Al-Cu合金时效初期的价电子结构

用固体经验电子理论(EET)对Al-Cu合金时效初期的析出相的价电子结构进行计算.计算结果表明:合金基体析出的共格GP区、θ″相,具有比基体更强的共价键络,提升了合金的整体键络强度.从价电子结构层次上解释了时效初期的GP区和θ″相对合金强化作用的内在原因.     

含Li的Al-Zn-Mg-Cu合金沉淀析出过程的定量分析

应用小角度X射线散射技术结合TEM分析定量的描述Al-Zn-Mg-Cu-Li合金时效过程中析出相尺寸分布和形貌等信息。通过分析确定合金在几种时效状态下析出相为轴比在0．2～0．4之间的扁回转椭球形。确定了析出相特征尺寸的对数正态分布和质量依回转半径的Maxwell分布。并分析分布曲线随动力强度Ks的变化特征，可以看出，析出相尺寸和质量分布曲线基本满足随动力强度增加，几何平均值增加，分布范围变宽。     

Influence of Barium Dissolution on the Electrokinetic Properties of Colloidal BaTiO3 in an Aqueous Medium

Hysteresis in the electrokinetic behavior of colloidal hydrothermal BaTiO₃ occurs during sequential acid and base titrations. Ba dissolution during acid titration results in an oxide-rich surface. When the acid-treated BaTiO₃ is titrated back to pH 10, dissolved Ba is specifically adsorbed and/or precipitated onto the particle surface. The combined effects of dissolution and subsequent adsorption–precipitation results in titration hysteresis. Most of the labile Ba can be removed by multiple acid treatments, which result in a TiO₂-like surface layer composition. Barium dissolution increases with decreasing pH but levels off below pH 4 due to diffusion through the surface oxide layer as predicted previously. A phenomenological model is offered to explain the electrokinetic behavior as a function of pH. It is suggested that inherent BaCO₃ contamination is not the primary source of dissolved Ba from hydrothermal BaTiO₃ in acidic solution.     

Fabrication of NiO Nanoparticle-Coated Lead Zirconate Titanate Powders by the Heterogeneous Precipitation Method

NiO nanoparticle-coated lead zirconate titanate (PZT) powders are successfully fabricated by the heterogeneous precipitation method using PZT, Ni(NO₃)₂·6H₂O, and NH₄HCO₃ as the starting materials. The amorphous NiCO₃·2Ni(OH)₂·2H₂O are uniformly coated on the surface of PZT particles. XRD analysis and the selected-area diffraction (SAD) pattern indicate that the amorphous coating layer is crystallized to NiO after being calcined at 400°C for 2 h. TEM images show that the NiO particles of ∼8 nm are spherical and weakly agglomerated. The thickness of the nanocrystalline NiO coating layer on the surface of PZT particle is ∼30 nm.     

坝体坝基渗水及其析出物对大坝影响分析

坝基坝体渗水对大坝安全运行有不利影响。本文采用现场检查、水样试验、析出物试验、资料分析等手段,对碾压混凝土坝运行期渗水及其析出物对大坝的影响进行了较全面的分析,并提出了运行期需关注的问题。     

Artifacts introduced by ion milling in Al-Li-Cu alloys

Ion milling is commonly used to prepare specimens for observation under transmission electron microscope (TEM). This technique sometimes introduces artifacts in specimens contributing to misleading interpretation of TEM results as observed in the present investigation of Al-Li-Cu alloys. This type of alloy, in general, contains several kinds of precipitates, namely δ′ T₁, and θ′. It is found that ion milling even for a short time produces drastic changes in the precipitate characterics as compared to standard electropolishing methods of specimen preparation for TEM. Careful analysis of selected area diffraction patterns and micrographs shows that after ion milling δ′ precipitates are very irregular, whereas other precipitates coarsen and they are surrounded by misfit dislocations. In situ hot-stage TEM experiments were performed to relate the microstructure to that observed in the ion-milled specimen. Results and causes of ion milling effects on the microstructure are discussed in relation to standard electropolishing techniques and in situ hot-stage experiment.     

Inconel718合金摩擦焊接头析出相溶解机制研究

对Inconel718高温合金惯性摩擦焊接接头焊缝的γ′、γ″及δ等相的溶解行为进行了研究，场发射扫描电镜和透射电镜观察发现，焊缝中的γ′和γ″在焊接热循环和摩擦剪应力作用下全部溶解，并呈现突变现象，即γ′和γ″量的减少呈陡降趋势；δ相部分溶解，且滞后于γ′、γ″相的溶解。     

Influence of Aging Treatment on the Mechanical and Electrical Properties of Cu-0.5%Be Alloy

The influence of aging treatment on the microstructure,mechanical properties and electrical conductivity of Cu-0.5 wt pct Be alloy for connector material applications was investigated.The properties of mechanical strength and electrical conductivity increase with increasing aging temperature and time.Microstructure of the aged Cu-Be alloy revealed that grain size and fraction of low angle and high angle grain boundary were not greatly changed;however,transmission electron microscopy （TEM） analysis exhibited that beryllides precipitation （CoBe and NiBe） with a size of 50 nm were distributed in grains.It was,therefore concluded that these beryllide precipitates improved the mechanical strength and also it was favor in improvement of electrical conductivity.     

热处理对SiCp/Al-6%Mg复合材料微观组织及腐蚀行为影响

采用无压渗透法制备了SiC_p/Al-6%Mg复合材料,并对其进行4种热处理工艺(T1, T4, T6和退火)处理,研究了热处理工艺对SiC_p/Al-6%Mg复合材料微观组织和腐蚀行为的影响。结果表明,复合材料在4种热处理工艺下均出现了界面反应产物Si、MgA1₂O₄ 和 Mg₂Si。界面反应产物析出量(f)与热处理工艺密切相关,并呈现出如下规律：f_T1< f_T4< f_T6annealing。界面反应析出物是导致复合材料发生点蚀的主要原因,从而促进复合材料发生腐蚀。热处理工艺能影响界面反应析出量而间接影响复合材料的腐蚀速度(j_corr)：j_corr-T6> j_corr-T4> j_corr-T1。