多孔体制备工艺对C/C-SiC复合材料弯曲性能的影响

以针刺整体炭毡为坯体,采用CVD和树脂浸渍／炭化混合法增密制备了4种C／C多孔体,然后熔硅浸渗C／C多孔体制备了C／C-SiC复合材料;研究了不同炭涂层、高温热处理对C／C-SiC复合材料弯曲强度和断裂方式的影响。结果表明：热解炭涂层可减少制备过程中炭纤维的损伤,具有适中的界面结合强度,使复合材料的弯曲强度达到161．5MPa,表现出良好的“假塑性”;适当选择高温热处理工艺可制备弯曲性能较高,具有一定“假塑性”的C／C-SiC复合材料。     

DD3单晶高温合金的热腐蚀行为

用涂９０Ｎａ２ＳＯ４（ｗｔ％）和１０ＮａＣｌ（ｗｔ％）的混合盐膜法研究了单晶高温合金ＤＤ３在９００℃空气中的热腐蚀行为。结果表明，ＤＤ３单晶合金的高温热腐蚀是灾难性的；其动力学曲线无明显孕育期，但有明显的阶段性。文中对各阶段的腐蚀机理进行了简要的讨论。     

Elevated temperature Mg-Al-Sr: Creep resistance,mechanical properties,and microstructure

Mg-Al-Sr-based alloys (AJ alloys) have shown superior creep performance and tensile strength at temperatures as high as 175° with stresses up to 70 MPa. Mg-6Al-2.4Sr (AJ62x) exhibits an optimum combination of creep resistance and excellent castability, while AJ62Lx (strontium <2.1) has better ductility than other AJ formulations. The AJ alloy microstructure is characterized by the Al₄Sr-α(Mg) lamellar phase that forms at the interdendritic/grain boundary region of the primary magne sium matrix. Mg-5Al-2Sr (AJ52x) contains a ternary phase that was tentatively named Al₃Mg₁₃Sr. When the strontium level is low in AJ62x, the volume fraction of Al₄Sr is reduced, the aluminum supersaturation of the magnesium primary phase increases, and Mg₁₇Al₁₂ forms. In this article, a mechanism is proposed whereby the creep resistance decreases with the strontium level but the tensile strength and ductility increase. For more information, contact Eric Baril, Noranda, Noranda Technologies Centre, 240 Hymus Pointe-Claire (Montréal), Québec, H9R 1G5 Canada; (514) 630-9347; fax (514) 630-9379; e-mail eric.baril@ntc.noranda.com.     

偶氮氯膦Ⅰ光度法同时测定硅砂中氧化钙和氧化镁

试验了Ca2 、Mg2 与偶氮氯膦Ⅰ同时显色的条件,Ca2 、Mg2 对显色的相互影响。试验结果表明,100μg CaO(50 ml)存在下,不影响MgO的显色,0～50μg MgO(50 ml)符合比耳定律,相关系数r=0.999 8,表观摩尔系数ε=1.83×104 L/mol.cm。30μg MgO(50 ml)存在下,不影响CaO的显色,0～100μg CaO(50 ml)符合比耳定律,相关系数r=0.999 1,表观摩尔系数ε=1.53×104 L/mol.cm。建立了偶氮氯膦Ⅰ光度法同时测定硅砂中CaO、MgO的方法。用所建立的方法对硅砂标准样品进行测定,结果十分满意。     

汽车半轴楔横轧机机架动态特性有限元法分析

目前,对楔横轧机机架的研究多集中在静力学分析,而动力学分析研究较少。本文应用ANSYS有限元动力学分析模块,求出了汽车半轴楔横轧机机架在现有边界条件下的固有频率和振型,并对机架的整体模态、谐响应以及机架上影响轧制精度的点在给定的激励下的位移响应进行了详细分析,结果表明该轧机在现有参数下的设计是可靠的。     

Preparation and characterization of TiO2 photoelectrode codoped with aluminum and boron and its application in dye-sensitized solar cell

Nanocrystalline titania films codoped with aluminum and boron were prepared by cathodic vacuum arc deposition. In the process, titanium alloy target was used under an O2/Ar atmosphere, and sensitization of films were carried out by natural dye-sensitized complex in anhydrous ethanol. The structure, surface morphology and UV-vis spectra of titania films codoped were measured by X-ray diffraction analysis, scanning electron microscopy and ultraviolet-visible spectrometer. Theas-deposited films are found to be amorphous. The films annealed were examinedto be of anatase structure with orientation along the (101) planes, the averagecrystal size is in the range between 41 and 45 nm. SEM results show that thereare some pores in the codoped titania films, the optical properties of the dye-sensitized films were also measured which reveals that the spectral responses of films shift to the visible region. Under simulated sunlight illumination, the overall energy conversion efficiency of dye-sensitized nanocrystalline solar cell is 0.9%.     

