热电池阳极材料Li-B合金的密度分析

根据LiB化合物的六方结构模型,计算了热电池阳极材料Li-B合金随B含量变化理论密度曲线,采用阿基米德方法分别测量了24％B(摩尔分数)Li-B合金反应完全并经冷挤压样品和未经第二次放热反应中间样品的密度,综合分析了以往不同研究者测量的结果,研究表明,反应充分并消除合金中孔隙后其实验密度值与理论计算一致,以往造成实验偏差的主要原因是样品中存在孔隙,中间样品的密度与Li-B元素混合计算密度一致,它支持在第一次反应和第二次反应之间B溶化在Li中的观点。     

硼粉粒度对Li-B合金结构及热稳定性的影响

分别以3种粒度的硼粉为原料,采用相同的成分配比和工艺参数熔炼制备Li-B合金铸锭。合金铸锭经挤出和轧制获得薄带。随后进行X射线衍射(XRD)测试、扫描电子显微镜(SEM)观察、化学成分分析和热稳定性测试。XRD结果显示,Li-B合金由Li_7B_6相和锂相组成,且Li_7B_6相与锂相的衍射峰强度比随硼粉粒度的增大而减小。SEM观察表明,随原料硼粉粒度的增大,Li-B合金的纤维组织变得粗大且不均匀。化学成分测试显示,Li-B合金中化合态硼含量随硼粉粒度的增大而减小。热稳定性测试表明,原料硼粉的粒度越大,Li-B合金的热稳定性越差。     

BaZrO_3耐火材料与锆合金熔体的界面反应机理探究

使用BaZrO_3坩埚真空感应熔炼了Zr-4合金,采用SEM、EDS、XRD等方法分析了坩埚与合金熔体间的界面反应并对反应机理进行探究。结果表明,熔炼后BaZrO_3坩埚结构依旧完整,合金熔体与BaZrO_3耐火材料间发生一定程度的润湿,但坩埚与合金间未观察到明显的界面反应层,仅存在约20μm的渗透层。     

钛合金熔炼用AZrO3（A=Ba,Sr,Ca）坩埚的制备及其使用性能研究

综述了3种新型复合氧化物(CaZrO3、SrZrO3和BaZrO3)坩埚的制备工艺,分析了3种坩埚熔炼TiNi合金后的效果和界面反应情况。合金熔体与耐火材料间无元素扩散,3种耐火材料均对合金熔体具有良好的反应惰性。此外,通过对比3种耐火材料坩埚与熔体间的界面反应层厚度,发现BaZrO3对TiNi合金熔体具有最高的化学稳定性。进一步使用BaZrO3制备成工业用25kg级坩埚并熔炼TiNi、TiFe、TiAl铸锭,发现铸锭杂质含量较低,说明BaZrO3是一种极具潜力的钛合金熔炼用新型耐火材料。     

CuSn合金熔体结构变化及其对凝固行为和组织影响

运用电阻法和DSC热分析发现了CuSn30%合金熔体中存在不可逆的结构转变。在转变区间前后,通过熔体过热处理手段探索了这一结构变化对合金凝固过程及凝固组织的影响。结果表明,不可逆熔体结构的变化导致熔体凝固所需的过冷度增大,合金凝固组织变化明显,初生相和共析组织细化,分布弥散化。并从熔体结构转变角度对上述现象的作用机理进行了分析探讨。     

探析熔体过热处理对亚共晶Al-Si合金凝固特性和组织的影响

文章将亚共晶Al-Si合金为研究对象,分析熔体过热处理对其凝固特性与组织的影响,在实验室配制Al-Si合金,对其进行熔体过热处理实验,分析不同实验条件下,Al-Si合金的凝固组织变化。     

