Effect of rare earth additives on alumina fiber development in Ti-Al intermetallic matrix composites

Al2O3(f)/TiAl composites were synthesized by an exothermic reaction method using Ti,Al and TiO2 powders doped with Nb2O5 and La2O3. The effect of Nb2O5 and La2O3 additives on the growth and morphology of the fibers, the phases and microstructure of the composites were investigated by means of XRD and SEM. The result indicates that the in situ alumina fiber can be developed in Ti-Al matrix with the Ti/Al mole ratio of 1:2-1:7, and the addition of rare earth powders can improve the dispersion of the fibers in the matrix and increase the length-to-diameter ratio of the fibers.

Effect of Rare Earth Additives on Chrome-Plating Quality

The effect of rare earth additives used in chrome-plating on the electroplated coating behaviors of the luminosity, brightness, dispersibility of plating solution, deposition rate of ion and current efficiency were studied systemically by means of measuring cathode current at 20 and 50 ℃ respectively. The results show that rare earth additives increase the luminosity and brightness of the electroplated coating, dispersibility of plating solution, deposition rate of ion and current efficiency at 50 ℃. At 20 ℃, rare earth additives only increase the current efficiency and ion deposition rate. The most effective rare earth oxides additives are Pr6O11 and CeO2.

Effect of Rare Earth Fluoride Complex Additives on Properties of Steel

A technique of treating steel with rare earth fluoride complex additives(REFCA),effects and influnce factors have been studied.REFCA play a role on controlling inclusion morphology,purifying the molten steel and improving properties of steel.The optimum composition of REFCA is REF_3 42%;CaO 33%;SiCa 25%,and the amount of REF_3 is 0.5 wt%～0.6 wt% of steel.

Effect of rare earth samarium addition on the kinetics of precipitation in Al-Cu-Mn casting alloy

The mechanical properties of Al-Cu-Mn casting alloy mainly depend on the morphology, distribution, size, and number ofθ′（Al2Cu） precipitates. In this study, we have analyzed the effect of rare earth samarium （Sm） addition on the kinetics of precipitation in the Al-Cu-Mn casting alloy by using differential scanning calorimetry （DSC） and high-resolution transmission electron microscopy. Thermal ef-fect peaks that are attributed to the formation and the dissolution of Guinier-Preston （GP） zone andθ′phase were identified from the DSC curves. The activation energy ofθ′formation was calculated by using both the Kissinger method and the analytical model, and the corre-sponding results were compared. Results suggest that the activation energy ofθ′formation in Al-Cu-Mn alloy is dramatically higher than that in Al-Cu-Mn-Sm alloy. Accordingly, it is concluded that the addition of rare earth Sm decreases the activation energy ofθ′formation and promotes the formation ofθ′precipitates.

Microstructure and corrosion behavior of as-cast ADC12 alloy with rare earth Yb addition and hot extrusion

The effects of rare earth ytterbium(Yb)addition and hot extrusion on the microstructure and corrosion behavior of as-cast ADC12 were studied by optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD).The experimental results demonstrate that both the Si phase andβ-Al5FeSi phase in the alloy with 0.9 wt%Yb have been remarkably refined,and the Al3Yb intermetallic compound has also been obtained.The Si,β-Al5FeSi,and rare earth phases are further refined in the alloy at 0.9 wt%Yb and hot extrusion.The results of the immersion corrosion tests and electrochemical experiments show that the corrosion current density(8.56μA/cm2)of the alloy with 0.9 wt%Yb addition and hot extrusion is 50.6%lower than the untreated alloy(17.33μA/cm2),and the polarization resistance(9252Ω·cm2)was 71.3%higher than the untreated alloy(2654Ω·cm2).The corrosion in the cathode phase in the micro-battery was refined to varying degrees attributable to the addition of Yb and hot extrusion,where the cathode reaction in the corrosion process caused a decrease of the corrosion rate.

Preparation of cerium oxide based environment-friendly chemical conversion coating on magnesium alloy with additives

Ce（SO4）2？H2O2 solution was adopted to prepare a chemical conversion coating on AZ91D magnesium alloy.Additives of Ni（NO3）2 and sodium dodecyl benzene sulfonate were applied to improving the coating formation.SEM,EDS,XRD and GIXD were adopted to study the coating morphology,structure and composition,and the potential change curve in the treating solution was recorded to study the coating growth.Sodium dodecyl benzene sulfonate makes a remarkable improvement in the coating compactness,and shortens the time in the second stage of the coating formation from 5 min to 2 min.Compared to Ni（NO3）2,sodium dodecyl benzene sulfonate makes the more remarkable effect on the corrosion resistance improvement,since it can decrease the current density of corrosion from 7.41×10-5 A/cm2 to 2.20×10-5 A/cm2.The additives of Ni（NO3）2 and sodium dodecyl benzene sulfonate can enhance the Ce content from 18.92% to 22.32% and 25.08% in the coating,respectively.The XRD and GIXD results indicated that all the conversion coating formed in different solutions exhibit amorphous structure.

