Influence of Rare Earth Elements on Microstructure and Mechanical Properties of Cast High-Speed Steel Rolls

The influence of rare earth （RE） elements on the solidification process and eutectic transformation and mechanical properties of the high-V type cast, high-speed steel roll was studied. Test materials with different RE additions were prepared on a horizontal centrifugal casting machine. The solidification process, eutectic structure transformation, carbide morphology, and the elements present, were all investigated by means of differential scanning calorimetry （DSC） and scanning electron microscopy energy dispersive spectrometry （SEM-EDS）. The energy produced by crack initiation and crack extension was analyzed using a digital impact test machine. It was found that rare earth elements increased the tensile strength of the steel by inducing crystallization of earlier eutectic γ-Fe during the solidification process, which in turn increased the solidification temperature and thinned the dendritic grains. Rare earth elements with large atomic radius changed the lattice parameters of the MC carbide by forming rare earth carbides. This had the effect of dispersing longpole M C carbides to provide carbide grains, thereby, reducing the formation of the gross carbide and making more V available, to increase the secondary hardening process and improve the hardness level. The presence of rare earth elements in the steel raised the impact toughness by changing the mechanism of MC carbide formation, thereby increasing the crack initiation energy.

Effects of flaky rare earth oxide additives on the high temperature performance of nickel electrodes

Effects of flaky rare earth oxide additives including Er2O3,Tm2O3,and Yb2O3,Lu2O3 on high temperature and high rate discharge performance of nickel electrodes were investigated.The discharge efficiency at 0.2C reached 96% at 60 oC for electrodes with 1 at.% flaky rare earth oxides.The high rate discharge performance for electrodes with flaky rare earth oxides were improved significantly,for example,discharge efficiency at 5C improved from 50% to 70%.The results showed that the end charging potential of the ...

Effect of Rare Earth Elements on Carbide Morphology and Phase Transformation Dynamics of High Ni-Cr Alloy Cast Iron

The effect of rare earth(RE) elements on carbide of high NiCr alloy cast iron was investigated. Meanwhile, the continuous cooling transformation(CCT) curves of cast iron with and without RE addition were determined. The results show that the carbides in high NiCr cast iron can be refined and changed from network and long strip structures into island and block ones. The phase transformation temperature was raised and incubation period of bainite transformation was shortened by adding RE element in high NiCr alloy cast iron.

Effects of Rare Earths and Al on Structure and Performance of High Chromium Cast Iron Containing Wolfram

Effects of RE and Al on the structure, impact toughness, hardness, and wear resistance of high chromium cast iron containing wolfram were investigated. The results show that without modification the volume fraction of austenite is high and the carbide appears to be thick lath and the grain size is relatively large; proper modification using RE combined with Al can reduce volume fraction of residual austenite in the as-cast structure obviously, refine grain size of primary austenite notably, and make the morphology of carbide changing from thick lath to thin lath, rosette, and feather-like modification can also increase hardness, wear resistance and impact toughness of cast iron.

High Temperature Gaseous Rare-Earth Permeation of Polyoxotungstates: An New Effective Method for the Preparation of Tungsten Bronzes

New polyoxometalate α-K 12H 3[Y(BW 11O 39) 2]·25H 2O was synthesized and treated by high temperature gaseous rare earth permeation to prepare tungsten bronze K 0.475WO 3. XRD, TG-DTA, XPS, 183W-NMR,CV and AC impedance spectra were used to characterize the resulting material. The results of XPS indicate that La has permeated and diffused into the body of the sample and exists in the forms of binding with other components. The crystal structure parameters of K 0.475WO 3 were obtained by the analysis of XRD, which shows tetragonal crystal system with lattice parameters: a=12 28 nm, c=3.833 nm, V=578.48 nm -3. The conductivities calculated from the results of AC impedance spectra of the material increase with the increasing of temperature, which shows a semiconductor character.

Microstructure of Surface Layer Formed at Low Temperature and High Carbon Concentration Carburizing with Rare Earth Element

A suitable carburized microstructure with fine granular dispersed carbides in hypereutectoid zone,ultra fine martensite in matrix and recrystallized austenite to be refined to the grain size of 12～14 has been obtained by a new process,which is a high carbon concentration carburizing with rare earth element at low temperature(860～880℃)in a discontinuous gas carburization furnace.There was not much difference for the microstructure in eutectic zone between this and conventional process.Forming mechanism of granular carbides has been also studied in this paper.

Determination of Trace Impurities of Rare Earth Elements in High Purity Yttrium Oxide by ICPMS

Determination of trace rare earth elements(REEs)in 99. 999% purity yttrium oxide using the inductively coupled plasma mass spectrometric technique (ICPMS) has been developed. Instrumental parameters and factors affecitng analytical results have been studied and then optimized.Samples are analyzed directly following an acid digestion without separation or preconcentration and with limit of detection of 0. 003～0. 02 ng/ml, precision of ±5. 4%(cofficient of variation)and recovery of 90～115%. Correction for isobaric interferences from oxide ions and hydroxide ions is made mathematically. Special internal standard procedures are used to compensate drift in metal:metal oxide ratios and sensitivity. The analytical results of several samples are accurate as compared with inductively coupled plasma atomic emission spectrometry (ICPAES) and spark source mass spectrometry (SSMS).

