Ga-In共晶固定点复现及赋值研究

次级固定点进一步分度温度计应用于温度校准已成为减小温度量值传递不确定度的重要方法.围绕Ga-In二元合金,以高复现水平为目标,详细介绍了大尺寸固定点容器研制、固定点灌注过程,开展了固定点复现性、亚配比剩余镓温坪验证实验研究;采用了切线交点法、均值法、三次多项式拟合法3种相变温度取值方法对Ga-In固定点进行了评价和分析...     

A Concerted International Project to Establish High-Temperature Fixed Points for Primary Thermometry

Research into high-temperature fixed points above 1,100°C has made significant progress since they were first reported in 1999. In particular, it has been established that single cells are repeatable at the sub-50 mK level, and intra-cell reproducibility at the 100 mK level has been demonstrated even at temperatures as high as 2,500°C. The fixed points have been used to compare temperature and radiometry scales over a wide temperature range, and are being developed and established as secondary references for thermocouple calibrations. However, before they can be fully accepted as primary temperature references, much work remains to be done, namely: (1) Establishment of long-term stability of the fixed-point temperature; (2) Development of robust procedures for the reliable construction of the fixed-point cells (to ensure routine intra-cell reproducibility of 100 mK); (3) Demonstration of long-term robustness of the fixed-point cells; (4) Assignment of thermodynamic temperatures to a selected set of fixed points; (5) Agreement and acceptance of these temperature values by the CCT; (6) Agreed methods on how to take full utility of these new fixed points into any future International Temperature Scale (ITS)—or the current ITS-90 via an addendum to the mise en pratique for the definition of the kelvin. To ensure that this work progresses to completion in a reasonable time frame, a research project, under the auspices of the CCT-WG5, has been formulated and is currently in progress with the aim of achieving the above mentioned targets by 2012. This article will describe this project and detail partner contributions.     

Fe-C共晶点的复现与温坪特性的研究

在温度量传体系中,铜凝固点(1084.62 ℃)以上目前还没有其他纯金属固定点,而金属-碳共晶点作为新兴的固定点具备良好的复现性,可补充铜点以上的温度固定点,拓展现有的高温温度量值传递水平。尽管Fe-C共晶点非常接近铜凝固点,但其仍有较高的使用价值,可为更高温共晶点灌注及复现提供宝贵的经验。用一等标准S偶对Fe-C共晶点的温坪进行测量,其共晶点温度为1152.4 ~1152.5 ℃。     

Development of Gallium and Gallium-Based Small-Size Eutectic Melting Fixed Points for Calibration Procedures on Autonomous Platforms

Melting/freezing temperature curves are studied for the single-component Ga and bimetallic eutectic alloys Ga–In, Ga–Sn, Ga–Zn, and Ga–Al in small-size cells. These phase-transition studies were conducted at VNIIOFI in order to design small-size fixed-point devices for metrological monitoring of temperature sensors on autonomous (e.g., space borne) platforms. The results show that Ga and some Ga-based eutectic alloys in small cells can be used as melting fixed points. The repeatability of melting temperatures of Ga, Ga–In, Ga–Sn, and Ga–Zn fixed points is studied. The effects of the concentration of the second element of Ga-based eutectic alloys and the thermal history on the melting plateau’s shape and the melting temperature are studied.     

Use of Eutectic Fixed Points to Characterize a Spectrometer for Earth Observations

A small palm-sized, reference spectrometer, mounted on a remote-controlled model helicopter is being developed and tested by the National Physical Laboratory (NPL) in conjunction with City University, London. The developed system will be used as a key element for field vicarious calibration of optical earth observation systems in the visible-near infrared (VNIR) region. The spectrometer is hand held, low weight, and uses a photodiode array. It has good stray light rejection and wide spectral coverage, allowing simultaneous measurements from 400 to 900 nm. The spectrometer is traceable to NPL’s primary standard cryogenic radiometer via a high-temperature metal-carbon eutectic fixed-point blackbody. Once the fixed-point temperature has been determined (using filter radiometry), the eutectic provides a high emissivity and high stability source of known spectral radiance over the emitted spectral range. All wavelength channels of the spectrometer can be calibrated simultaneously using the eutectic transition without the need for additional instrumentation. The spectrometer itself has been characterized for stray light performance and wavelength accuracy. Its long-term and transportation stability has been proven in an experiment that determined the “World’s Bluest Sky”—a process that involved 56 flights, covering 100,000 km in 72 days. This vicarious calibration methodology using a eutectic standard is presented alongside the preliminary results of an evaluation study of the spectrometer characteristics.     