Fe-Si-B-P-C熔体性质对非晶薄带质量的影响

分别采用振荡杯法和座滴法研究了Fe-Si-B-P-C合金体系熔体黏度及表面张力随温度的变化规律,确定了黏度的温度敏感性差异最大的2个合金成分。用平面流工艺制备了该2种合金的非晶薄带,分析了薄带的厚度和贴辊面表面质量随熔体温度的变化。结果表明,非晶薄带的厚度随熔体温度的升高而近似线性减小;对于熔体黏度对温度不敏感的合金来说,熔体温度变化对薄带厚度的影响也相对较小;薄带贴辊面的气坑尺寸和数量均随熔体温度的升高先减小(减少)后增大(增多)。最后,分别从黏度及表面张力对熔潭的影响角度对实验结果进行了分析。     

人造金刚石触媒材料

文章报导了以Ni为基的NiMnCo触媒合金的制备工艺特点,合理选择,成分最佳化 由于材料使用稳定,从而使合成金刚石效果显著。合金结构符合触媒对应原理。测试了合金的物理、化学、电阻和一些热物理常数等。对合金熔体的合成片相变进行了研究。熔体高温溶碳与传压介质、合金元素反应和相互作用引起成分变化。观测结果表明、熔体组织为铸态,呈多相结构:基本是奥氏体;球状石墨含有多种微量元素,它都被一层薄膜包围;金刚石有薄层,它可分为三个亚层,而亚层中的碳及铁含量不同。对晶体薄层进行了讨论。指出,金刚石薄层是伸向再结晶石墨,薄化了基体部分奥氏体。     

铝—硼中间合金的研制及应用

本文采用铝热还原法生产铝-硼中间合金。合适的生产工艺应该采用氟硼酸钾为含硼原料,与铝液反应,通过控制反应温度、改变加料方法,加钛剂对熔体进行处理。能够生产出流动性好、易浇注、硼化效果良好的铝—硼中间合金     

铝合金制造方法

正美国专利6132532本专利介绍了一种生产Al-Si铸造合金的生产方法。该工艺步骤如下:将合金加热到浇铸Tp温度(液相温度与750℃之间的温度);添加变质剂,变质剂为超细粉末,它可在Al-Si铸造合金加工过程中保持固相形态;将合金熔体过热到第二温度,第二温度为液相到1100℃之间的温度,第二温度保持时间为20~30min;再冷却到750℃进行浇铸。     

Dissolution of reactive strontium-containing alloys in liquid aluminum and A356 melts

The dissolutions of commercial purity strontium and a 90 pct Sr-10 pct Al alloy in liquid aluminum and A356 alloys has been investigated. The dissolutions of these alloys was found to be accompanied by the formation of various intermetallic compounds, the type of which depends on the chemistry and temperature of the melt. Additions at low melt temperatures resulted in the exothermic formation of those intermetallics that have the lowest strontium contents, as seen in the relevant phase diagram,i.e., Al₄Sr in liquid aluminum and SrAl₂Si₂ in liquid A356. Due to low reaction rates at these temperatures, these intermetallics formed as dispersed particles that could easily dissolve in the melt, yielding high recoveries. At high melt temperatures, the associated chemical reactions yielded, as products, the higher strontium intermetallics, which formed with little or no exothermicity. These compounds were observed to be scarcely soluble in the melt, resulting in low recoveries. The dissolution time of these alloys were found to show good agreement with calculated values based on a two-stage model comprising an initial exothermic reaction period and a subsequent free dissolution period. In general, the high-strontium alloys were determined to be efficient at low melt temperatures of 675°C to 700°C. These reactive alloys were observed to form thick surface scales in air, which, in the case of commerical purity strontium, proved to be detrimental to dissolutions because they formed a barrier between the solid and the liquid.     

Two-stage electrochemical synthesis of double molybdenum carbides

A new two-stage synthesis of double molybdenum and nickel carbides and high-activity and stable catalytic coatings of nickel-promoter molybdenum carbides in salt melts is developed. The first stage includes the formation of molybdenum-nickel alloys by an electrolytic method and currentless transfer in chloride melts. The second stage consists in the carbonization of the alloys in a chloride-carbonate melt under various synthesis conditions. The stabilities of the nickel-promoter catalytic systems are studied, and their catalytic activities in the back water-gas shift reaction are determined.     