Rare Earths, Trace Element Characteristics of High-Mg Volcanic Rocks of Yixian Formation in Sihetun West Liaoning Province and Its Apocalypse

The high-Mg volcanic rocks of the Yixian Formation in the Sihetun area have the obvious characteristics of mantie-derived lava in rare earth, trace element characteristics with high Mg # （62 - 70） and high content of compatible elements. In the meantime, the volcanic rocks also have the obvious characteristics of Crust-source material in rare earth, trace element characteristics with high ∑ REE （ 158.78 × 10^-6 - 359.66 × 10^-6 ）, high （La/Yb） N （ 14.61 - 29.60）, high La/Nb（2.37 - 7.52） and high Ba/Nb （67.58- 205.96）, obvious positive anomaly of Pb and negative anomaly of Nb, Ta in trace element spider-gram. In Sr-Nd-Pb isotope the （^87Sr/^86Sr）i ratio is higher than 0.706 and the εNd（ t ） ratio is from - 3.4 to - 13, both reflect enriched Mantle characteristics. The characteristics above of the volcanic rocks combined with the content of Sr, Ba, Y, Yb and the ratio of Sr/Y show that the volcanic rocks have the property of the Sanukite rocks in Setouchi Japan beside subduction zone, and illuminate that the Sanukite rocks can be formed not only in island-arc near subduction zone but also in intro-plate. The analysis indicates that the high-Mg volcanic rocks in the Sihetun area result from the collective function of mantle-derived lava and crust-source materials. The result illuminates that the West Liaoning region is very special in tectonic geochemical background in Cretaceous in East China, and is an ideal region for us to further study the characteristics of magmatic activity as well as the process of Crust-Mantle interaction in Eastern China.

Effect of Rare Earth Alloy Modification on High Carbon Equivalent Gray Cast Iron of Automotive Brake Drum

Effect of rare earth alloy modification on properties and microstructure of high carbon equivalent gray cast iron was investigated.The experimental results show that in the way of mechanical property,when the addition of rare earth alloy is 0.2% and 0.3%,the tensile strength of cast iron increases.In the way of microstructure,the addition of rare earth alloy increases the number of primary austenite dendrites,reduces secondary dendritic arm spacing,and changes the eutectic size and quantity.When rare earth alloy is added into gray cast iron,the morphology and quantity of graphite play a major role on the improvement of tensile strength.

Simultaneous Determination of Trace Rare Earth Elements and Other Elements in High Purity Terbium Oxide (Tb_4O_7) by ICP-AES After HPLC Separation Using P507 Resin

This article describes a new method for the simultaneous determination of trace rare earth elements (REEs) and non rare earth elements (NREEs) in high purity terbium oxide by ICP-AES after HPLC separation using P507 resin. The chromatographic separation of the analytes from the matrix using dilute nitric acid as mobile phase was studied. The experimental results showed that a favorable separation of trace metals (Cu and Gd) from the matrix (Tb) can easily be achieved by elution with dilute nitric acid within 25 min. The proposed method was applied to the determination of trace metals (Ca, Cu, Mg, Mn, Ni, Si, La, Ce, Pr, Nd, Sm, Eu and Gd) in high purity terbium oxide. The detection limits (DLs) for the analytes ranged from 0.4-4.0 μg\5g -1, and the recoveries are from 78%-105%.

Cu-Fe Catalysts Modified by Rare Earths for Preparation of High Alcohols from Fatty Acid Esters Reduction

In order to increase activity of Cu Fe catalyst and use the mixture of nitrogen and hydrogen directly for preparation of high alcohols by reducing fatty acid esters, rare earths were used to modify the catalyst. Experiments show that yield of high alcohols increases by 3% as 1% Sm 2O 3 is added to the catalyst when the reduction is carried out under pure hydrogen. The yield greatly decreases when the reduction is carried out under the mixture of hydrogen and nitrogen. Catalysts activities modified by Y and Nd can be evidently improved and even enhanced. The yields increase by 33% and 29% when 1% Y 2O 3 and 1% Nd 2O 3 are added to the catalyst, respectively.

Effect of Rare Earths on Solidification Microstructure and High Temperature Mechanical Property of Sn60-Pb40 Solder alloy

Trace rare earth elements were used in order to strengthen the Sn60 Pb40 solder alloy. The experimental results show that the high temperature tensile strength of near eutectic Sn60 Pb40 solder alloy is increased by about 70% after adding trace rare earth elements. Analysis shows that the high affinity between rare earth element and Sn leads to the variation of contact angle at the three phase junction of S/L interface during eutectic growth and further changes the Pb concentration at the S/L interface needed for coupled eutectic growth. Thus the eutectic microstructure can directly grow upon the primary Pb rich phase and the formation of coarse Sn rich halo is suppressed. Therefore homogeneous metallurgical microstructure can be obtained.

