Effects of Rare Earth on Behavior of Precipitation and Properties in Microalloyed Steels

The influence of rare earths on the behavior of precipitation of 14MnNb,X60 and 10Mn V steels was studied by STEM, XRD, ICP and thermal simulation method. The main carbonitride precipitates are Nb(C, N), (Nb, Ti) (C, N) and V(C, N). In austenite RE delays the beginning of precipitation, and decreases the rate of precipitation. In ferrite RE promotes precipitation and increases the amount of equilibrium carbonitride precipitation. RE can make precipitates fine,globular and dispersed in the microalloyed steels. With the increase of the amount of RE in steel, the amount of precipitation increases. The promotion effect is weakened with excessive RE. RE has only little influence on the strength of microalloyed steel, but it can improve impact toughness effectively.     

Role of Rare Earth in Low Sulphur Nb-Ti-Bearing Steel

The effect of rare earth on the microstructures, mechanical properties and inclusions in low sulphur Nb-Ti-bearing steel were investigated. It is shown that the transverse yield point, the traverse tensile strength and elongation of testing steels decrease initially and then rise with increasing content of rare earth. The impact energy values of the testing steels exhibit a contrary trend. Proper amount of rare earth in the steels can improve the anisotropy of impact toughness above -20℃ and it does not affect the type of microstructures which are still composed of ferrites and pearlites, but the pearlite amount increases. On one hand, rare earth cleans the molten steel and reduces the amount of inclusions; on the other hand, rare earth makes the inclusions spheroidizd, refined and dispersed, and thus improves the distribution of inclusions.     

夹杂物对稀土金属丝塑性和韧性的影响

稀土金属中的酸不溶物是影响其塑性、韧性的重要原因,将所述酸不溶物含量限于一定水平,则能保证稀土金属合格的塑性和韧性.     

稀土镁硅铁合金中的氧化镁夹杂物

本文论述了稀土镁硅铁合金中主要非金属夹杂物—氧化镁的生成原因及其对应用的危害 ,提出了降低合金中氧化镁的方法。     

Study on Y-Base Rare Earth Alloy in Ultra-High Hardfacing

The effect of Y-base rare earth alloy in ultra-high hardfacing was observed by means of OM, SEM and XRD. Precipitated carbide can be metamorphosed and spheroidized in surfacing by adding Y-base rare earth alloy, which contributes to the increase of precipitated carbide. Rare earth combined with oxygen and sulfur can improve the morphology of slag inclusion as well as purify surfacing. The result shows proper rare earth alloy in surfacing can fine its microstmcture, improve hardness and impact toughness.     

稀土萃取动力学研究进展

本文讨论了稀土萃取动力学的理论、研究方法和稀土研究体系的进展。     

Progress of Study on Application of Rare Earth Metals in Steels

With the improvement of the clean steel by degrees, the functions of rare earth metals in steel are more focused on modification of inclusions and micro alloying.The new study concerning the application of RE metals in clean steels were investigated by ICP, metallographic examination, SEM, EDS, EPMA, TEM and IMMA.The mechanism of corrosion resistance in the weather resistance steel was clarified.The mechanism of abrasion resistance and the life of fatigue enhanced in the RE - heavy rails steel were discussed.Progress in study of application of rare earth metals in steels (including weather resistance steel, low alloy steel, and heavy rails steel) was covered in this paper.     

Thermodynamics of Modifying Effect of Rare Earth Oxide on Inclusions in Hardfacing Metal of Medium—High Carbon Steel

The modifying effect of rare earth(RE)oxide on inclusions in hardfacing metals of medium-high carbon steel was investigated by means of thermodynamics,The thermodynamic analsys for inclusion formation shows that RE oxide can be reduced to RE element by carbon,then the RE element can react with oxygen and sulfur to form the RE oxide,RE sulfide and RE oxide-sulfide in hardfacing molten pool.The deoxidization and the desulphurization can be carried otu and the liquid metal can be purified.In addition,RE oxide can also react with sulfur to form RE oxide-sulfide dirdctly.Therefore,the harmful effect of sulfur can be decreased.     

稀土在铍铜合金中的应用

通过本文的工艺研究及试验，使稀土成功地应用于铍铜合金中，铸锭由于其工艺特点而常出现的气孔，夹杂等缺陷得到了控制，同时大大提高了合金的综合性能，稀土对合金的作用与加入量有直接关系。过多与不及都不好，Cu-RE中间合金在铍铜合金中的最佳加入量为0.1%-0.12%。     

Comparative Crystal Chemistry of Rare Earth Minerals

Polyhedral analysis is used to study the geometrical limits of the crystal structure on isomorphic substitutionof rare earths.The rare earth sites in the structure may be distinguished into six groups on the basis of meanionic radii of the substituting cations in each rare earth site:Y,Y+Ca,REE,REE+Ca,Ce+Ca,Ce.The calcula-tion of volumes of 70 rare earth polyhedra indicates that the polyhedral volumes of the heavy rare earth are in arange of 13×10~(-3)～28×10~(-3) nm~3,the volumes of light rare earth polyhedra are in 20×10~(-3)～40×10~(-3) nm~3,and the polyhedral sizes suitable to isomorphic substitution of all REE are about 21×10~(-3)～29×10~(-3) nm~3.Thesize of REE polyhedra depends on mean ionic radii in REE sites,coordination number and linkage of polyhedra.In structures where exist two kinds of polyhedra,with the change of composition in REE site,both REEpolyhedron and anion group polyhedron tend to be more distorted,leading to the change of structural symmetry.The contrary distortion tendencies of both polyhedra favours the stability of the structure.The phenomena maybe interpreted by the potential energy distribution or the potential energy compensating mechanism of thecrystal.     

