Effect of Solid Solution Supersaturation on Precipitation of γ'''' in Rapidly Quenched Ni-Al Binary Alloys

The effect of solid solution supersaturation on the precipitation of γ' in rapidly quenched Ni-Al binary alloys containing 11.6, 14.2 and 16.5 at. Pct Al was investigated. The samples were solutioned at 1250℃, quenched in iced brine, and then analyzed by electron microscopy and XRD (X-ray diffraction) techniques. In Ni-11.6 at. Pct Al alloy, ordering and phase separation took place simultaneously, resulting in a uniform distribution of γ'. A transition from uniform to bimodal γ' phase distribution occurred in the composition range between 14.2 and 16.5 at. Pct Al. This transition was accompanied by changes in the morphology of γ' precipitates. The microstructural observations were discussed in view of both kinetics and crystallographic considerations.     

热处理对La-Fe-Si合金组织结构的影响

研究了热处理对La-Fe-Si化合物组织结构的影响。结果表明,热处理保温时间在24h以内及温度在900～1300℃之间,铸态试样在两个温度点发生相变,即900～1200℃为一个相变点,α-Fe相从铸态的非主相变为主相;1300℃为另一个相变点。在900～1100℃范围材料中α-Fe相的晶胞常数逐渐减小,当热处理温度继续增加,其α-Fe相的晶胞常数缓慢增加。     

缝纫泡沫夹芯复合材料失效强度的理论预测与试验验证

基于经典层板理论和细观力学桥联模型, 提出了缝纫泡沫夹芯复合材料失效强度的理论预测方法, 并进行了失效强度的相关试验验证。其中, 将缝纫复合材料面板看作单层组成的准层状结构, 采用经典层板理论进行逐层失效分析, 并同时考虑了局部皱曲的面板失效模式; 而对缝纫泡沫夹芯, 引入桥联模型计算其各组分材料中的应力, 并通过对各组分材料选取适当失效准则来建立失效判据; 对于缝纫泡沫夹芯复合材料采取逐级加载方式, 当面板或者夹芯失效时, 则认为其发生整体失效, 由此可以确定其在不同载荷形式下的失效强度。此外, 通过试验得到了缝纫泡沫夹芯复合材料板试件在平压、 侧压、 横向剪切及三点弯曲载荷形式下的失效模式及其失效强度, 并利用本文方法对缝纫泡沫夹芯复合材料的失效强度进行了理论预测, 所得结果与试验吻合, 证明了本文方法的有效性。      

The microstructure and mechanical properties of TaN/TiN and TaWN/TiN superlattice films

The microstructure and the microhardness of the TaN/TiN and TaWN/TiN superlattice films have been studied with X-ray diffraction, transmission electron microscopy and microhardness tester. The results showed that both TaN/TiN and TaWN/TiN superlattice films have a cubic crystal structure with an epitaxially grown mode of polycrystallinity. Lattice constants of superlattice films are between those of the constituent materials. The superhardness effect was found in TaN/TiN and TaWN/TiN superlattice films and the maximum hardness value was 40.0 GPa at a modulation period of 9.0 nm for TaN/TiN, and 50.0 GPa at a modulation period of 5.6 nm for TaWN/TiN. It is proposed that the lattice mismatch affects the microhardness value and the peak position of maximum hardness. The inhibition of dislocation motion by alternating stress fields of interfacial coherent strains is believed responsible for hardness anomalies.     

集成鱼骨分析与进化法则的产品失效预测及问题求解

 基于传统FMEA在失效问题分析与解决方面的不足,提出了一种集成鱼骨图、FMEA和进化法则的创新设计方法．利用鱼骨图层次化分析辅助FMEA全面挖掘可能发生的失效模式,按照FMEA的规范表达分析失效模式并确定风险优先指数RPN,然后运用进化法则针对失效问题进行有效的解决,提高了解决问题的效率．最后通过铁路减振的示例验证了该集成方法的可行性．     

La2O3-Y2O3-ZrO2纳米陶瓷粉末的制备及高温相稳定性

用化学共沉淀法制备4.5%Y2O3-ZrO2(YSZ)和0.6%La2O3-YSZ、0.8%La2O3-YSZ、1.2%La2O3-YSZ(0.6La、0.8La、1.2La)(摩尔分数)纳米复合陶瓷粉末,研究了四组粉末的高温相稳定性.结果表明:采用正向滴淀方法制备的0.6La粉末(粒径～50 nm)团聚严重,而用反向...     

