Ti0.096V0.864Fe0.04合金的储氢性能研究与物相分析

研究了Ti0.096V0.864Fe0.04合金的储氢性能、热力学特性及吸放氢物相变化.研究结果表明,该合金具有较好的吸放氢压力平台特性,合金的20℃最大吸氢量达到3.75%(质量分数),氢化物生成焓变△H°为-26.6kJ·(mol H2)-1,熵变△S°为-102.5J·(K·mol H2)-1.合金颗粒度、吸放氢循环次数对合金的吸氢速度都有较大影响.该合金具有较好的抗粉化能力,经过10次吸放氢循环后合金粉的平均粒径比吸氢前仅减小约1/5.XRD及SEM分析表明,合金未吸氢前是由单一的体心立方(BCC)结构的钒基固溶体相组成;4MPa下吸氢后生成大量面心立方(FCC)结构的Ti0.096V0.864Fe0.04H2.01和少量体心四方(BCT)结构的Ti0.096 V0.864 Fe0.04H0.81两种氢化物相;50℃下对0.001MPa放氢后,合金中除Ti0.096V00864Fe0.04基BCC固溶体相外,还存在Ti0.096V0.864Fe0.04H0.81氢化物相.     

ZrTi-V-Mn-Ni系贮氢合金的相结构与电化学性能研究*

优化合金组成,设计六种锆基AB2型贮氢合金材料。XRD分析表明,当0≤x≤0.5时,Zr1-xTix(NiCoMnV)2.1贮氢合金的主相都是Laves C15,但随Ti含量的增加,Laves C14相含量增多;当用V-Fe(85.6%)合金代替Zr0.6Ti0.4(NiCoMn-VFeCr)1.7中的V时,贮氢合金中Laves C14相的含量几乎可与Laves C15相当。电化学测试表明：Zr0.9Ti0.1(NiCoMnV)2.1贮氢电极的放电容量可达340mAh/g左右,但是随着Ti含量的逐渐增加,合金电极的放电容量降低很快。以适量的（V－Fe)合金取代Zr0.6Ti0.4(NiCoMnVFeCr)1.7合金中的V和Fe,发现合金电极的第一次放电容量就能达到200mAh/g左右,并且其容量稍高于含纯V的合金电极,容量可达315mAh/g左右。     

Ti—H 合金的相变内耗

用低频(0.5—1Hz)内耗法研究了 Ti-H(0.1—1.1wt-%H)合金的相变内耗。结果表明:(1)高氢钛合金(0.8—1.1wt-%)在升、降温过程中分别于325,225℃出现内耗峰,它们与 Ti-H 合金的共析相变有关。(2)低氢钛合金(0.12wt-%)的内耗峰在共析温度以下出现。(3)中等氢含量(0.44wt-%)的钛合金降温时的内耗峰可分解为双峰,与共析沉淀和氢化物从过饱和α相中的沉淀有关。借助于差热分析实验,讨论了上述内耗峰产生的可能机制。     

Sc、Zr对Al-Mg-Mn合金再结晶行为及内耗性能的影响

为了研究微量Sc、Zr在Al-Mg-Mn合金中的作用,采用铸锭冶金方法制备了Al-6.0Mg-0.5Mn-(Sc、Zr)合金,通过光学显微镜、显微硬度、透射电镜组织观察和低频扭摆法测量内耗方法研究了微量Sc、Zr对Al-6.0Mg-0.5Mn的组织、再结晶行为及内耗性能的影响.研究表明:添加质量分数为0.21%Sc和0.15%Zr可显著细化Al-6.0Mg-0.5Mn合金铸态组织;粒状Al3Sc1-xZrx相对位错、晶界有强烈钉扎作用,抑制合金再结晶;冷变形后的Al-6.0Mg-0.5Mn-0.21Sc-0.15Zr合金的内耗表现出非线性特征,频率越低或温度越高,合金内耗Q-1越大.在频率为1Hz、应变振幅为4.6×10-5下,冷变形Al-6.0Mg-0.5Mn-0.21Sc-0.15Zr合金升温Q-1-T曲线上在326℃时产生内耗峰,该峰可由Al3Sc1-xZrx沉淀粒子与位错脱钉机制解释.微量Sc、Zr可以细化Al-Mg-Mn合金组织,抑制合金的再结晶,导致合金在升温Q-1-T曲线上产生内耗峰.     

