KCl熔体中钬离子在钴电极上的还原

用循环伏安法、恒电位电解断电后的电位─时间曲线、电位阶跃下的电流─时间曲线以及Ｘ─射线衍射法研究了在ＫＣｌ─ＨｏＣｌ３熔体中Ｈｏ３＋在钴电极上还原的电极过程。Ｈｏ３＋在钴电极还原时，在形成金属间化合物Ｈｏ２Ｃｏ１７等后才析出纯金属钬，确定了形成Ｈｏ２Ｃｏ１７这一步是可逆的。测定了Ｈｏ２Ｃｏ１７等五种金属间化合物的生成自由能和Ｈｏ原子在Ｈｏ２Ｃｏ１７中的扩散系数及扩散活化能。     

Electroreduction of Ho~(3 ) on Nickel Cathode in Molten KCl-HoCl_3

The holmium metal can be prepared bymolten salt electrolysis with high consumptionof electric energy and low recovery of holmiumat the high electrolytic temperature. As weknow, the electrolytic temperature would bedecreased, provided rare earth alloy was prepared by electrolysis. We are interested in investigating the preparation of Ho-Fe, Ho-Co,Ho-Ni and Ho-Cu alloys by molten salt electrolysis on consumahle transition metal cathodes and the mechanism of forming alloys so asto provide scie…     

Preparation of a Nickel–Holmium Alloy Coating in an Equimolar HoCl<Subscript>3</Subscript>-Containing NaCl–KCl Melt

Cyclic voltammetry is used to study the electrolytic reduction of holmium ions on a nickel electrode in a holmium chloride-containing equimolar molten mixture of sodium and potassium chlorides in a temperature range of 1073–1173 K. The potentials of formation of nickel–holmium intermetallic compounds (IMCs) are determined. Nickel–holmium intermetallic compounds are synthesized by controlled potential electrolysis. Under the selected electrolysis conditions, the prepared coating is shown to be single-phase and its composition corresponds to the HoNi₂ stoichiometry. The coefficients of reaction diffusion of holmium in nickel are calculated and the activation energy of alloy-formation process is determined.     

The Electrochemical Formation of Ni-Tb Intermetallic Compounds on a Nickel Electrode in the LiCl-KCl Eutectic Melts

The work presents an electrochemical study on the formation of Ni-Tb intermetallic compounds in the LiCl-KCl-TbCl₃ melts on tungsten and nickel electrodes at 773 K (500 °C) by electrochemical techniques. For a tungsten electrode, cyclic voltammetry and square-wave voltammetry showed that the electrochemical reduction of Tb(III) proceeded in a one-step process involving three electrons at ?2.06 V (vs Ag/AgCl). For a nickel electrode, the reduction potential of Tb(III)/Tb was observed at more positive values than those on W electrode by cyclic voltammetry, due to the formation of Ni-Tb intermetallic compounds. Square-wave voltammetry and open-circuit chronopotentiometry put into evidence the formation of intermetallic compounds at around ?1.27, ?1.63, and ?1.88 V, respectively. Three alloy samples were obtained by potentiostatic electrolysis on a Ni electrode at various potentials and analyzed by X-ray diffraction, scanning electron micrograph, and energy-dispersive spectrometry. The analysis results confirmed the formation of Ni₁₇Tb₂, Ni₅Tb, and Ni₂Tb alloy compounds.     

Au/Sn界面互扩散特征

从扩散机制、扩散动力学、热力学以及相结构等方面,总结了室温范围内Au/Sn互扩散的主要特点。给出了Au/Sn互扩散中生成的AuSn,AuSn2,AuSn4等金属间化合物的主要性质。详细总结了不同Sn含量的Au/Sn扩散中,初始态、中间态和最终态的金属间化合物的形成次序、形貌、分布、演化等特征。采用热力学方法定量计算了不足量的Au或Sn的条件下Au/Sn扩散中各中间相的生成吉布斯自由能,较好地解释了中间相的演化规律。给出了Au/Sn扩散的扩散数据,以及主要中间相的生长特点,介绍了Kirkendall效应导致的相关效应。     

Cathodic behavior of scandium(III) on reactive copper electrodes in LiF–CaF2 eutectic molten salt

The electrochemical formation of Sc–Cu alloy was investigated in LiF–CaF₂ eutectic molten salt employing various electrochemical methods. Cyclic voltammetry and square wave voltammetry indicate that the reduction of scandium(III) on the tungsten electrode is a one-step reduction process with three electrons transfer. And underpotential deposition of scandium on the copper electrode occurs owing to the depolarization effect, i.e., forming Sc–Cu intermetallic compounds. The thermodynamic properties of the Sc–Cu intermetallic compounds ScCu₄, ScCu₂, and ScCu in the temperature range of 1153–1223 K were estimated by open-circuit chronopotentiometry. Moreover, the Sc–Cu alloys were prepared by potentiostatic electrolysis and characterized by optical microscope, X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results reveal that only Sc–Cu alloy composed of Cu-ScCu₄ can be synthesized at low cathodic current density and above eutectic temperature.     