仿生矿化法制备可降解羟基磷灰石/氧化细菌纤维素复合材料

细菌纤维素是具有天然纳米网状结构的支架材料,对其进行氧化改性后可获得可调控的降解性能。通过仿生矿化氧化改性的细菌纤维素支架,制备了可降解羟基磷灰石/氧化细菌纤维素复合骨组织工程支架材料。观察并分析了仿生矿化过程氧化细菌纤维素的降解和羟基磷灰石的形成,并通过SEM、EDS、XRD对羟基磷灰石在可降解氧化细菌纤维素支架上沉积进行了表征,矿化7天的羟基磷灰石/氧化细菌纤维素复合材料表面和内部均有磷灰石形成,测得磷灰石的钙磷比为1.75,主要为羟基磷灰石,伴有少量碳羟磷灰石。结果表明,使用仿生矿化法成功获得了一种新型可降解羟基磷灰石/氧化纤维素复合材料支架。     

Isochronal hydrogenation of textured Mg/Pd thin films

Magnesium thin films of 350 nm, capped with Pd, were deposited on glass substrates and hydrogenated in two different conditions; namely isochronal and isothermal. As-deposited films were highly textured with Mg (001) parallel to the glass substrate. Experiments have shown that under isothermal conditions starting from 333 K, Mg films can absorb hydrogen producing MgH₂ with a random texture. When the films were heated slowly starting from the room temperature, hydrogenation gives rise to a textured MgH₂, where (110) parallel to the substrate. (101) is also present in this texture as a minor component. Formation of the textured hydride in isochronal loading was discussed within the context of the lattice mismatch in a Mg to MgH₂ transformation.     

Substrate effect on electrodeposited nanocrystalline Al-Mg alloy powders

Supersaturated dendritic Al-Mg alloy powders in globular form were produced using galvanostatic electrodeposition technique on polycrystalline Cu and Mg-substrates. The deposit produced on Cu-substrate possessed face centered cubic (fcc)-Al(Mg) phase with composition of ~ 18 at.% Mg. However, when Mg-substrate was used, initially hexagonal close packed (hcp)-Mg(Al) phase with ~ 77 at.% Mg was formed over which fcc-Al(Mg) phase with ~ 36 at.% Mg was nucleated. The results of the present study indicate that substrate crystal structure and estimated substrate-deposit lattice mismatch can influence the depositing phase and its composition but not the morphology of these powders.     

Ca~(2+)和臭氧对A3碳钢表面磷化膜的影响

在低温磷化条件下, 在磷化液中加入Ca ²⁺并以臭氧作为促进剂, 在A3碳钢表面制备了磷化膜。通过SEM、
XRD、EDS、FT--IR以及腐蚀电化学测试等手段对磷化膜进行表征, 研究了Ca ²⁺和臭氧对磷化膜的结构和性能的影响。结果表明, 在磷化液中添加Ca ²⁺所得磷化膜的质量随着Ca ²⁺浓度的提高而减小, 添加Ca ²⁺可细化磷化膜的晶粒、提高磷化膜的致密度和耐蚀性能; 溶解在磷化液中的臭氧具有细化磷化膜晶粒和促进晶粒生长的作用, 能大幅提高磷化膜晶粒的形核率和磷化膜的主体形成速度。当磷化液的pH=2.70、Ca ²⁺浓度为1.8 g/L、臭氧含量为2.50 mg/L时, 磷化膜的质量为5.46 g/m², 其耐硫酸铜点滴腐蚀时间超过122 s, 在5% NaCl溶液中的腐蚀电流为0.50 μA/cm²。     

Determination of matrix and precipitate elastic constants in (γ–γ′) Ni-base model alloys, and their relevance to rafting

A complete set of high-temperature data relevant to rafting, i.e. the elastic constants of the individual γ and γ′ phases and the elevated temperature lattice mismatch between the phases, was generated for two model ternary Ni–Al–Mo single crystal alloys. The directionality of rafting was examined experimentally in the same alloys upon uniaxial loading in compression and tension along a 100 cube axis. The key material properties and corresponding directional coarsening observations are discussed in view of the various models for rafting published in the literature.     

Pilling-Bedworth ratio for oxidation of alloys

Based on the theory of Pilling-Bedworth ratio (PBR) for metals, PBR for oxidation of alloys is suggested as Three Al₂O₃ forming alloys (Ni₃Al, NiAl and NiAl₃) were used as examples to calculate PBR with this method. The results showed significant discrepancies compared with the PBR calculated with aluminium metal. Calculation with the traditional method gave the PBR value for oxidation of Al as 1.29; calculations with the modified method gave the PBR values for Ni₃Al, NiAl and NiAl₃ alloys as 1.71∼1.88, 1.64∼1.78, and 1.48∼1.57, respectively. Received: 20 August 1999 / Reviewed and accepted: 24 September 1999     

The effect of Re and Ru on γ/γ′ microstructure, γ-solid solution strengthening and creep strength in nickel-base superalloys