含Ti和C的纳米复合Nd_2Fe_(14)B/α-Fe磁体研究EI北大核心

研究Ti和C添加对Nd9.4Fe79.6B11合金磁性能的影响规律。结果表明:Ti和C联合添加能够在不降低合金剩磁的情况下显著提高合金的矫顽力,最佳工艺条件下制备出的Nd9.4Fe75.6Ti4B10.5C0.5合金薄带的剩磁Br=0.91T,矫顽力Hcj=975.6kA/m,磁能积(BH)max=135.4kJ/m3。在磁体密度为6.1g/cm3时,黏结Nd9.4Fe75.6Ti4B10.5C0.5磁体剩磁Br=0.68T,内禀矫顽力Hcj=975kA/m,最大磁能积(BH)max=76 kJ/m3,性能和MQ-D磁粉制备的黏结磁体性能相当,具有低价位高性能的特点。     

含Ti和C的纳米复合Nd2Fe14B／α—Fe磁体研究

研究Ti和C添加对Nd9.4Fe79.6B11合金磁性能的影响规律。结果表明:Ti和C联合添加能够在不降低合金剩磁的情况下显著提高合金的矫顽力,最佳工艺条件下制备出的Nd9.4Fe75.6Ti4B10.5C0.5合金薄带的剩磁Br=0.91T,矫顽力Hcj=975.6kA/m,磁能积(BH)max=135.4kJ/m3。在磁体密度为6.1g/cm3时,黏结Nd9.4Fe75.6Ti4B10.5C0.5磁体剩磁Br=0.68T,内禀矫顽力Hcj=975kA/m,最大磁能积(BH)max=76 kJ/m3,性能和MQ-D磁粉制备的黏结磁体性能相当,具有低价位高性能的特点。     

淬火对V40Ti26Cr26Fe8贮氢合金的影响

淬火工艺被广泛应用于钒基固溶体贮氢合金的热处理过程中,并被认为能够有效改善合金成份均匀性,提高合金的有效放氢量.考察了淬火对V40Ti26Cr26Fe8贮氢合金放氢PCT性能的影响.合金微观结构变化的分析表明,合金在退火态时存在C14 Laves相,淬火后Laves相固溶于BCC主相中,含量下降.成分分析表明,合金BCC主相淬火后Ti含量上升.与退火处理相比,合金放氢量和平台压在淬火后均出现下降.而合金在淬火过程中产生的缺陷及应力,导致了放氢平台倾斜,滞后增大且放氢量下降.     

提高6063系铝合金强度方法的探讨

本文主要综述了不同合金元素（Mg、Si、Cu、Fe）、精炼剂、不同的细化剂（Al—Ti—B、Al-Ti—C、RE—Al—Ti—B）以及工艺参数（风冷和水冷）对Al—Mg—Si系6063铝合金组织性能的影响。     

高温退火对V30Ti33Cr27Fe10贮氢合金性能与结构的影响

研究了高温退火处理对V30Ti33Cr27Fe10贮氢合金性能与结构的影响。结果表明高温退火使放氢平台变平，平台压降低，减小了合金吸放氢后的体胀，改变了合金晶粒的形态，改善了合金基体的组织均匀性。随保温时间延长，合金晶粒长大，晶胞体积减小，吸放氢量降低，BCC主相中析出越来越多的富Ti相，富Ti相中Fe含量随保温时间延长而减少。1523K保温30min的合金具有最大的室温吸放氢量，分别为3．679，5和2．14%（质量分数）；保温3h的合金具有最好的室温吸氢动力学性能，5min内就能达到其饱和吸氢量的80％。     