Y(Ⅲ)在镍电极上电沉积及表面合金化

本文使用循环伏安法,X射线衍射及扫描电镜研究了Y(Ⅲ)在NaCl-KCl-YCl₃熔盐体系,在镍电极上的还原过程。研究结果表明:Y(Ⅲ)在镍电极上还原时,首先形成金属间化合物Ni₅Y及NiY,然后才析出纯金属钇.     

The Effect of Cu Powder During Friction Stir Welding on Microstructure and Mechanical Properties of AA3003-H18

Friction stir welding (FSW) was used to join 3003-H18 non-heat-treatable aluminum alloy plates by adding copper powder. The copper powder was first added to the gap (0.1 and 0.2 mm) between two plates and then the FSW was performed. The specimens were joined at various rotational speeds of 800, 1000, and 1200 rpm at traveling speeds of 70 and 100 mm/min. The effects of rotational speed, second pass of FSW, and direction of second pass also were studied on copper particle distribution and formation of Al-Cu intermetallic compounds in the stir zone. The second pass of FSW was carried out in two ways; in line with the first pass direction (2F) and in the reverse direction of the first pass (FB). The microstructure, mechanical properties, and formation of intermetallic compounds type were investigated. In high copper powder compaction into the gap, large clusters were formed in the stir zone, while fine clusters and sound copper particles distribution were obtained in low powder compaction. The copper particle distribution and amount of Al-Cu intermetallic compounds were increased in the stir zone with increasing the rotational speed and applying the second pass. Al₂Cu and AlCu intermetallic phases were formed in the stir zone and consequently the hardness was significantly increased. The copper particles and in situ intermetallic compounds were symmetrically distributed in both advancing and retreating sides of weld zone after FB passes. Thus, the wider area was reinforced by the intermetallic compounds. Also, the tensile test specimens tend to fracture from the coarse copper aggregation at the low rotational speeds. At high rotational speeds, the fracture locations are placed in HAZ and TMAZ.     

Thermochemistry of alloys of transition metals: Part IV. Alloys of copper with scandium,yttrium, lanthanum,and lutetium

The enthalpies of mixing of liquid copper with liquid lanthanum, and with solid scandium, yttrium, and lutetium have been measured by high temperature reaction calorimetry at 1373 K. After correction for the enthalpies of fusion the limiting enthalpies of solution of the liquid metals in copper are-102 kJ mol^-1 (Sc), —105 kJ mol^-1 (Y), —103 kJ mol^-1 (La), and —120 kJ mol^-1 (Lu). We also report approximate enthalpies of solution of chromium and vanadium in copper; all values are compared with predictions published by Miedema and co-workers. The enthalpies of formation of eight congruent melting intermetallic compounds in the system Cu-Sc, Cu-Y, and Cu-La have been determined. The values are compared with corresponding data for the liquid alloys; this comparison provides approximate enthalpies and entropies of fusion for the intermetallic compounds. It is found that these entropies of fusion average 1. 1R to 1.2R,i.e., the values are comparable to those found for close-packed cubic metals. This indicates that the disordering of the two atoms probably contributes little to the entropies of fusion of the compounds.     

Influence of Nb and Cu Elements on the Intermetallic Particles Morphology in Ti/Al Multilayer Composite Processed Through Hot Pressing and Rolling

Ti–Al–Nb composites were produced by solid state diffusion bonding through hot pressing and rolling followed by annealing at 700 °C for 0.5, 1, 1.5 and 2 h. The morphologies of TiAl₃ intermetallics were investigated by Scanning Electron Microscopy combined with Energy-dispersive X-ray spectroscopy. Titanium tri-aluminide (TiAl₃) particles with blocky morphology were dispersed into Aluminum matrix. In the presence of niobium and copper, TiAl₃ particles were produced in different sizes and morphologies. The presence of Nb in the composite led to the formation of irregular angular morphology, while the copper resulted in cubic morphology of the intermetallic particles. The EDS results indicated that TiAl₃, (Ti, Nb)Al₃ and (Ti, Nb, Cu)Al₃ intermetallic compounds appeared near Ti zone, Nb Zone and in the presence of Cu, respectively.     

