长周期有序堆垛相对Mg-Gd-Y-Zn-Zr合金腐蚀行为的影响

研究不同长周期有序堆垛(LPSO)相含量对Mg-Gd-Y-Zn-Zr合金腐蚀行为的影响,对于新型高强耐蚀镁合金的设计具有重要的指导意义.为此,通过金相观察、SEM形貌及能谱分析、电化学测试及浸泡试验等手段考察了Mg-Gd-Y-Zn-Zr合金在5％NaCl溶液中的电化学及腐蚀行为,以确定不同LPSO相含量对镁合金抗蚀性能的影响.结果 表明:Zn元素对Mg-Gd-Y-Zn-Zr合金中LPSO相的形成和分布起决定性的作用,当合金中不合Zn元素时,不会形成LPSO相;随着Zn元素的增多,LPSO相的体积分数不断增加,形态从薄片层状向块状转变.腐蚀过程中首先在合金基体表面形成一层均匀连续的腐蚀产物层,随Zn含量增加合金表面腐蚀产物层的厚度降低,合金腐蚀形态从全面腐蚀向局部腐蚀转变;LPSO相在局部腐蚀过程中充当腐蚀微电池的阴极,加速合金基体的腐蚀溶解.     

新型Cu-Cr-Ni系耐海水腐蚀钢耐蚀性能及机理EI北大核心

针对海洋环境腐蚀特点,通过添加合金元素Cu,Cr和Ni开发一种新型船体用耐蚀钢(B-NS)。利用电化学实验、全浸实验和周浸实验对B-NS的耐蚀性能进行评估,同时通过扫描电镜和能谱对锈层截面形貌和成分进行分析。结果表明:合金元素的添加可有效降低B-NS钢的饱和电流密度和全浸以及周浸条件下的腐蚀速率,同时促进周浸条件下更加稳定、致密保护性锈层的生成。合金元素赋予B-NS钢优异耐腐蚀性能,主要表现在提高B-NS钢热力学稳定性,促进锈层生成以阻挡侵蚀性介质腐蚀基底和赋予锈层阳离子选择性,阻止Cl-渗透进锈层。     

低成本Al-Ti-Cr高强耐海水腐蚀钢耐蚀性能研究

本工作以普碳钢为基体,添加Cr、Ti、Al等元素制备了新型低成本高强耐蚀钢,通过动电位极化、交流阻抗、周浸腐蚀实验和盐雾加速腐蚀实验研究了低成本Al-Ti-Cr高强耐蚀钢的耐海水腐蚀性能.结果表明:钢中的Cr能促进锈层向致密的α-FeOOH进行转变;Al和Ti提供阳极保护的同时,Al还能产生致密的Al2O3分散在锈层表面延缓腐蚀介质向基体的侵蚀,而Ti能够呈点状或者片状富集在锈层内部,对晶间腐蚀起到一定的保护作用,大幅度提高了耐蚀钢的耐蚀性能.     

低合金钢的大气腐蚀规律研究

大气腐蚀受自然环境影响因素很多.通过暴露试验,对09CuPTiRE等8种低合金钢和普通碳钢(A3钢)在宜昌、三斗坪、秭归3个试验点进行了大气腐蚀试验,获得了1,2,5 a的腐蚀数据.采用扫描电镜、X射线衍射仪和电子探针分别进行了锈层形貌观察、结构分析及锈层内合金元素分布的测试,采用电化学腐蚀测试仪对锈层进行了阳极极化曲线测定.结果表明:试样在宜昌站的平均腐蚀速率(16.9～23.9 μm/a)是三斗坪站(9.4～14.6 μm/a)的1.5倍左右;耐蚀性最好是09CuPTiRE钢,暴露5 a后其相对耐蚀性在三斗坪约为A3钢的1.54倍,在宜昌约为A3钢的1.41倍.锈层的物理分析及阳极极化曲线的测定验证了暴露试验结果.     

外加电位对X80钢在玉门土壤模拟溶液中应力腐蚀的影响

采用慢应变速率拉伸实验研究X80钢在土壤模拟溶液中的应力腐蚀敏感性。以玉门地区的碱性土壤为基础,分析不同电位对应力腐蚀的影响。用扫描电镜对断口及二次裂纹形貌进行观察。结果表明:阳极电位下X80钢应力腐蚀敏感性不高。高阳极电位下,阳极溶解在一定程度上抑制了应力腐蚀。阳极电位较弱以及开路电位下,阳极溶解较弱,裂尖和其他表面存在溶解性差异,这些因素有利于裂纹扩展。但是较慢的溶解速率以及相对高的应变速率使得裂纹没有足够时间发生有效扩展,应力腐蚀敏感性仍然较低。当外加阴极电位时,裂尖发生阳极溶解而其他位置受到阴极反应抑制,应力腐蚀敏感性增加。随着阴极电位降低,不断增加的氢影响裂纹萌生和扩展,应力腐蚀敏感性随外加电位的降低而增大。     