Ti系合金的室温吸氢平衡压力

观测了具有α相结构的纯Ti、TiZrYAl合金，α β双相结构的TiMo、TiMoSc合金以及近β相结构的TiMoYAlFe和TiMoVYAlFe合金的吸氢PCT曲线和室温平衡压，在室温下各样品的吸氢平衡压约为10^-9～10^-16Pa；α单相合金和α β双相合金的吸氢平衡压略高于纯Ti，但其P—C等温线的斜度增大，吸氢平台长度略有缩短，近β结构合金的室温吸氢平衡压显著高于纯Ti及其它两类合金，增加Al的含量使α相TiZrYAl合金的吸氢平台长度显著缩短，但对平衡压力的影响不大。     

Internal friction of powder metallurgy (P/M) and ingot metallurgy (I/M) Al–Fe alloys at elevated temperature

Low-frequency internal friction measurements have been carried out on the powder metallurgy (P/M) and ingot metallurgy (I/M) Al–Fe alloy. Internal friction peaks can be seen at about 820–830 K and 530–620 K in the I/M alloys, but not in the P/M alloys. The former is probably due to the grain-boundary relaxation and the latter to recrystallization. Activation energies for the grain-boundary relaxation are estimated to be in two ranges: one is between 100 and 130 kJ mol–1 and the other is between 200 and 210 kJ mol–1, according to the iron content and fabrication processes. The high activation energy is given by the low iron content I/M alloys having a bamboo-like grain. It is suggested that such a difference in the activation energy is due to whether or not the solute iron diffuses into the grain boundary to lower the grain boundary energy.     

B2 Fe-Al合金中与空位有关的弛豫

利用内耗方法对空冷B2 Fe-Al合金中原子缺陷的运动特征进行了研究.在210℃(称为P1峰)和410℃(称为P2峰)附近观察到两个与样品热空位浓度密切相关的弛豫型内耗峰.研究表明,P1峰产生于应力作用下双空位(V_(Fe)V_(Al))的重新取向,而P2峰起源于反位置原子与Fe空位之间的相互作用.对于富Fe的B2 Fe-Al合金,P2峰产生于应力作用下三倍体缺陷(2V_(Fe)Fe_(Al))的重新取向;而对于富Al的B2 Fe-Al合金,P2峰则产生于应力诱导下Al反位置原子在Fe空位之间的运动.     

Effects of aging on the phase transformation and sintering properties of TiO2 gels

Several research results suggest the binding energy of carbon–vacancy (C–V) complexes is of the order 35–55 kJ/mole in face-centered cubic (fcc) iron-base alloys. In addition to point-defect anelasticity, we examine data on self-diffusion of Fe in fcc Fe, which are quantitatively consistent with our results on point-defect structure modeling. Quenching, cold work, and electron irradiation increase the height of damping peaks associated with C motion, consistent with a contribution of C–V complexes to the relaxation strength of these peaks. The effect of increasing C content on self-diffusion of Fe in fcc Fe is to decrease the activation energy for self-diffusion, hence increase the diffusivity, and implies a C–V binding energy of 40 kJ/mol. We have used first-principles gradient-corrected density functional calculations to determine directly the binding energy of nearest-neighbor C–V pairs in fcc iron. A value of 35 kJ/mol is obtained.     

Thermal decomposition study of electrodeposited Fe-C and Fe-Ni-C alloys by differential scanning calorimetry

Fe-0.96mass%C and Fe-15.4mass%Ni-0.70mass%C alloys with hardness of 810 and 750 HV respectively have been electrodeposited at 50°C from sulphate based baths containing a small amount of citric acid and L-ascorbic acid. Differential scanning calorimetry of the electrodeposited samples has been carried out in the temperature range of 293–725 K in argon atmosphere. Electrodeposited pure Fe is also investigated for comparison purposes. The DSC curves of both alloys contain two exothermic peaks: at about 411 K and 646 K for the Fe-C alloy, and 388 K and 639 K for the Fe-Ni-C alloy. These peaks are irreversible and do not appear during a second thermal cycling. The lower temperature peaks (designated as I) have been attributed mainly to the formation of /-Fe₂C (first stage of tempering), while the higher temperature peaks (designated as III) are ascribed predominantly to -Fe₃C formation (third stage of tempering). The presence of these peaks in the DSC curves confirms that electrodeposited Fe-C and Fe-Ni-C alloys are in a metastable state, where carbon atoms are entrapped in the iron lattice. The decomposition sequence of electrodeposited Fe-C and Fe-Ni-C alloys is found to follow the same general pattern as that of thermally prepared martensite. Attempt has been made to estimate the activation energy values for the reactions associated with the DSC peaks of the electrodeposited alloys and these values are compared with the available data on thermally prepared martensite.     