Effect of the Rare Earths on the High Temperature Properties of Deformed Leaded-Brasses

The effect of the rare earths on the high temperature properties of deformed leaded-brasses has been stu- died with the high temperature tensile test.The results show that the rare earth additives can increase elongation of alloys at high temperature,but they had little effect on the maximum flow stress.With the help of SEM. X-ray diffraction instrument,quantitative metallography analysis instrument,etc.,the effect of the rare earth elements on the mierostrueture of alloys has also been examined.

Effects of Rare Earths on the Tempering Transformation Kinetics of High Carbon Steel

Effect of rare earth metals (REM) on tempering process and decomposition kinetics of martensite and retained austenite of high carbon steel were investigated by DSC technique,based on the non-isothermal kinetic theory.The result shows that the addition of REM in high carbon steel increases the decomposition temperatures of martensite and retained austenite,decreases the thennal effect values,elevates the activity energies and changes the transformation mechanism.

Effect of Rare Earth Elements on Thermal Fatigue of High Ni－Cr Alloy Cast Iron

The effect of RE on crack forming and developing of hot rolled high Ni-Cr alloy cast iron during thermal fatigue test was investigated.It shows that the serviceable life of hot rolled high Ni-Cr alloy cast iron can be improved by RE.The number of cycle before fracture was increased by 42%～163%.The optimum of RE addition is 0.05 wt%～0.15wt%.

Determination of Non-Rare Earth Impurities in High Purity Lanthanum Oxide by Inductively Coupled Plasma Atomic Emission Spectrometry after HPLC Separation Using P507 Resin

A new method for the determination of trace non-rare earth elements (NREEs) impurities in high-purity lanthanum oxide by HPLC combined with ICP-AES is proposed. The chromatographic retention behaviors of matrix (La) and NREEs were studied using 2-ethylhexyl hydrogen 2-ethylhexyl phosphonate (P507) chelating resin as the stationary phase and dilute nitric acid as the mobile phase. It is found that the use of pH 1.7 nitric acid enables effective elution of NREEs from HPLC column, but the lanthanum remains on the column. The experimental results show that a favorable separation between matrix lanthanum and NREEs can be obtained within 15 min. The method proposed is applied to the determination of 8 NREEs impurities in high-purity La2O3. The recoveries of 8 NREEs are in the range of 90 % similar to 110 %.

Mechanism of Action of Rare Earths in High Effective Fe Powder Welding Rods

The optimum coating composition of alkali Fe powder welding rods was designed by orthogonal experiment with mix rates. A new kind of effective RE-Fe powder welding rod was prepared which could be used at the condition of direct and indirect current. The arc characteristics and stabilities of effective Fe powder welding rods containing RE were analyzed by HANNOVER analyzer. The efficiency of Fe powder welding rods was tested by weighting method. It was found that the stability of Fe powder welding rods was improved when it was added with rare earths. The results of impact experiment at low temperatures and SEM analysis on impact break showed that the grain was refined, the welding joint was cleaned, and the mechanical properties of joint was enhanced with proper RE content. It was provided with good processing property for this effective RE-Fe powder welding rod, and its efficiency could arrive at 180%.

Effect of Rare Earth Elements on Low Frequency Fatigue of Hot Rolled Steel 60CrMnMo at High Temperature

The effect of rare earth(RE) on low frequency high temperature fatigue strength of hot rolled steel 60CrMnMo was investigated. The results show that by adding a certain amount of RE in steel 60CrMnMo, its serviceable life during low frequency fatigue test at high temperature can be improved.The number of cycles for fracture was increased by 18.5%～28.8%. The number of large inclusion particleswas reduced and the composition of inclusions and their shape were changed as well. The strip distances on fatigue fracture surface were decreased. It is concluded that the optimum amount of RE addtion is about 0.05 wt%～0. 10 wt%.

Layer Structure Analysis of Low-Carbon Steel Containing Rare Earth by High-Temperature Carburizing of Liquid Cast-Iron

The layer structure of low-carbon steel containing RE by high-temperature (T>1200 ℃) carburizing of liquid cast-iron was studied and the diffusion activation energy of carbon was calculated by metallographic microscpe, chemical analysis etc. The result shows that the technology of carburizing in liquid cast-iron can expedite caburization distinctly and changes the carburizing layer structure. The carburizing rate is 60～80 times of that of the traditional technology, and there is about 43% decrease in the activation energy compared with gas-carburization. In outer structure layer, cementite is formed simultaneously both on the crystal boundary reticularly and inside the crystal grains stripedly. In inner carburizing layer, there is undissolved blocky ferrite in reticular cementite. Besides, rare earth element can expedite carburization process.