion barriers and copper film resistivity were studied. The spectra of AES depth profile indicated that TiN prevented Cu from diffusing into PI from room temperature to 300 . After treatment, the adhesion strength of copper films was measured by the peel test, the adhesion improvement by heat treatment was mainly attributed to the removal of tensile residual stress in copper films.
2004, 33(6):666-669.
Abstract:
Chromium nitride (CrN) coatings deposited by physical vapor deposition (PVD) processes have been adopted for wear protection of cutting tools and various metallic components for years. To further improve the electrochemical performances of CrN coatings, duplex CrNx coatings of various stoichimetries and gradient coating were prepared by cathodic arc evaporation. The chemical analysis was carried out by X-ray photoelectron spectroscopy (XPS). The crystallographic structure was investigated by X-ray diffraction (XRD). The composition, structure of the coatings varied as a function of nitrogen pressure. The potentiodynamic polarization was examined by Zahner IM6e electrochemical workstation, and the corrosive surface was detected by scanning electron microscopy (SEM). The results showed that the graded coating had an better electrochemical performance than duplex CrN coating. The relationship of microstructure and properties was studied, and a model of gradient CrN coating was constituted.
Chromium nitride (CrN) coatings deposited by physical vapor deposition (PVD) processes have been adopted for wear protection of cutting tools and various metallic components for years. To further improve the electrochemical performances of CrN coatings, duplex CrNx coatings of various stoichimetries and gradient coating were prepared by cathodic arc evaporation. The chemical analysis was carried out by X-ray photoelectron spectroscopy (XPS). The crystallographic structure was investigated by X-ray diffraction (XRD). The composition, structure of the coatings varied as a function of nitrogen pressure. The potentiodynamic polarization was examined by Zahner IM6e electrochemical workstation, and the corrosive surface was detected by scanning electron microscopy (SEM). The results showed that the graded coating had an better electrochemical performance than duplex CrN coating. The relationship of microstructure and properties was studied, and a model of gradient CrN coating was constituted.
2004, 33(6):670-672.
Abstract:
用氨化溅射Ga2O3薄膜的方法，成功地合成了一维GaN纳米线。用X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)和高分辨电镜(HRTEM)对样品进行了分析。生成的GaN纳米线平直光滑，其直径为20nm～90nm，长可达50μm；纳米线为高质量的单晶六方纤锌矿GaN，沿[110]方向生长。用此工艺制备GaN纳米线，避免了在制备过程中引入杂质，合成的纳米线纯度较高。
用氨化溅射Ga2O3薄膜的方法，成功地合成了一维GaN纳米线。用X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)和高分辨电镜(HRTEM)对样品进行了分析。生成的GaN纳米线平直光滑，其直径为20nm～90nm，长可达50μm；纳米线为高质量的单晶六方纤锌矿GaN，沿[110]方向生长。用此工艺制备GaN纳米线，避免了在制备过程中引入杂质，合成的纳米线纯度较高。