Experimental and numerical study of warm deep drawing of AZ31 magnesium alloy sheet

Warm forming of magnesium alloy sheet has attracted more and more attention in recent years. The formability of magnesium alloy sheet at elevated temperature depends on appropriate processes, and the fabrication of high-performance sheet. In this research, an AZ31 magnesium alloy sheet with excellent performances is fabricated by the cross-rolling and the uniform annealing treatments. The uniaxial tensile tests are conducted using a Gleeble 3500 thermal–mechanical simulator, and the mechanical properties of AZ31 magnesium alloy sheet are analyzed. Finally, some limiting drawing ratio (LDR) experiments are performed. The experiments show that the LDR can reach 2.0 at the forming temperature of 150 °C and the drawing velocity of 15 mm/s. A warm deep drawing process is also simulated by the finite element method. The influences of drawing temperature and blank holder force on the formability are numerically investigated. The simulation demonstrated that variable blank holder force technology can improve the LDR from 3.0 to 3.5, and decrease the wall thinning ratio from 15.21% to 12.35%.     

离心铸造高镍铬铸铁复合辊套的研制

详细介绍了离心铸造高镍铬铸铁复合辊套内外层金属铸造工艺参数及整个铸造生产过程。     

扩散阻挡层对Cu-Zr纳米合金膜电阻率与残余应力的影响

用磁控溅射和离子束溅射共沉积的方法分别在以单晶硅为基体的TiN,TaN,ZrN扩散阻挡层上沉积了Cu-Zr合金膜,膜在400℃氮气中退火1h.结果表明扩散阻挡层对膜的晶体取向、电阻率和残余应力有很大影响.沉积态的膜具有强的（111）取向,且峰型严重展宽;退火后峰型明显锐化,出现（200）等晶体取向;对应TiN,TaN;ZrN三种扩散阻挡层,膜的电阻率在沉积态时分别达108,327和478μΩ·cm,退火后降至正常的数个μΩ·cm;扩散阻挡层亦可明显降低膜的残余应力,无扩散阻挡层时膜的退火应力达475MPa,有ZrN扩散阻挡层后退火应力降至149MPa.     

Einfluß des totvolumens auf die Al2O3-CVD-Abscheidung

The influence of the free gas volume around the substrate on the chemical vapor deposition of Al₂O₃ layers in the AlCl₃/H₂/CO₂ system at different pressures and temperatures has been studied. Through the water gas reaction which occurs homogeneously in the gas phase, the Al₂O₃ growth rate increases with increasing free gas volume until a certain volume is reached, after which it remains constant. For this ‘critical free gas volume’ a theoretical characteristic dimension L_max is introduced. It is defined as the normal distance from a substrate surface, at which the water molecules formed from the CO₂ + H₂ in the gas phase can no longer reach the substrate surface in the time available. The dependencies of L_max on pressure, temperature and gas flow rate deduced through this theoretical consideration show agreement with the experimental results.

Zusammenfassung

Der Einfluß des die Substrate umgebenden Totvolumens auf die Al₂O₃-CVD-Abscheidung im System AlCl₃/H₂/CO₂ wurde systematisch bei verschiedenen Drücken und Temperaturen untersucht. Durch die homogen in der Gasphase ablaufende Wassergasreaktion nimmt in allen Fällen die Abscheidungs-geschwindigkeit mit vergrößerten Totvolumen zuerst zu, bleibt aber ab einer bestimmten Totvolumensgröße konstant. Für diese “kritische Totvolumensgröße” wird die theoretische Kenngröße L_max eingeführt. Diese Größe ist als Normalabstand zur Substratoberfläche definiert, bei dem das in der Gasphase aus CO₂ + H₂ gebildeten Wasser in der zur Verfügung stehenden Zeit die mit AlCl₃ belegte Oberfläche der Substrate nicht mehr erreichen kann. Die aus dieser theoretischen Überlegung abgeleiteten Voraussagen über die Abhängigkeit des L_max von Druck, Temperatur und Gasströmungsgeschwindigkeit zeigten Übereinstimmung mit den Versuchsergebnissen.