Effect of iron on the solubility of hydrogen in tantalum

Pressure-composition-isotherms for Ta–Fe–H systems have been investigated in the temperature range 673–873 K. Tantalum–iron alloys (Ta–xFe, x = 0, 1.6 and 3.2 atom  % Fe) were prepared by arc melting using high purity elements. The equilibrium solid solubility of hydrogen in the alloys decreases with an increase of iron content. Thermodynamic parameters of the solution process—the Gibb’s free energy, enthalpy, and entropy, for each of the solutions have been calculated. The relative partial molar enthalpy becomes less negative with increase in iron content, whereas the entropy values are nearly constant for these alloys. The solubility changes were explained on the basis of change in lattice strain energy of tantalum due to iron addition.     

Analytical electron microscopy of aluminium alloys

X-ray microanalysis and electron energy loss spectroscopy of thin foils constitute the important techniques of high resolution chemical analysis using the electron microscope. The technique of x-ray microanalysis is discussed in this paper with particular emphasis on the study of aluminium alloys using a dedicated scanning transmission electron microscope (stem). The principle of determining chemical composition from observed x-ray peak intensities including the absorption of x-rays and beam broadening in thin foils are considered. The accuracy of peak intensity measurement and detection limits in x-ray microanalysis are illustrated with reference to Al-Mn alloys. The Cliff-Lorimer (k) factors for manganese, iron and copper with respect to aluminium were obtained from standard samples. Identification of phases in 1100 and 1200 aluminium and 3008 (Al-Mn-Zr) alloy were carried out from measured intensities of x-ray peaks. The experimental results emphasize the value of developing techniques for extracting the particles from the aluminium matrix. The transition phases formed in Al-6%Zn-3%Mg and Al-4% Cu were investigated by micro-diffraction and x-ray microanalysis.     

铁基合金中以氏体均匀形核热力学探讨

根据马氏体相变的经典形核理论,重新对铁基合金是马氏体相变的形核过程进行了热力学估算,结果表明,均匀形核的临界形核功比热能低一个数量级。这意味着铁基合金中的马氏体相变形核可由热起伏来促发。对早期的小颗粒实验以及铁基体材料中马氏体相变的相关实验结果进行了分析讨论,表明均匀形核机制和这些实验结果相一致。     

Fe-Al合金内耗特征研究进展

原子缺陷对Fe-Al合金的力学和物理性能有重要影响,而内耗是对原子缺陷运动非常敏感的物理量.通过内耗特征的考查可以了解Fe-Al合金中原子缺陷的运动变化规律.对Fe-Al合金的内耗特征进行了分析,在总结与原子缺陷有关的3个内耗峰的主要特征和形成机理的基础上分析了以往研究中存在的争议和不足,并对今后的研究提出了建议.     

铁基合金中马氏体形核动力学探讨

根据马氏体相变的经典形核理论,重新估算了铁基合工中马氏体均匀形核激活能,研究了激活能与界面能和相变驱动力的关系。结果表明,热激活形核具有很低的形核激活能,热激活能形核动力学与马氏体形核动力学实验研究结果一致,在动力学研究的基础上,提出了马氏体相变的形核机制,在形核机制中,除了热激活菜核,还考虑了应力对马氏体形核的作用,特别是在低温时由于急应内应力对形核的贡献。     

Examination of the specific features of the electron density of states of weakly nonstoichiometric Fe–V–Al alloys through the analysis of low-temperature heat capacity

The results of a comparative study of low-temperature heat capacity and resistivity of weakly nonstoichiometric Fe–V–Al alloys with their composition varied (in iron, vanadium, and aluminum atoms individually) with respect to the stoichiometric Fe₂Val alloy are reported. The electron density of states near the Fermi energy is estimated for the studied alloys. The data confirming the presence of a narrow pseudogap at the Fermi level in alloys enriched with vanadium and the lack of such a pseudogap in alloys enriched with iron or aluminum are obtained.