A new in-house designed series of Ni based superalloys with stepwise increased Re and Ru additions has been investigated, to systematically determine the influence of Re and Ru on γ/γ′-microstructure and high temperature creep properties. Improved creep resistance and thus also a higher alloy temperature capability of up to 87 K/at.% was found for additions of Re. Additions of Ru revealed a lower temperature capability improvement of up to 38 K/at.% for low Re-containing second generation alloys. However, in third and fourth generation alloys with higher Re-contents, no significant influence of Ru on creep rupture strength was observed. The creep properties are discussed with respect to the γ′-volume fraction, γ′-size and γ′-coarsening rate, as well as the γ/γ′-lattice misfit and the γ/γ′ partitioning coefficient of the different Re and Ru containing alloys. The presented data shows, that these microstructure parameters are strongly influenced by additions of Re, but only marginally by additions of Ru. A further influence on creep rupture strength is given by the solid solution hardening of the γ-matrix, which is discussed based on solid solution hardener concentrations either experimentally derived or calculated from ThermoCalc data.     

一种含铼多晶铸造高温合金的凝固行为

在多晶铸造高温合金中加入铼并观察其铸态组织,发现在(γ+γ')共晶附近有μ相和类树枝晶γ'相析出,测定合金中各种相的形成顺序和共晶反应偏析,分析了初生μ相和类树枝晶γ'相的形成机理,研究了Re在多晶铸造高温合金凝固过程中的作用和对合金凝固组织的影响.     

Analysis of buried heterointerfacial hydrogen in highly lattice-mismatched epitaxy on silicon

We realized the epitaxial growth of a Sr layer on Si(111) with an atomically abrupt heterointerface - in spite of its large lattice mismatch (12%) with Si - by introducing a monoatomic layer of H on Si. In order to identify the buried H, we carried out a combination analysis involving neutron reflectometry and resonant nuclear reaction of ¹H(¹⁵N,αγ)¹²C analysis. We found different neutron reflectivity profiles resulting from a contrast variation between the H and D atoms at the buried heterointerface. Furthermore, the depth γ-ray intensity profiles revealed that the H at the heterointerface acts as an effective buffer layer that enables it to manage the highly mismatched epitaxy on Si.     

Hierarchically three-dimensional ZrO2/Fe3O4/C nanocomposites with Janus structure for high-efficiency electromagnetic wave absorption

Hierarchically three-dimensional(3D)materials present a pivotal challenge and opportunity in achiev-ing effective microwave absorption with synergistic effects.In this work,α-Fe2O3@ZrO2 with core-shell structure were fabricated in-situ on aramid nanofibers by a solvothermal method.Following calcination,3D ZrO2/Fe3O4/C nanocomposites with Janus structure have been successfully synthesized.By control-ling the lattice match and mismatch in both processes,a core-shell structure of α-Fe2O3@ZrO2 and Janus structure of ZrO2/Fe3O4 have been well-define performed.The composite material ZrO2/Fe3O4/C-700 has a minimum reflection loss(RLmin)of-67.4 dB at a thickness of 2.0 mm.The effective absorption band-width(EAB)at a thickness of 2.4 mm is 6.0 GHz(11.0-17.0 GHz).This study provides a novel strategy for fabricating high-efficiency electromagnetic wave absorption materials with dual synergistic effects in nanosized scale.     

等通道挤压AZ80镁合金的析出行为和性能

研究了AZ80镁合金经300℃等通道挤压(ECAP)后的组织、织构与力学性能的演变规律以及第二相析出行为的影响。结果表明:ECAP显著促进了粒状连续析出,可有效节省后续热处理时间。A路径多道次挤压最终获得基面织构;Bc路径挤压后形成基面近似平行于剪切面的织构;第二相析出对ECAP织构特征的形成没有显著影响。用该工艺可获得较高的延伸率(13%-19%),但是抗拉强度过低(300 MPa),综合机械性能不理想。可通过抑制挤压前的未溶粗大粒子的析出、减少挤压道次和降低挤压温度等措施优化AZ80的析出控制。     

Fe-38Ni-13Co-4.7Nb合金中的γ'相长大及分布规律研究

研究了Ｆｅ－３８Ｎｉ－１３Ｃｏ－４．７Ｎｂ合金中γ'相长大及分布规律。结果表明,该合金的ｒ１相不稳定,易聚集长大,其平均尺寸增长遵循时间的立方根规律,在７２０℃和６５０℃的长大速率分别为０．１０ｕｍ３／ｓ和４．２６×１０－３ｎｍ３／ｓ。γ'相的大小分布符合ＬＳＥＭ规律。其长大扩散激活能为２４２．１５ｋＪ／ｍｏｌ。Ａｌ元素的缺乏是导致γ'相不稳定的原因。     

Challenges in etch: What's new?

Challenges, new and old, are outlined for etching at the 45 nm technology node and below. The over-riding challenges pertain to improving selectivity over a wider range of materials and topographies and predicting pattern density behavior to reduce cost in mask design.