氧化铈复合磨粒的制备

用羧甲基纤维素和氧化铈混合,经聚甲基丙烯酸苏达水、分散剂、硫酸处理悬浮聚合制备了氧化铈复合磨粒,与未经处理的氧化铈磨粒进行性能比较;并分析了分散剂种类、分散剂用量和搅拌速度对粒径的影响。结果表明,复合粒子球型磨粒具有分散流动性能好的特点,适用于抛光磨具生产。     

Corrosion protection of aluminium alloy 2024-T3 in 0.05 M NaCl by cerium cinnamate

The corrosion protection of AA 2024-T3 in 0.05 M NaCl by cerium cinnamate has been studied. Polarization measurements demonstrate that cerium cinnamate is markedly effective for suppressing anodic process of the alloy corrosion during the initial 72 h of immersion. The protection mechanism during the immersion period appears to involve two stages: the deposition of cerium cinnamate, and then hydrolysis of cerium ions forming a cerium oxide/hydroxide, prevailing over the foregoing deposition. This study also elucidates the inhibition effect of cerium cinnamate on the early corrosion attack occurred from the second phase particles by X-ray photoelectron spectroscopy and electron-probe microanalysis.     

烧熔陶瓷结合剂刚玉磨具显微结构研究

本文通过电子探针微区分析(EPMA)研究了黏土-长石-硼玻璃系烧熔结合剂刚玉陶瓷磨具的显微结构,分析了磨料中的杂质特征,并对磨料与结合剂之间的反应特点进行了研究.研究表明:烧熔结合剂呈基本均匀的玻璃状态,结合剂与磨料在界面上结合紧密.棕刚玉磨料中的杂质有TiO2、ZrO2、Fe2O3、MgO、Na2O、K2O等,并以T...     

磨粒刻划单晶SiC的SPH与FEM耦合仿真分析

目的 进一步理解金刚石线锯加工硬脆晶体材料的去除特性.方法 采用SPH与FEM耦合算法,分析磨粒刻划单晶碳化硅工件过程中的材料去除动态响应,研究不同磨粒压入深度与几何形状条件对磨粒接触力、工件刻划表面形貌与应力分布的影响规律,分析磨粒恒定深度刻划与变深度刻划两种方式下磨粒刻划工件材料的动态响应.结果 磨粒接触力的各方向分量均随刻划时间发生波动,其中x与z轴方向的磨粒接触力随时间的变化趋势相近,平稳刻划时段的磨粒接触力均值拟合方程分别为fx=3.0956h2.7264,fz=11.3813h2.6214.磨粒压入深度是影响刻划过程中工件刻划截面形貌及应力分布的主要因素.相较于圆锥体磨粒,球体磨粒刻划后的工件材料截面形貌更粗糙,但工件材料的变形及损伤层深度更小.在磨粒变深度刻划方式下,随着磨粒压入深度的增加,刻划过程中的工件材料发生了脆塑转变.结论 在保证材料去除率的条件下,需降低磨粒压入深度,以降低磨粒接触力,获得更平整的工件表面刻划形貌与更低的等效应力.     

Reduction of segregation during casting of 100Cr6 bearing steel by cerium inoculation

In order to reduce the segregation of alloying elements during casting of 100Cr6 high carbon chromium bearing steel, cerium was added to form dispersoids that act as inoculants to facilitate the formation not of columnar but of equiaxed grains. The influence of adding cerium alone to 100Cr6 steel on the degree of segregation and the resulting as-cast microstructure have been investigated. By adding cerium, the equiaxed grains became finer and the segregation diminished considerably. As a result, the rolling contact fatigue life of the steel was improved markedly. Among dispersoids, CeO₂ is supposed to play a more important role in refining as-cast structures because the observed number of CeO₂ was much larger than that of CeS and the size of the former was quite similar to that reported to be effective as inoculants. Consequently, the addition of cerium is proposed as the solution to one of the biggest subjects with regard to 100Cr6 steel, the reduction of segregation during casting.     