微合金元素复合调控对Q345qE桥梁钢耐蚀性能的影响

为了研究微合金元素复合调控对Q345qE桥梁钢耐蚀性能的影响，利用共聚焦激光扫描显微镜(CLSM)、电化学工作站、场发射扫描电镜(FE-SEM)、X射线衍射(XRD)仪研究了合金元素Cr、Ni和Cu复合调控对Q345qE桥梁钢的耐蚀性能的影响规律。结果表明：Cr、Ni和Cu微合金元素复合调控提升了锈层的致密性和保护性。Q345qE桥梁钢表面锈层中的Cr元素可在内锈层中富集，有效阻挡了Cl^-等侵蚀性离子的渗透和传递，增强了锈层对基体的保护能力。合金元素调控后，Q345qENH钢锈层中比γ-FeOOH更稳定的α-FeOOH所占比例增大。经过微合金元素复合调控的Q345qE桥梁钢相比于普通Q345qE在3.5%NaCl溶液中具有更好的耐蚀性。     

Si对碳钢耐大气腐蚀性能的影响

通过周浸加速腐蚀试验,采用SEM观察腐蚀试样表面和截面形貌,X射线能潽(EDAX)对锈层截面进行分析,X射线衍射(XRD)测定腐蚀产物的物相组成,在利用废钢中残Cu、P的基础上,研究Si对碳钢耐大气腐蚀性能的影响.结果表明,Cu、P能明显提高钢的耐腐蚀性能,而在模拟工业大气条件下Si的加入一定程度上减弱了钢的耐蚀性.     

不锈钢在熔融NaCl中的电化学-化学-稀释模型

为分析不锈钢在熔融NaCl中的腐蚀机制,通过850℃熔融NaCl完全浸没实验,测量了168 h内3种不锈钢的腐蚀动力学曲线,借助SEM、EPMA、EDS等设备表征了试样横截面形貌、元素分布等特征,研究了Ti元素对合金耐蚀性影响机制,采用X射线衍射仪检测了腐蚀24h后熔融盐成分和168 h后试样表面成分,建立了电化学-化学-稀释联合作用腐蚀模型.结果表明:在熔融NaCl腐蚀介质中,金属材料作为阳极被溶解,吸附氧得到电子变成O2-作为阴极;金属阳离子与O2-在熔融NaCl中发生化学反应,生成易挥发性氯化物逃逸系统;熔融盐作为传质媒介,稀释腐蚀层区域的腐蚀产物浓度,提高腐蚀速度.合金中电极电位最负的微量组元优先溶解后形成微小孔隙,增大了微阳极表面积,加速腐蚀反应过程.     

AZ31镁合金在含NaCl和Na2SO4薄层液膜下的腐蚀行为

为研究大气污染物对镁合金腐蚀的影响规律,采用室内模拟暴露实验,分析AZ31镁合金含有NaCl和Na2SO4的薄层液膜下的电化学腐蚀行为.结果表明:AZ31镁合金表面沉积NaCl和Na2SO4薄液层中的腐蚀动力学符合幂函数规律,说明NaCl和Na2SO4对AZ31镁合金腐蚀有加速作用;AZ31镁合金在NaCl薄层液膜下,阳极极化电流密度增大,R f和R ct值降低,促进了阴极去极化历程,增强了阳极活性溶解,加剧镁合金的阳极溶解;而在Na2SO4薄层液膜下,R f和R ct值增大,击穿电位与腐蚀电位的差值(ΔE)减小,这是由于难溶的硫酸盐和Mg(OH)2覆盖在AZ31镁合金表面,使金属溶解和离子扩散速率降低,导致阳极过程阻滞.     

经济型耐大气腐蚀钢大气曝晒腐蚀性能研究

随着耐大气腐蚀钢的应用越来越广泛,掌握其耐大气腐蚀性能显得十分重要.采用电化学方法、电子探针等手段对JT345经济型耐大气腐蚀钢在北京、青岛、沈阳3地1年大气曝晒的试样进行分析研究,并采用Q235B和Corten A钢作为对比钢.电化学试验表明,大气腐蚀过程中生成的锈层,使电化学阳极过程受到显著的阻滞.电子探针与电子能谱分析结果表明,JT345钢的内锈层存在有效合金元素的富集,使内锈层结实、致密、牢固,抑制了腐蚀性物质的侵入,保护了基体金属.结果表明JT345经济型耐候钢具有优良的耐蚀性能,腐蚀率接近CortenA的水平,随着曝晒时间的延长,腐蚀率还将显著地下降,JT345钢的耐大气腐蚀的优越性将会更加充分体现出来.     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。