稀土元素在钯基氢净化材料上的应用

根据近年来钯基氢净化材料的研究状况,综述了添加稀土元素对钯基氢净化材料的影响。重点从稀土元素对钯吸氢后形成α相向β相的转变、透氢性能、力学性能以及有害杂质污染的抵抗能力等4个方面进行了阐述。说明添加稀土元素,特别是Y可明显改善钯膜的性能,为低廉、高效获得高纯氢提供了良好的途径。     

Development of Rare Earth Hydrometallurgy Technology in China

A whole industral system for mining, dressing,smelting, separation of RE has been established inChina. The RE industrialization level and productquality have been developed speedily. The yield of REproducts in China makes up more than 9…     

Preparation and Corrosion Resistance of Rare Earth Conversion Coatings on AZ91 Magnesium Alloy

Magnesiumalloysarewidelyusedinweaponin dustry,spacenavigationandhavegoodpotentialof applicationanddevelopmentindailycommunication facilitiesduetotheirpropertiesoflightweightandhighstrength[1].Appliedasstructuralmaterials,mag nesiumalloysmayeasilycrackduet…     

Effect of Rare Earth Elements on Thermal Fatigue Property of Low Chromium Semi-Steel

The effect of rare earth elements on eutectic carbide‘s morphology of low chromium semi-steel in as-cast state and after heat treatment was investigated, and accordingly, the thermal fatigue property of this material was studied. The results show that RE can improve the eutectic carbide‘s morphology, inhibit the formation and propagation of thermal fatigue cracks, therefore, promote the thermal fatigue property, which is more noticeable in case of the RE modification in combination with heat treatment. The optimal thermal fatigue property can be obtained when treated with 0.2% RE modification as well as normalization at 950℃ for 3h.     

包头稀土精矿添加25%碳酸钠焙烧反应动力学研究

采用XRD、DTA-TG及化学分析等方法,对包头稀土精矿添加25%碳酸钠焙烧反应进行了研究。分解反应分两个阶段进行,第一阶段348℃～455℃,稀土氟碳酸盐分解为稀土氟氧化物,铈被氧化得到CeO     

Effect of Rare Earth on Microstructure of γ-TiAl Intermetallics

The rare earth (RE) elements (Ce, La) were added to binary Ti-47% Al alloys (atomic fraction) by Induction Skull Melting. The element Ce of 1.0 atomic percent was added individually, and La of 0.2 atomic percent was added individually. This article studied the influences of rare earth metal (Ce, La) on microstructure of as-cast TiA1 based alloy by XRD, SEM, EMPA and TEM measurement methodology. The results show that most of rare earth-rich phases (AlCe, Al-La) are uniformly distributed in grain boundary in the shape of discontinuous network, and some particles of rare earthrich phases within the grains are mainly ellipsoids. In addition, rare earth element can obviously refine the grain size and the lamellar thickness of as-cast TiAl based alloy samples. The grain size of Ti-47Al-1.0Ce-0.2La alloy reaches about 30～80μm, and the lameUar thickness of its γ phase and α2 phase are less than 200 and 20nm, respectively.     

Effect of Rare Earth Elements on Kinetics of Salt Bath Vanadizing

Effect of Rare Earth Elements on Kinetics of Salt Bath Vanadizing     

Effect of Rare Earth Elements on Erosion Resistance of Nitrocarburized Layers of 38CrMoAl Steel

Effect of rare earth elements (RE) on erosion resistance of nitrocarburized layer of 38CrMoAl steel was investigated. The results indicate that significant improvement occurs in erosion resistance of nitrocarburized 38CrMoAl steel by introducing RE during nitrocarburizing processing as compared with conventional nitrocarburizing processing. Results of mechanical testing show that both hardness and impact toughness of RE-nitrocarburizing layer of 38CrMoAl steel increase as compared with the conventional one. Optical microscopy reveals that there is improvement in the nitrocarburized layer attributed to the introduction of RE, which results in improvement in erosion resistance. Surface morphology observation of tested samples reveals that predominantly furrow-like peelings from plastic deformation are observed for RE nitrocarburizied 38CrMoAl steel, while the furrow-like peeling with initial cross crack and large grinding peelings were observed for conventionally nitrocarburized samples.     

Modification Mechanism of Rare Earth Elements in ZA27 Casting Alloys

The model of the liquid-phase ZA27 alloys was set up by molecular dynamics theory. The atomic structure of phase, RE-compounds, and the phase-liquid interface in ZA27 alloys were constructed by computer programming. Electronic structures of phase with rare earth elements dissolved and of phase-liquid interfaces with rare earth elements enrichment in ZA27 casting alloys were investigated by using the Recursion method. The ESE energy of RE elements and the structure energy of RE-compounds, phase, and the liquid-phase ZA27 alloys were calculated. The results show that rare earth elements are more stable to be in the phase interface than in phase, which explains the fact of very small solid solubility of rare earth elements in phase, and the enrichment in the solid-liquid growth front. This makes dendrite melt and break down, dissociate and propagate. RE-compounds can act as heterogeneous nuclei for phase, leading to phase refinement. All above elucidates the modification mechanism of rare earth elements in zinc-aluminum casting alloys, at electronic level.     

Advances in Rare Earth Application to Semiconductor Materials and Devices

The development of rare earths (RE) applications to semiconductor materials and devices is reviewed. The recent advances in RE doped silicon light emitting diodes (LED) and display materials are described. The various technologies of incorporating RE into semiconductor materials and devices are presented. The RE high dielectric materials, RE silicides and the phase transition of RE materials are also discussed. Finally, the paper describes the prospects of the RE application to semiconductor industry .