纳米钛-锆合金制备技术的研究进展

纳米钛-锆二元合金为固溶体合金,平均晶粒度为6～7nm,晶格类型为面心立方晶格(fcc),相对于钛和锆元素的密排六方晶格(hcp)结构稳定性更高.综合评述了采用机械合金化技术制备纳米钛-锆合金在国内外所取得的主要研究成果,并展望了其发展方向.     

机械合金化制备Co-Cu纳米晶过饱和固溶体

根据Miedema半经验理论建立Co-Cu二元系机械合金化过程的热力学模型,讨论机械合金化法制备的Co-Cu(原子分数为20%)纳米晶过饱和固溶体的热力学和动力学特点。结果表明:采用机械合金化法可以获得Co-Cu纳米晶过饱和固溶体;热力学计算结果显示,Co-Cu二元系不具有形成固溶体的热力学驱动力,Co-Cu合金经机械合金化制备纳米晶过饱和固溶体的驱动力主要来源于动力学。     

过共析Ti-Cr合金的机械合金化

以钛，铬元素粉为原料，在行星式球磨机上采用φ20mm的淬火钢球，以200r/min的球磨速度和15：1的球料比，研究了Ti-20%Cr(ω(B)和Ti-30%Cr(ω(B)两种合金的机械合金化（MA）规律，研究结果表明；在球磨初期的2h内钛的（011）主衍射峰强度迅速降低，（010）第二衍射峰强度提高并成为最强峰，同时铬的衍射峰强度提高；随着球磨时间的增加，钛和铬的X射线衍射峰均发生宽化，强度下降和衍射角左移并减小；当球磨时间为30-40h时，钛逐步非晶化，但在本试验条件下铬没有发生非晶化；MA的前10h是粉末晶粒细化，晶格应变和合金化进行的最迅速的时期，经该阶段球磨后铬的晶粒尺寸可以达到20nm，进一步示磨有利于获得过饱和固溶的合金粉末；两种合金在超过100h的MA过程中均未发现在固相合成Laves相TiCr2；确定30-40h为制备纳米晶或非晶过饱固溶Ti-Cr合金粉末的合理球磨时间。     

二元互不溶体系中纳米晶过饱和固溶体机械合金化的研究进展

互不溶体系合金在机械合金化的非平衡过程中能够形成纳米晶过饱和固溶体,并显示出与其微米尺度结构合金所不同的独特性能。纳米晶过饱和固溶体不仅是互不溶体系中重要的一种亚稳态结构,也是一种重要的纳米材料体系。综述了近年来二元互不溶体系中纳米晶过饱和固溶体机械合金化的研究进展,着重介绍了纳米晶过饱和固溶体的形成机制,以及纳米晶过饱和固溶体的热稳定性、力学和物理性能。     

不同晶粒尺寸的三元Cu40Ni40Cr20合金的制备及其显微组织研究

采用电弧熔炼和机械合金化,随后在750℃,58MPa下热压制备了晶粒尺寸差别较大的Cu40Ni40Cr20合金,用X射线衍射仪、扫描电镜等分析手段对比研究了显微组织结构.结果表明:电弧熔炼制备的晶粒尺寸较大的Cu40Ni40Cr20合金为二相,组织极其不均匀;采用机械合金化,通过控制热压条件制备的纳米晶Cu40Ni40Cr20合金仍为双相,但显微组织均匀,稳定.随着球磨时间的延长,由于晶粒细化和应变的结果,衍射峰偏移并有明显的宽化产生,Cu在Cr或Cr在Cu中的固溶度明显增加,当球磨60h后,合金已由双相变成亚稳态的单相.由于机械合金化的粉末处于非平衡态,其超固溶度溶质随热压和真空退火过程的进行会慢慢脱溶分解出来,合金已由单相变为两相,两相颗粒均成倍长大,但仍然保持纳米级尺度;机械合金化、热压和退火后样品中Cu,Ni和Cr的晶格均未发生崎变;讨论了晶粒细化对合金显微组织的影响.     

机械合金化非平衡产物

机械合金化是一种非晶平衡态材料制备的新兴技术 ,利用机械合金化技术已制备出各种非平衡态材料 :如非晶、纳米晶、金属间化合物等。文中简要叙述了机械合金化非平衡过程的特点 ,着重介绍机械合金化过程中弥散强化合金、金属间化合物、非晶、纳米晶、过饱和固溶体等非平衡相的形成及其特点 ,提出该技术的开发亟待解决的关键问题     

机械合金化制备FeMB纳米晶软磁材料的研究

介绍了一类重要的高性能软磁材料FeMB纳米晶合金的研究情况,重点论述了机械合金化法制备原理、过程参数和后续处理工艺对合金软磁性能和热稳定性的影响,以及材料的应用前景.     

机械合金化的机制

机械合金化是一种制备平衡态和亚稳态材料的新兴技术。机械合金化的热力学与动力学不同于常规的固态反应，而且相转变方式与合金系统及球磨条件密切相关。着重评述了机械合金化过程中非晶态，金属间化合物，过饱和固溶体及纳米晶形成的特点及机制。     

机械合金化法制备电动汽车电机用Fe-Si-Al合金粉

利用机械合金化法制备电动汽车电机用Fe-Si-Al合金磁粉;采用X射线衍射分析和扫描电子显微镜分别表征机械合金化过程中合金粉体的相结构和形貌,采用热分析对合金粉体的稳定性进行分析。结果表明:按照(FeSi)_(75)Al_(25)的原子比进行配料合金粉体,球磨10 h生成纳米晶α-Fe(Al,Si)固溶体,为体心立方晶体结构,粒径为1~20μm;球磨15 h,颗粒不断细化,晶粒粒径可达30 nm;(FeSi)_(75)Al_(25)磁粉在机械合金化过程中形成了具有典型层状结构且表面各种元素均匀分布的合金粉末包覆薄膜,无非晶相生成。     

机械合金化的Cu-Sn纳米晶合金的热力学稳定性研究(英文)

在纳米结构的金属及合金中,随着晶粒尺寸的下降,晶界体积分数显著增加,使得晶粒长大的驱动力提高,因此纳米金属在加热时(甚至是室温下)是不稳定的。对Trelewicz/Schuh(TS)模型进行了修正,并利用修正的模型对Cu-Sn纳米晶合金的热力学稳定倾向做了计算研究。利用机械合金化的方法制备不同溶质含量的Cu-Sn纳米晶合金,在不同温度下进行退火实验。实验结果及理论计算表明,随着溶质原子的加入及在晶界的偏聚,Cu-Sn纳米晶合金的晶粒长大得到抑制,热力学稳定性提高。     

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)。