Ga-In-Sn微型共晶点相变特性研究

以Ga-In-Sn三元合金为研究对象,研制了可用于现场及在线标定的微型Ga-In-Sn共晶点容器,开展了3种不同配比对相变温度和温坪复现影响的研究。结果表明:3种配比的共晶点温坪可持续1.2~2 h,实验的复现性优于4.5 mK,合成扩展不确定度为9.3 mK(k=2),3种配比的共晶点相变温度平均值为10.748 ℃;在相同热工况下Ga-In-Sn合金发生共晶反应的相变温度不受配比的影响;改变合金熔体的降温速率可改变微型共晶点过冷度。     

用于分度热电偶的Co-C高温共晶点的制作和复现性研究

介绍了中国计量科学研究院研制的用于分度热电偶的Co-C高温共晶点,以及使用铂/钯热电偶对共晶点进行的复现测量的结果。实验数据表明,Co-C高温共晶点的熔点复现性已达到了0.03 ℃。Co-C高温共晶点坩埚在1300 ℃以上温度经历了累计时间500 h、110多次的熔化和凝固实验后依然完好。     

Microstructure Characteristics of the Eutectics of Die Cast AM60B Magnesium Alloy

Under the cold-chamber high pressure die casting (HPDC) process, samples were produced with AM60B magnesium alloy to investigate the microstructure characteristics of the eutectics, especially focusing on the constitution, morphology and distribution of the eutectics over cross section of the castings. Attentions were also paid to study the effect of heat treatment on the eutectics in the die castings. Based on experimental analysis using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), it was determined that fully divorced eutectics consisting of α-Mg and β-Mg17Al12 appeared at the grain boundary of the primary α-Mg in the as-cast microstructure. Islands and networks of β-Mg17Al12 phase were observed in the central region of the castings, while the β-Mg17Al12 phase revealed a more dispersed and granular morphology on the surface layer. The two phases ratio β/α in the central region of the castings was approximately 10%, which was higher than that on the surface layer. Besides, the defect bands contained a higher percentage of the eutectics than the adjacent regions. After aging treatment (T6), only α-Mg phase was detected by XRD in the AM60B magnesium alloy, though a small amount of precipitated β-Mg17Al12 phase was observed at the grain boundary. In contrast to the microstructure of die cast AZ91D magnesium alloy under the same T6 heat treatment, no discontinuous precipitation of the β-Mg17Al12 phase was observed in AM60B magnesium alloy die castings.     

Pd-C高温共晶点复现装置研制

主要针对Pd-C高温共晶点复现装置的组成进行介绍,其中包括复现用高温均热炉炉体、温度控制系统、真空泵、充气保护装置、水冷系统、复现用的石墨坩埚、二等B型标准热电偶和Pt-Pd热电偶等。针对石墨坩埚的灌注和共晶点复现过程进行了描述,根据复现的试验数据进行了相应的分析。     

A Mid-IR Pyrometer Calibrated with High-Temperature Fixed Points for Improved Scale Realization to 2,500°C

Glass surface temperature can be measured using a radiation thermometer operating at a mid-IR wavelength, typically the 3–5 μm band, where the glass is opaque. For optical fiber preforms, the temperature measurement requirement may exceed 2,200°C. Scale realization at national measurement institutes at these temperatures is usually carried out at short wavelengths, typically less than 1 μm. The mismatch in wavelength can lead to significant uncertainties when calibrating a radiation thermometer working at 3–5 μm. To overcome this, a narrow band 3.95 μm radiation thermometer has been built that is designed to be used from 1,000 to 2,500°C. It is calibrated by measurement of high-temperature metal–carbon eutectic fixed-points. The instrument is based on silicon lenses, with a liquid nitrogen (LN₂)-cooled InSb detector, and narrow-band interference filter. An anti-reflection coated objective lens/aperture stop focuses onto a field stop giving a 1 mm target, then a collimating lens, and glare stop. All parts visible to the detector, other than the target area, are either at LN₂ temperature or are part of a temperature-stabilized housing. A relay-operated shutter that blocks the field stop is used to subtract the background. The size-of-source effect of the instrument has been measured. Gold-point measurements have been made to assess the stability. The device has been calibrated using high-temperature fixed points. A three-parameter fit has been applied and the resultant scale compared to an ITS-90 realization.     