Electrochemical co-reduction of Y(III) and Al(III) in a fluoride molten salt system and electrolytic preparation of Y–Al intermediate alloys

In this study, a molten salt co-reduction method was proposed for preparing Y–Al intermediate alloys and the electrochemical co-reduction behaviors of Y(III) and Al(III) and the reaction mechanism of intermetallic compound formation were investigated by transient electrochemical techniques. The results show that the reduction of Y(III) at the Mo electrode is a reversible electrochemical process with a single-step transfer of three electrons, which is controlled by the mass transfer rate. The diffusion coefficient of Y(III) in the fluoride salt at a temperature of 1323 K is 5.0238 × 10^?3 cm²/s. Moreover, the thermodynamic properties associated with the formation of Y–Al intermetallic compounds were estimated using a steady-state electrochemical method. Y–Al intermediate alloy containing 92 wt% yttrium was prepared by constant current electrolysis at 1323 K in the LiF–YF₃–AlF₃–Y₂O₃ (6 wt%)–Al₂O₃ (1 wt%) system at a cathodic current density of 8 A/cm² for 2 h. The Y–Al intermediate alloy is mainly composed of α-Y₂Al and Y phases. The development and application of this innovative technology have solved major technical problems, such as a long production process, high energy consumption, and serious segregation of alloy elements at this stage.     

Phase and structural transformations in production of powders of intermetallic compounds

The mechanism and kinetics for the formation processes of powders of intermetallic compounds when the mixtures of oxides, metals, and calcium hydride are heated in the range t = 900–1200°C (the calcium hydride method) are investigated. It is established experimentally that the compounds are synthesized in two stages. At the first stage, metal oxides are reduced by the calcium melt (starting from ∼840°C); at the second stage, diffusion interactions of the components proceed. It is shown that, for the effective development of processes of alloy formation, metal components should be dissolved in liquid calcium or to form the eutectics between one another at a value of t not exceeding the working temperature of the process. As the latter increases, the reduction of oxides and diffusion interaction between the components are intensified and finished at t < 1200°C with the formation of homogeneous powders of intermetallic compounds. The possibility of forming a wide nomenclature of powders for intermetallic compounds of different applications is shown.     

High cycle fatigue life improvement of polycrystalline alpha-iron modified by silver,chromium, aluminium,and yttrium ion implantation

HCF tests on polycrystalline alpha-iron with and without silver, chromium, yttrium, and aluminum ion implantation have been conducted. The stress-life curves obtained were best fit by using the power function. It was shown that the fatigue property had been improved to different extent after ion implantation. Enhanced strengthening of the implanted layer due to radiation induced defects, super solid solution, and formation of intermetallic compounds in implantation was the prominent mechanism for property improvement.     

Thermochemistry of binary alloys of transition metals: The Me-Sc,Me-Y,and Me-La (Me = Ag,Au) systems

The enthalpies of mixing of the alloys of silver and gold with scandium, yttrium, and lanthanum have been measured by high-temperature reaction calorimetry at 1473 K. The standard enthalpies of formation of nine congruently melting intermetallic compounds in these systems (AgSc, Ag₂Sc, AgY, Ag₅₁Yi₁₄, AgLa, Ag₅₁La₁₄, AuSc, AuY, and AuLa) also have been determined. All values are compared with the predictions of the semiempirical model of Miedema and co-workers.^[14] A comparison between the data for the liquid alloys and for the intermetallic compounds provides approximate enthalpies and entropies of fusion for the considered compounds. Associate Professor, is on leave from his permanent position at the Institute of Metals Research, Polish Academy of Sciences, 30-059 Krakow, Poland     

纳米Cu-Sn金属间化合物的制备及形成机理

以CuCl2.2H2O和SnCl2.2H2O为原料,NaBH4为还原剂,采用溶剂热法制备Cu10Sn3、Cu3Sn和Cu6Sn5金属间化合物。利用XRD、TEM、SAED对产物的物相、形貌及结构进行表征,考察了溶剂及原料配比对Cu-Sn金属间化合物形成的影响。结果表明,制备的三种产物颗粒尺寸分别为100~150nm、150~200 nm和300 nm;合金化进程是通过原子间相互吸附与扩散实现;反应初始阶段生成Cu10Sn3和Cu3Sn,其中Cu10Sn3是亚稳态,易转变为Cu3Sn。随着反应的继续进行,由于Sn原子不断向Cu3Sn扩散而最终形成Cu6Sn5。     