普通磨料深加工后处理技术的发展概况及应用领域拓展

普通磨料冶炼技术日臻成熟，依靠冶炼技术发展磨料新品种潜力日渐缩小，而在磨料加工制粒阶段采用一定的方法技术对磨料进行深加工改性处理，可以大幅提高其使用性能，本文阐述了普通磨料后处理技术的定义，类型及实际应用效果。     

Effects of acetic acid on microstructure and electrochemical properties of nano cerium oxide films coated on AA7020-T6 aluminum alloy

Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), crack-flee films with well-developed grains were obtained and grain sizes of the films decreased. Elimination of cracks and decreasing grain size of the nano cerium oxide films caused corrosion resistance to increase.     

Wear characteristics of Fe-based diamond composites with cerium oxide (CeO2) reinforcements

To obtain better wear resistance for the metal bond diamond grinding tools, cerium oxide (CeO₂) with different contents were introduced into Fe-based diamond composites. A pin-on-disc wear test was performed to assess the wear properties of the fabricated specimens, and the morphological properties of the worn surface and corresponding wear debris were evaluated to examine the wear mechanism. Results show that the Fe-based diamond composites with CeO₂ addition exhibited an improvement in the densification, mechanical properties and wear resistance. The original long rod-shaped CeO₂ particles converted into the spherical particles <1 μm, dispersing in the Sn phase. The cerium oxide acted as a sintering aid, promoting the diffusion of Fe in the Sn phase during the sintering process. The dominant wear mechanism of the specimen with CeO₂ addition was the adhesive wear, compared with the abrasive wear in the specimen without CeO₂. With the increase in CeO₂ addition amount, the wear rate decreased. But an excessive amount of CeO₂ was detrimental to mechanical and wear performances. The optimal amount of cerium oxide to achieve the best wear resistance was investigated to be 0.8 wt%.     

Spiral-structured fixed-abrasive pads for glass finishing

Loose-abrasive machining with cerium oxide (ceria) slurry is traditionally employed for finishing glass. However, the use of slurries can have a detrimental impact on the environment. Fixed-abrasive machining has received attention as an alternative technology; however, conventional fixed-abrasive tools are inefficient. In this study, spiral-structured pads with fixed-abrasive layers and abrasive holding layers are introduced to increase the quality and efficiency of fixed-abrasive tools. The finishing experiments revealed a much higher finishing efficiency and good surface quality compared to those obtained in conventional polishing with ceria slurry.     

Ce对Ni—Cr—Cu合金抗氧化性的影响

作者研究了添加0.1％和0.8％Ce的Ni—Cr—Cu合金在空气中1200℃100小时等温氧化和500小时循环氧化。Ni—Cr—Cu合金中添加微量Ce后,显著降低了氧化速率,增加了氧化膜的剥落抗力。氧化速率降低是添加Ce后各种效应综合作用的结果。它们是:(1)由于Cr的扩散加快,富Cr保护膜更迅速形成;(2)聚集在膜/合金界面附近的含Ce氧化物与空位复合,减少了膜/合金界面的空洞;(3)固溶于氧化膜中的含Ce氧化物阻碍了Cr~(3+)沿氧化物晶界的短程扩散。 提高耐剥落抗力主要原因是:(1)添加Ce使氧化膜晶粒变细,从而改善了塑性变形和适应热应力的能力;(2)0.8Ce合金中稀土氧化物“钉扎”(Keying)作用改善了膜与合金粘附性,并改变了热应力的分布状态。     

Effects of grain refinement on mechanical properties and microstructures of AZ31 alloy

Cerium was added in AZ31 alloy with the contents of 0.4%,0.8%and 1.2%respectively to produce experimental alloys. The grain refinement of Ce in the as-cast and rolled AZ31 alloy were studied by using Polyvar-MET optical microscope with a VSM2000 quantitative analysis system,KYKY2000 SEM and Tecnai G~2 20 TEM.And the mechanical properties of AZ31+Ce alloy were tested on a CSS-44100 testing system with computerized data acquisition.The results show that the cerium has a good grain refinement effect on the ...     

