影响Ti合金热稳定性的因素

综述了合金元素、环境气氛、相变、涂层等因素对Ti合金热稳定性的影响.     

The influence of thermal annealing on residual stresses and mechanical properties of arc-evaporated TiCxN1−x (x=0, 0.15 and 0.45) thin films

We report the stress relaxation behavior of arc-evaporated TiC_xN_1−x thin films during isothermal annealing between 350 and 900°C. Films with x=0, 0.15, and 0.45, each having an initial compressive intrinsic stress σ_int=−5.4 GPa, were deposited by varying the substrate bias V_s and the gas composition. Annealing above the deposition temperature leads to a steep decrease in the magnitude of σ_int to a saturation stress value, which is a function of the annealing temperature. The corresponding apparent activation energies for stress relaxation are E_a=2.4, 2.9, and 3.1 eV, for x=0, 0.15, and 0.45, respectively. TiC_0.45N_0.55 films with a lower initial stress σ_int=−3 GPa, obtained using a high substrate bias, show a higher activation energy E_a=4.2 eV. In all the films, stress relaxation is accompanied by a decrease in defect density indicated by the decreased width of X-ray diffraction peaks and decreased strain contrast in transmission electron micrographs. Correlation of these results with film hardness and microstructure measurements indicates that the stress relaxation is a result of point-defect annihilation taking place both during short-lived metal-ion surface collision cascades during deposition, and during post-deposition annealing by thermally activated processes. The difference in E_a for the films of the same composition deposited at different V_s suggests the existence of different types of point-defect configurations and recombination mechanisms.     

气敏陶瓷研究进展

从气敏陶瓷在实际生产生活中的重要应用价值出发,介绍了气敏陶瓷的工作原理、性能及制备方法,并列举了大量典型气敏陶瓷的工作情况及其原理,最后提出了需要努力的方向.     

INFLUENCE OF RARE-EARTH ELEMENTS ON THERMAL STABILITY OF PdSi_(16.5)GLASS

The influence of rare-earth elements,La,Ce,Pr,Nd,Sm,Eu,Gd,Dy,Ho,Er and Yb onthe thermal stability of PdSi_(16.5) glass was studied systematically by means of DSC.Allrare-earth elements,especially heavy ones,increase obviously the thermal stabilityparameters,including T_θ(T_g ,T_x ,T_g),T_(rg) and ΔE etc.The crystallization temperaturesT_(p1) and T_(p2) increase linearly with the lanthanide constriction increasing,but Eu shows ananomalous influence:Pd-Si-Eu metallic glass possesses the highest thermal stability and thelowest concentration limit of glass forming among Pd-Si-R glasses.     

Properties and Performance of High-Purity Thermal Barrier Coatings

It has been found that reducing the level of impurity oxides (particularly SiO₂ and Al₂O₃) in 7YSZ, from about 0.2 wt% to below 0.1 wt% raises the sintering resistance and the phase stability of plasma-sprayed coatings. The implications for the usage of these coatings at elevated temperatures are examined. It is concluded that using relatively high-purity powder of this type is likely to confer substantial benefits in terms of the thermomechanical stability of the coatings under service conditions. This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2007.     

异型截面筋条压弯稳定性分析及数值模拟研究

对于成形带筋整体壁板,控制筋条的变形量和防止筋条失稳是此项技术的关键,本文基于对筋条弹塑性弯曲的理论分析,给出了异型截面筋条压弯时的应力应变表达式,并对筋条压弯变形稳定性进行了分析。此外,本文应用MARC有限元软件对筋条压弯过程中的失稳现象进行了数值模拟。     

大沙河水库富营养化及蓝藻水华特点分析

依据近几年来大沙河水库水质监测和水生态调查的成果资料,通过对大沙河水库水质现状,富营养化程度和蓝藻水华特点的分析评价,总结了大沙河水库蓝藻水华呈现持续爆发,偶尔消退的特点。进一步评估了水华发生风险,分析了水库污染的原因,提出了保护和治理建议。     

恰拉水库坝坡稳定分析

寒冷地区可采用苯板解决土石坝上游护坡的冻胀问题。采用两种试验仪器测定两布一膜与苯板、坝体的摩擦参数。通过两种试验参数计算边坡抗滑稳定,分析稳定计算成果。结果表明:采用土工合成材料综合测定仪时,随着膜的粗糙程度增大,粘聚力增大,摩擦角减小,且苯板产生了变形;采用非散粒体材料摩擦角测定仪时,不能得到苯板与一布一膜、两布一膜之间的稳定摩擦角,可得到苯板与光面土工膜的稳定摩擦角。试验证明:恰拉水库护坡衬砌方式较优,边坡稳定性高,安全系数大。非散粒体材料摩擦角测定仪需进一步改进。     

沉入式桶式基础防波堤抗倾覆稳定性计算

在波浪荷载作用下,沉入式桶式基础防波堤抗倾覆稳定性是其稳定性计算的一个重要部分。假设沉入较深土层的桶式基础防波堤极限状态下的稳定性主要由桶侧土压力、桶侧摩阻力、桶底土反力、桶底摩阻力维持,其工作原理与挡土墙类似。文中假定桶体绕转动中心转动,港侧为被动土压力,海侧为主动土压力,同时假定被动侧桶底土体达到极限状态。由于下桶内部有较多隔墙,假定下桶结构与桶内土体协同变形,即桶与桶内土体看作一个整体。基于上述假设,通过解析的方式,推导了桶壁土压力及摩阻力、桶底土反力及摩阻力的表达式,建立了沉入式桶式基础防波堤满足抗倾覆稳定性要求的三维计算方法。通过数值分析与离心机试验对比,验证了本文抗倾覆稳定性计算方法的可靠性。     

水电站大坝安全等级评定中边坡因素的影响剖析

基于我国水电站大坝安全定期检查的长期实践经验,分析了运行水电站边坡失稳对大坝运行安全的主要影响后果,归纳了边坡稳定状况评价的主要工作和原则,提出了边坡安全级别确定的原则。