一种三段加热的立式高温均热炉的研制

介绍了一种用于Fe-C高温共晶点装置复现的三段加热立式高温均热炉, 包括炉体的设计结构、 温度控制系统、 复现用腔体的密封结构设计和冷却水与充气保护系统等. 对炉体温场的测试结果表明: 该炉体能够满足设计的预期要求, 实现Fe-C高温共晶点的复现.     

Modeling of Transient Heat Transfer in Temperature Fixed Points: Indium Cell Design

Laboratoire national de métrologie et d’essais has recently constructed a new device to realize the indium fixed point adiabatically. In parallel, a numerical heat transfer model has been developed as an aid to understanding its thermal behavior. This transient axially symmetric two-dimensional (2D) model simulates the melting process using the apparent specific heat method; the effects of mixing and convection within the liquid phase of indium are not taken into account. The thermal parameters, the nonuniformity of the furnace, and the thermal control of the surroundings were assessed with the aim of reducing parasitic heat exchanges. The results of the modeling are in good agreement with the measurements and clarify the parasitic heat flux observed during the phase transition. This article describes the model and the first results obtained. The model is a helpful tool in evaluating future technical improvements of the enclosure used to realize the indium fixed point.     

Investigation of Furnace Uniformity and its Effect on High-Temperature Fixed-Point Performance

A large-area furnace BB3500YY was designed and built at the VNIIOFI as a furnace for high-temperature metal (carbide)–carbon (M(C)–C) eutectic fixed points and was then investigated at the NMIJ. The dependence of the temperature uniformity of the furnace on various heater and cell holder arrangements was investigated. After making some improvements, the temperature of the central part of the furnace was uniform to within 2K over a length of 40 mm—the length of the fixed-point cell—at a temperature of 2,500°C. With this furnace, the melting plateaux of Re–C and TiC–C were shown to be better than those observed in other furnaces. For instance, a Re–C cell showed melting plateaux with a 0.1K melting range and a duration of about 40 min. Furthermore, to verify the capability of the furnace to fill cells, one Re–C and one TiC–C cell were made using the BB3500YY. The cells were then compared to a Re–C cell made in a Nagano furnace and a TiC–C cell filled in a BB3200pg furnace. The agreement in plateau shapes demonstrates the capability of the BB3500YY furnace to also function as a filling furnace. B. Khlevnoy and K. Anhalt are guest scientists at NMIJ at the time of investigation.     

Co-C共晶点研制及评价

根据国际温度咨询委员会辐射测温工作组(CCT-WG5)对世界各国计量机构开展Co-C共晶点研制工作的相关要求,设计并搭建了Co-C共晶点灌注系统,采用直接共晶法成功灌注了满足复现实验要求的Co-C共晶点坩埚。针对直接共晶灌注法效率低、坩埚破裂风险大的缺陷,提出了对灌注方法的改进方案,并依据该方案成功灌注了2个Co-C共晶点坩埚。对灌注的Co-C-2#共晶点进行了复现试验,结果显示:拐点温度的不确定度为5.3 mK,满足小于10 mK的CCT要求;短期重复性为9.6 mK,满足小于20 mK的CCT要求。     

多元低熔点共晶合金Sn16Bi52Pb32和In21Sn12Bi49Pb18凝固组织和相组成研究

随着环境保护的需要,具有较低Pb含量或不含Pb元素的多元低熔点合金越来越受到工业界的重视和青睐,但是该类合金的组织结构形态、相组成和基本的物理化学数据比较缺乏,不利于其工业化应用。鉴于此,文章对两种具有较低Pb含量的Sn_(16)Bi_(52)Pb_(32)(质量分数)合金和In_(21)Sn_(12)Bi_(49)Pb_(18)(质量分数)合金进行了凝固组织、相组成以及物化性能方面的研究。扫描电镜(SEM)、差示扫描量热法(DSC)、X射线衍射(XRD)等分析测试结果表明:Sn_(16)-Bi_(52)Pb_(32)合金由Bi-(Pb)固溶体相、Sn-(Bi,Pb)固溶体相以及Pb_7Bi_3化合物相组成,具有准规则共晶凝固组织结构。而In21Sn12Bi49Pb18合金由InBi化合物相、PbBi化合物相以及Sn-(Bi,In)固溶体相组成,具有复杂规则的共晶组织形貌。     