A study of internal face finishing of the cooling channel in injection mold with free abrasive grains

This paper deals with a finishing method for the internal face of a cooling channel located in an injection mold that makes use of free abrasive grains. The injection mold is fabricated by layered manufacturing equipment using a ferrous based metal powder. When the internal pressure is loaded to the hydraulic cylinder, the solution containing the free abrasive grains is passed through the cooling channel. The internal face is then finished by the free abrasive grains. The effects of various conditions on finishing characteristics are investigated experimentally. The results showed that the internal face roughness of the cooling channel improved significantly during the first 1000s of finishing. The significant improvement achieved during the initial stages of finishing is due to the removal of the aforementioned unstable powders. Free abrasive grains are employed to remove the unstable powder on the internal face rather than to polish the alloyed face. The high-speed flow of the free abrasive grains results in an increase in their kinetic energy, thereby increasing the force with which they collide with the internal face and resulting in an improvement of the surface roughness. The internal face finishing was effective for the improvement of the thermophysical properties in the cooling channel.     

Abrasive Polishing Assisted Nickel Electroforming Process

This paper presents a hybrid process combining electroforming technique and abrasive polishing. In a specifically developed equipment the spherical ceramic particles between the cathode mandrel and the anode are forced to continuously polish the deposition surface during nickel electrodepositing. The abrasive polishing can effectively remove the pinholes and nodules, and positively affect the crystal nucleation and therefore refine the grains and speed up the deposition process. Smooth deposition surface of Ra 0.012 μm, compact nickel deposits with the grain size of less than 80nm and the significantly improved mechanical properties have been experimentally obtained.     

Ti、Mo、W、Cr及其合金镀层与超硬磨料之间结合性能的研究

本文在研究金属与超硬磨料之间作用的基础上，讨论了实现镀层与磨料形成强力结合的条件，为高性能超硬工具的制造提供了理论和实践依据。     

The growth and structure of thin oxide films on ceria-sol-coated nickel

The influence of 14-nm thick ceria ceramic coatings deposited by the sol-gel technique on the early-stage oxidation of polycrystalline nickel at 973 K was studied by analytical electron microscopy, Auger electron spectroscopy, Rutherford backscattering spectrometry and X-ray diffraction. The size of the ceria particles in the coating was modified prior to oxidation by vacuum annealing. It was found that ceria particle size is a crucial factor affecting the oxidation kinetics, oxide microstructure, and distribution of cerium within the oxide film. Coarse ceria particles applied to the nickel surface were ineffective in the inhibition of oxidation and were spread throughout the whole oxide. Coatings with small ceria particles markedly improved the oxidation resistance. After oxidation such particles were present in the surface region of nickel oxide, acting as the sources of cerium ions segregated at the nickeloxide grain boundaries. The stereological analysis of oxide microstructure as well as microchemical examination supported the predominant role of grain-boundary segregation of cerium ions decreasing the oxidation rate. The results are discussed in terms of reactive-element effect on the development of microstructure of nickel oxide film during initial stages of oxidation.     

Protective ability of cerium-containing conversion films on aluminium

The options for electroless deposition of conversion films of lanthanum group metal oxides, in particular cerium, as an alternative to chromate conversion films (containing Cr⁶⁺) have been studied on aluminium. The main task of the study was to establish the influence of copper ions as a component of electrolytes for conversion treatment on the processes of formation and on the corrosion protective ability of cerium oxide films.

It has been ascertained that the electrochemical activation of the aluminium surface in the presence of Cu²⁺ in the electrolyte, leads to formation of oxide layers richer in cerium and possessing a better protective ability.

