2Cr13钢渗硼层的组织结构与耐磨性

本文研究了2Cr13不锈钢渗硼层的组织和耐磨性。研究发现,渗硼层由硼化物层和过渡区构成,而硼化物层又由极薄的(Fe,Cr)B层和相当厚的(Fe,Cr)_2B层组成,在硼化物上分布有少量的(Fe,Cr)_3(C,B)。过渡区是在细小弥散的两相基体上分布着块状和网状碳化物。渗硼试样的耐磨性比常规处理试样高出4—5倍。     

固体粉末法硼铬共渗研究初步

本文初步研究了固体粉末法硼铬共渗技术,并得出:用固体粉末法可实现硼铬共渗;共渗层中除有硼化铁Fe_2B或(Fe,Cr)_2B)以及固溶体外,碳化铬(Cr,Fe)_7C_3也可以成相;并得到了两层化合物组成的结构,其中(Cr,Fe)_7C_3为连续层.     

烧结钢固体渗硼的一些探讨

普通烧结钢通过固体渗硼处理,可获得高硬度、耐磨性好、硼化物致密程度高的渗硼层,渗层与基体结合紧密、硼化后产生的尺寸变化与烧结钢的密度关系特别小,零件的外观改变也很小。本文通过对Fe—Cu—C系不同密度的烧结钢与相当合碳量的65碳钢进行固体渗硼对比,得出温度和时间对烧结钢固体渗硼与一般金属材料固体渗硼具有相同规律,而且在同一工艺条件下,烧结钢固体渗硼的渗层厚度、致密度及与基体的咬合性,均优于一般金属材料     

热处理对镍基合金涂层与基体结合界面的影响

通过热浸镀法在普碳钢表面成功制备镍基合金涂层.为了提高镍基合金涂层与钢基体之间的结合强度,对镀有镍基合金涂层的基体进行了热处理.研究了热处理前、后结合界面处的显微组织和力学性能.结果表明,与热处理前相比,热处理后界面附近的涂层中析出物长大,界面处存在不连续块状铁的硼化物,界面两侧镍、铁互扩散距离增加,靠近界面的过渡带由5～8μm变为20μm.热处理前、后涂层均由γ-(Fe,Ni)、CrB、Cr2B和Cr3C2等相组成,过渡带相组成为γ-(Fe,Ni)、微量CrB和Fe23(C,B)6.热处理后,显微硬度由界面向涂层内逐渐增加,界面结合强度由140MPa提高到200MPa.     

20Cr钢渗硼后感应加热复合处理

20Cr钢固体渗硼后,再经高频感应加热10s,20s,30s,40s,研究了经过不同时间加热后渗硼层深度的变化及物相变化。试验结果表明,随感应加热时间的增加,硼化物层深深度增加,渗层中的FeB相逐渐变成Fe2B相,加热时间达到30s时已几乎全部变为Fe2B。     

模具钢的渗硼工艺和组织与多冲压缩性能

本文从多冲压缩抗力角度讨论了模具钢渗硼工艺和金相组织。结果指出:模具钢渗硼层在多次冲击压缩载荷下发生一定的塑性变形。渗硼组织中单相硼化物Fe_2B具有较好的塑性和较高的多冲抗力,提出获得渗硼层中单相硼化物Fe_2B的热处理工艺。     

硼碳共渗剂中木炭作用的研究

本文研究了以渗硼为基的固体硼碳共渗处理。结果证明,木炭对渗硼有一定的催化作用。当共渗剂中的木炭和硼铁含量控制适当时,可获得性能较好的Fe_2B单相渗层;而且渗层增厚,过渡区增加,使硬度梯度减缓,硼化物层的脆性降低。此外,共渗剂的生产成本下降,提高了经济效益。     

固体渗硼及过渡层碳含量控制途径的初步探讨

为了解决钢渗硼时出现富碳过渡层这一问题,本文在分析对比几种渗硼方法的基础上,提出应用硼砂、硅和碳酸钠为渗硼剂,使钢件在渗硼过程中适当脱碳,以控制硼化物层内侧碳元素含量的无毒固体渗硼的方法。文中对渗硼剂的选择,渗硼机理,渗硼组织特征,影响渗硼质量因素等作了初步的探讨。本文通过热力学分析指出,这一渗硼方法是可行的。试验表明,45钢经950℃渗硼后可以获得预期的过渡层组织,过渡层不增碳。这一渗硼方法,由于渗硼剂具有对基体材料脱碳——渗硼的特性,可以控制碳钢硼化物层内侧组织,对高碳钢或某些高合金钢渗硼也能获得梳齿状硼化物层,对提高工业纯铁软磁性元件的表面耐磨性能也取得良好的使用效果,而且成本低,不污染环境,因此,可以预期它对发展渗硼工艺的应用,将会有积极的作用。     

单相渗硼层的形成及硼化层中的相变

单相渗硼层的性能,大大优于双相渗硼层,有关单相渗硼层的获得,我们已作过报导,本文主要是采用双相渗硼层的试样,经高温真空退火后(900℃,10~(-2)mmgH),使用X射线衍射分析,扫描电镜,电子探针等手段,研究渗硼层的形成及相的转变,得到如下的结果: (1)具有双相渗层的45~#钢和Gcr15钢试样,经900℃,10~(-2)mmHg4小时退火后,FeB区均减少,总的渗层有所增加。 (2)硼化物层中出现的一些黑色点块状,大部分是夹杂,有些是空洞。 (3)渗硼层的形成,除了在[5]中所指出的是一种成核成长过程外。我们还观察到单个硼化物针的精细结构,如照片5所示,结合X射线衍射分析,进一步提出了我们对硼化物层形成机理的看法。     

用多元回归分析方法测定碳钢单相渗硼层厚度的数学公式

本文通过对大量所测数据进行数理统计，利用多元回归分析和相关分析的方法，得出了碳钢单相渗硼层（Fe2B0厚度与加热温度、保温时间、含碳量之间关系的数学公式。试验结果表明该数学公式准确可靠，如果工艺参数已知，就可通过公式计算预测得到渗硼层厚度。》     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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