NiAl-28Cr-5.94Mo-0.05Hf-0.01Ho定向共晶合金的高温氧化行为

在900-1150℃氧化的NiAl-28Cr-5.94Mo-0.05Hf-0.01Ho定向共晶合金,在其表面生成了连续的Al_2O_3氧化膜,具有良好的抗氧化性能。定向凝固工艺使合金的组织细化并提高了Cr(Mo)相中Al元素的含量,以及加入微量稀土元素Ho,都有利于生成Al_2O_3氧化膜。在NiAl-28Cr 5.94Mo-0.05Hf-0.01Ho定向共晶合金的氧化过程中表面氧化膜发生相变θ-Al_2O_3→α-Al_2O_3,导致其1000℃氧化质量增加出现反常。     

高精度钾热管铝凝固点炉研制及性能测试

热管作为等温炉衬可提高固定点炉温场均匀性。为提高铝凝固点复现水平,研制了1套高精度钾热管铝凝固点炉。介绍了钾热管和固定点炉的研制流程,并测试了钾热管固定点炉性能。测试结果表明:采用分段升温的方式,炉子升温曲线平缓,整个升温过程中没有明显过冲现象,可有效保护铝凝固点容器的使用寿命;钾热管铝凝固点炉垂直温场均匀性为6.6mK;利用该钾热管铝凝定点炉可以实现铝凝固点温坪的复现,温坪重复性为0.02mK。     

三段控温固定点炉复现铝凝固点研究

固定点炉垂直温场均匀性是影响ITS-90国际温标固定点温坪质量的重要因素.为了提高铝凝固温坪的复现水平,设计了三段控温固定点炉,利用金属外壳铝固定点容器,研究了垂直温场均匀性及其影响因素;在此基础上,采用连续热流密度法高精度复现了铝凝固点.实验结果表明:通过调整上部、中部、下部炉温的设置,可改善固定点炉温场均匀性,铝凝...     

热处理对铸造AlSiCuMg合金硅相形貌及力学性能的影响

通过对共晶硅相立体形貌的观察和定量金相学参数的测定，发现固溶处理过程中共晶硅相形貌的变化及其对合金力学性能的影响可划分为三个阶段：固溶初期硅相的熔断和钝化，使合金的塑性得到显著的提高；固溶中期以粒化为主，同时由于合金元素的充分固溶引起时效强化，合金的力学性能达到了峰值；固溶后期，硅相的粗化符合LSW粗化模型，硅相形貌呈现棱角小面特性，合金性能降低。同时，人工时效显微组织的TEM观察发现，合金峰时效时有过剩的硅质点析出，而且随着时效时间的延长，硅质点的长大很快，加速了合金的过时效。     

Experimental Investigation of the Cr3C2–C Peritectic Fixed Point

The Cr₃C₂–C (1,826°C) peritectic point was investigated for its performance as a high-temperature fixed point. Dependence on the impurity content was observed, although it was less severe for the higher of the two equilibrium temperatures obtained with the same cell, the Cr₃C₂–C peritectic point, than for the lower, the Cr₇C₃–Cr₃C₂ eutectic point. Thermal history had an effect on the melting plateau duration, but not on the point-of-inflection temperature nor on the melting range. The melting rate had no apparent effect. The repeatability evaluated as the standard deviation of the repeated melting plateaux within a day was 20 mK for the Cr₃C₂–C peritectic point, while for the Cr₇C₃–Cr₃C₂ eutectic point, this was 210 mK. For both the Cr₃C₂–C peritectic and the Cr₇C₃–Cr₃C₂ eutectic, the freezing plateaux often showed deep supercools, which made them unsuitable for use. The observed good repeatability shows the peritectic-point performance to be comparable to the best MC-eutectic high-temperature fixed points investigated so far. The insensitivity to thermal history constitutes an important and practical advantage. The low price of chromium is a clear benefit as compared to Pt–C (1,738°C) or Ru–C (1,953°C) eutectic points, the M–C eutectic points in this temperature range.