The presence of active cathodic sections of electroless, contact-deposited Cu has been shown to promote the corrosion activity of the system, due to the possibility of the appearance of micro-galvanic couples Al/Cu. A model experiment has been carried out to establish the inclination of the system to pitting corrosion. It has been shown that at the studied concentration of Cu²⁺ in the electrolyte the character of the corrosion does not change observably but there is a catalysing effect of the copper ions in the working electrolyte. The copper islands on the Al surface also have a catalysing effect, which is dominating in the processes of cerium oxide film formation. The chemical state and the composition of the conversion films have been defined by XPS measurements.     

AN INVESTIGATION OF BEHAVIOUR OF CERIUM IN MOLTEN IRON AND ITS REACTION ON REFRACTORIES BY MEANS OF TRACER

用放射性测量及自射线照相的方法研究了稀土元素在工业纯铁液中的去向及其与多种耐火材料的作用。实验证明: 在炼钢温度下,金属中的铈及渣中氧化铈的挥发均甚微。 在炼钢温度下钢液中的铈与粘土砖、高铝砖、镁砖、铝镁砖、硅砖、刚玉,电熔氧化镁、氧化锆等多种耐火材料均有不同程度的作用。稀土元素与不同耐火材料作用的机理不仅决定于耐火材料的化学性质,而且也取决于其物理性质。 用自射线照相方法发现,稀土与耐火材料作用产物会剥落而进入钢液形成稀土夹杂物。稀土与耐火材料作用产物及钢中稀土夹杂物在上浮过程中有相当一部分并未上浮至液面而是粘附于坩埚壁上。 对稀土钢浇铸时盛钢桶水口结瘤、汤道堵塞以及稀土加入钢液后的去向等问题进行了初步分析。     

造孔剂对金属结合剂金刚石磨具力学性能的影响

磨具中具有适量的孔隙可在磨削过程中起到排屑、冷却和促使磨具自锐的作用。由于金属结合剂磨具的烧结密度高,对金刚石的把持力较高,所以在磨削过程中磨具的自锐性较差。本文利用真空热压烧结法,在相同的试验工艺条件下,通过添加不同含量的造孔剂NaCl、K3PO4和CO（NH2）2,详细对比和分析了造孔剂种类与用量对金属结合剂抗折强度与硬度的影响。通过实验发现：造孔剂的粉末形状、造孔剂与金属结合剂的密度差都对结合剂的力学性能有直接的影响。造孔剂原料形状越规则,试样中孔的形状就越规则,对试样强度和硬度下降的影响越小;造孔剂含量越多,因孔含量随之增加,强度与硬度都会下降;NaCl较好的颗粒形状对称性以及在热压过程中不易变形的特性保证了试样中较好的孔形和对称性,它对结合剂力学性能影响明显优于造孔剂K3PO4和CO（NH2）2。     

CeO_2对NiCrBSi激光熔敷层组织和性能的影响

ＣｅＯ２对ＮｉＣｒＢＳｉ激光熔敷层组织和性能的影响田保红吴磊郑世安（洛阳工学院）杨院生（中科院金属研究所）在金属材料表面进行激光熔敷以获得特殊表面性能的研究已取得很大进展，并已用于生产，其中以镍基自熔合金应用最广［１～４］。但目前仍存在敷层与基体结合...     

磨料粒径及形状对磨料水射流切割钛合金表面微观形貌的影响

采用不同粒径与形状的磨料颗粒,在磨料水射流切割平台上切割钛合金,用超景深显微镜等设备分析,以研究不同的磨料粒径及形状对钛合金表面微观形貌的影响。研究表明:磨料粒径越大,钛合金表面所形成的划痕越长,80目磨料颗粒形成的微划痕长度约为160目磨料的5倍。且球形磨料颗粒所形成的划痕末端堆积较少,其表面线粗糙度低于9.5 μm;具有棱边的磨料颗粒所形成的划痕有唇状或鳞片状金属堆积,其表面线粗糙度在9.5～13.0 μm间;柱体形的磨料颗粒冲击形成的划痕带有尖锐的棱角,其表面粗糙度大于13.0 μm。