X-Ray Videomicroscopy Studies of Eutectic Al-Si Solidification in Al-Si-Cu

Al-Si eutectic growth has been studied in-situ for the first time using X-ray video microscopy during directional solidification (DS) in unmodified and Sr-modified Al-Si-Cu alloys. In the unmodified alloys, Si is found to grow predominantly with needle-like tip morphologies, leading a highly irregular progressing eutectic interface with subsequent nucleation and growth of Al from the Si surfaces. In the Sr-modified alloys, the eutectic reaction is strongly suppressed, occurring with low nucleation frequency at undercoolings in the range 10 K to 18 K. In order to transport Cu rejected at the eutectic front back into the melt, the modified eutectic colonies attain meso-scale interface perturbations that eventually evolve into equiaxed composite-structure cells. The eutectic front also attains short-range microscale interface perturbations consistent with the characteristics of a fibrous Si growth. Evidence was found in support of Si nucleation occurring on potent particles suspended in the melt. Yet, both with Sr-modified and unmodified alloys, Si precipitation alone was not sufficient to facilitate the eutectic reaction, which apparently required additional undercooling for Al to form at the Si-particle interfaces.     

Reoxidation of Ni‐ and Ni‐Fe‐Alloys by Al2O3‐SiO2 Refractory Materials

Reactions at the refractory/melt interface during ingot casting of Ni‐ and Ni‐Fe‐alloys were studied. The casts were performed using different alumino‐silicate bricks as refractory materials. Samples taken from the casting channel before and after casting were investigated using light and scanning electron microscopy with XPS. Thermodynamic calculations were performed with FactSage and the results were compared with the results from industrial tests. After the melt has infiltrated the surface layer of the bricks, refractory corrosion starts with an attack of Mn and Mg of the melt on SiO₂ and Fe₂O₃ of the refractory bonding matrix. Despite the presence of elements with higher oxygen affinity in the melt, low‐melting alumino‐silicate phases are predominantly built by the reaction with Mn and Mg. In a second step this liquid phase either traps non‐metallic inclusions from the melt or, at higher contents of Zr, Ti, Mg, Y etc. in the melt, causes massive reoxidation and inclusion formation. The refractory materials investigated show an increasing trend for reoxidation with an increasing amount of SiO₂ in glassy phases of the refractory bonding matrix. By the use of a refractory material with higher mullite content in the bonding matrix or by use of alumina bricks a strong reoxidation of the melt and intense inclusion formation can be avoided. These observations are also valid for other alloys with higher contents of elements with high affinity to oxygen.     

Dissolution of solid copper cylinder in molten tin-lead alloys under dynamic conditions

The dissolution of a copper cylinder in molten tin-lead alloys was studied at 673 K under static and dynamic conditions in the peripheral velocity range 1.9 to 75.4 cm per second using an immersion method. The dissolution rate of copper increased with increasing tin concentration and peripheral velocity. The solution rate constant increased with peripheral velocity and with diffusion coefficient of copper in the melt. The constant decreased with kinematic viscosity of the melt and diameter of the specimen. The dissolution of copper in molten tin-lead alloys was mixed control. Flow of the melt under forced convection was turbulent flow with Taylor vortices. Natural convection occurred in dissolution of stationary copper in tin rich alloys due to hydrodynamic instability from density differences in the melt. YOSHIFUSA SHOJI, formerly Graduate Student, Tokai University, Tokyo     