Impurity controlled diffusion reaction in thorium-vanadium system

The effect of ppm level impurities present in the thorium metal on the diffusion reaction in thorium-vanadium system has been investigated by making “sandwich” type diffusion couples and annealing them in the temperature range of 900 to 1200°C. The microstructure of the diffusion zone has been examined by optical and electron microscopy. X-ray powder techniques have been employed to detect the presence of secondary intermetallic phases in thorium metal and in the diffusion zone. The chemical composition of these phases and the elemental distribution in the diffusion zone have been established by using an electron microprobe analyzer. The time and the temperature dependence of the diffusion zone width is used to evaluate the kinetics of layer growth. Present studies have shown that impurities like iron, copper and aluminum form low melting point intermetallic compounds in thorium metal and segregate at the grain boundaries. Further in a diffusion reaction at the elevated temperatures, these thorium rich secondary phases melt and form a liquid film between the thorium and the bonding metal, vanadium in the present case. The rate controlling process appears to be an interfacial chemical reaction involving dissolution of vanadium in the thorium rich liquid.     

Thermodynamics of rare earth metal interaction with copper

The change in thermal and thermodynamic properties along the isoformula series of rare earth metals (R) compounds with copper is analyzed. It is shown that in binary R-Cu systems the maximum thermal effects of formation are observed for the most refractory and congruently melting intermetallic compounds. In the liquid state they are observed at concentrations that are close to the composition of these compounds. It is noted that in contrast to other R scandium on reaction with copper behaves as a d-metal. __________ Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 36–43, March–April, 2006.     

Electrochemical behavior of Dy(Ⅲ) on bismuth film electrode in eutectic LiCl-KCl melts

An electrochemical study of dysprosium(III) on Bi film electrode was carried out in eutectic LiCl-KCI melts by transient and steady state electrochemical techniques.The results of transient electrochemical techniques showed that the reduction of Dy(III) appears at a more positive value than the one detected on W electrode owing to the formation of Bi-Dy intermetallic compounds through electrochemical deposition of Dy on bismuth film electrode.The thermodynamic properties of the formation for Dy-Bi intermetallics were estimated by a steady state electrochemical method in a temperature range of 713-803 K.Furthermore,the electrochemical preparation of Bi-Dy alloys was conducted by galvanostatic electrolysis at different current intensities.The Bi-Dy alloys,characterized by scanning electron microscopy equipped with energy dispersive spectrometry and X-ray diffraction,are comprised of DyBi_(3/5) and DyBi phases.     

Kinetics of growth of the Ti-Co

The growth behavior of the disordered and ordered intermetallic compounds in the Ti-Co system from undercooled melts during rapid solidification has been studied in detail. It was found that cooling rates of the order of 10¹⁰ to 10¹² K s^-1 were insufficient to suppress the nucleation and growth of the intermetallic compounds. The compound isomorphous to Ti₂Co does not exhibit faceting, indicating a nonsingular crystal/liquid interface morphology at high growth velocities. While a TiCo-like compound was found to have a ordered bcc structure, the formation of even the disordered TiCo₃ was completely suppressed by the high isothermal velocities, leading to glass formation. The growth velocity of compounds formed in the composition range 23.3 to 59.7 at. pct Co was found to be diffusion limited with nucleation times smaller than the total melt lifetimė in the process. The overall glass formation range was found to be very small, although the equilibrium phase diagram shows the presence of a variety of intermetallic compounds.     

Electrochemical behavior of Dy(III) on bismuth film electrode in eutectic LiCl-KCl melts

An electrochemical study of dysprosium (III) on Bi film electrode was carried out in eutectic LiCl-KCl melts by transient and steady state electrochemical techniques. The results of transient electrochemical techniques showed that the reduction of Dy (III) appears at a more positive value than the one detected on W electrode owing to the formation of Bi-Dy intermetallic compounds through electrochemical deposition of Dy on bismuth film electrode. The thermodynamic properties of the formation for Dy-Bi intermetallics were estimated by a steady state electrochemical method in a temperature range of 713–803 K. Furthermore, the electrochemical preparation of Bi-Dy alloys was conducted by galvanostatic electrolysis at different current intensities. The Bi-Dy alloys, characterized by scanning electron microscopy equipped with energy dispersive spectrometry and X-ray diffraction, are comprised of DyBi_3/5 and DyBi phases.