Solubility of nitrogen in liquid nickel and Ni‐Cr alloys under elevated pressure

The present work focuses on the experimental evaluation of the solubility of nitrogen during the melting process in nickel and binary Ni‐Cr alloys under elevated nitrogen partial pressure at 1550°C. In order to estimate the attainable nitrogen concentrations, the solubility of nitrogen in dependence of melt temperature and nitrogen partial pressure has been calculated by using Thermo‐Calc. Thermo‐Calc supported predictions of the achievable nitrogen contents referring to the investigated alloys show good agreement with the experimental data only up to nitrogen partial pressures of 0.1 MPa. The applicability of Sieverts law has been examined for nitrogen partial pressures up to 6 MPa and Ni‐Cr alloys with chromium mass contents of 15, 20, 30, 40 and 50 %. A deviation from Sieverts law was observed for the alloys with chromium mass contents higher than 20 % and a nitrogen partial pressure above 0.1 MPa. The effect of chromium and the nitrogen partial pressure on the solubility of nitrogen is described in terms of the Wagner's first and second order interaction parameters.     

AlTiC中间合金制备过程中TiC的形成机制

使用氟钛酸钾、石墨与铝制备AlTiC中间合金。用扫描电镜和透射电镜分析了TiC粒子在制备过程中不同阶段的形态。在TiC生成热力学条件的研究基础上，提出了K2TiF6与石墨在铝液中的直接反应是TiC粒子的主要形成机制。     

Electrode Process of Y~(3 )Ion on Molybdenum and Nickel Electrodes in YCl_3-NaCl-KCl Melt

The electrode process of Y~(3 )ion on molybdenum and nickel electrodes has been studied by cyclicvoltammetry and chronopotentiometry in the YCl_3-NaCl-KCl melt.The overall charge transfer process is atwo-step reaction:Y~(3 ) e=Y~(2 );Y~(2 ) 2e=Y.Yttrium reduced on the nickel electrode can form a series of Ni-Yalloys.X-ray diffraction analysis was employed to determine the alloy compositions formed under different con-ditions.     

Rate of reduction of Cr2O3 by carbon and carbon dissolved in liquid iron alloys

The rate of reaction of Cr₂O₃ with carbon or carbon dissolved in liquid iron alloys, and the decarburization of Fe-Cr-C alloys in Ar-O₂ gas mixtures has been investigated. The rate of reduction of dense Cr₂O₃ on the surface of Fe-Cr-C alloys was controlled by the diffusion of carbon to the surface of the melt. The chemical diffusion coefficient derived from the results (8.5 × 10^-5 cm²/s) is in agreement with previous work. The decarburization of Fe-Cr-C alloys in Ar-O₂ gas mixtures was apparently carried out by the Cr₂O₃ which formed on the surface of the melt by the reaction of the dissolved Cr with the oxygen gas and the rate of decarburization was controlled by the diffusion of carbon to the surface. The rate of reduction of Cr₂O₃ by various types of carbon was also investigated at temperatures from 1300 to 1600°C; the initial rate appears to be controlled by gas phase mass transfer of the CO away from the surface of the reactants.     

Inhibited coarsening of a spray-formed and extruded hypereutectic aluminum-silicon alloy in the semisolid state

The microstructural evolution of a spray-formed and extruded hypereutectic aluminum-30 pct silicon-5 pct copper-2 pct magnesium alloy heated into the semisolid state has been investigated. Liquid is formed initially by a quaternary eutectic reaction and then by a ternary melt reaction. These reactions occur relatively quickly. However, the binary Al-Si eutectic melt reaction takes a significant time—around several hours depending on the temperature. The coarsening rate constants (K) for the growth of the silicon particles are approximately three to four orders of magnitude lower than those for the majority of metal spray-formed alloys. This may be associated with difficulties in addition or removal of atoms from the low index silicon facets. Where growth does occur, agglomeration of silicon particles may play a large role, especially at higher liquid contents. Electron backscatter diffraction (EBSD) gives evidence of agglomeration, and furthermore shows that high-angle silicon-silicon boundaries are not wetted with liquid.