Perspective and Prospects for Rare Earth Permanent Magnets

Rare earth permanent magnets constitute a mature technology,but the shock of the 2011 rare earth crisis led to the re-evaluation of many ideas from the 1980s and 1990s about possible new hard magnets containing little or no rare earth(or heavy rare earth).Nd-Fe-B magnets have been painstakingly and skillfully optimized for a wide range of applications in which high performance is required at reasonable cost.Sm-Co is the material of choice when high-temperature stability is required,and Sm-Fe-N magnets are making their way into some niche applications.The scope for improvement in these basic materials by substitution has been rather thoroughly explored,and the effects of processing techniques on the microstructure and hysteresis are largely understood.A big idea from a generation ago-which held real potential to raise the record energy product significantly-was the oriented exchange-spring hard/soft nanocomposite magnet;however,it has proved very difficult to realize.Nevertheless,the field has evolved,and innovation has flourished in other areas.For example,electrical personal transport has progressed from millions of electric bicycles to the point where cars and trucks with electrical drives are becoming mainstream,and looks ready to bring the dominance of the internal combustion engine to an end.As the limitations of particular permanent magnets become clearer,ingenuity and imagination are being used to design around them,and to exploit the available mix of rare earth resources most efficiently.Huge new markets in robotics beckon,and the opportunities offered by additive manufacturing are just beginning to be explored.New methods of increasing magnet stability at elevated temperature are being developed,and integrated multifunctionality of hard magnets with other useful properties is now envisaged.These themes are elaborated here,with various examples.

Effect of Additive on Microstructure of Transparent YAG Ceramics

Transparent YAG (yttrium aluminum garnet) ceramics were fabricated by solid-state reaction method. Effect of additive (tetraethyl orthosilicate, TEOS) on microstructure of YAG ceramics was investigated. If the addition of TEOS is more than 3% (mass fraction), large amount of liquid phase can be yielded at grain boundaries, resulting in the formation of second phase particles at grain boundaries. If the addition is less than 0.05% (mass fraction), pores are entrapped in the grains. The suitable amount is 0.5% (mass fraction). A fully transparent YAG ceramic was fabricated by vacuum sintering at 1700 ℃ for 5 h. Optical transmittance of the YAG ceramic is 63% in the visible light wavelengths and 70% in the infrared wavelengths.

A yttrium-containing high-temperature titanium alloy additively manufactured by selective electron beam melting

A yttrium-containing high-temperature titanium alloy(Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si-0.1Y, mass fraction, %) has been additively manufactured using selective electron beam melting(SEBM). The resulting microstructure and textures were studied using scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and electron backscattered diffraction(EBSD) and compared with the conventionally manufactured form. A notable distinct difference of microstructures is that additive manufacturing by SEBM enables homogeneous precipitation of fine Y2O3 dispersoids in the size range of 50-250 nm throughout the as-fabricated alloy, despite the presence of just trace levels of oxygen(7×10-4, mass fraction) and yttrium(10-3, mass fraction) in the alloy. In contrast, the conventionally manufactured alloy shows inhomogeneously distributed coarse Y2O3 precipitates, including cracked or debonded Y2O3 particles.

Effect of rare earth and Mn elements on the corrosion behavior of extruded AZ61 system in 3.5 wt%NaCl solution and salt spray test

In this study,multiple addition of rare earth(RE)and manganese(Mn)to AZ61 was conducted aiming to find out the influence to corrosion resistance.AZ61 containing different amounts of RE and Mn was investigated by electrochemical measurement in condition of 3.5 wt%NaCl solution at 25°C.Gravimetric measurement was conducted in 5 wt%salt spray at 35°C and 3.5 wt%NaCl solution at 25°C.Samples were characterized by SEM,EDS,OM and XRD.The result shows that with RE addition Al8Mn5 in AZ61 changed into Al10RE2Mn7.The quantity ofβphase is reduced significantly.The multiple addition of RE and Mn improved the corrosion resistance of AZ61.When the ratio of Mn and RE is 0.3,alloy has the best property of corrosion resistance.In addition,the composite addition removed the impurity elements in AZ61 especially Fe.

Status of Applications of Rare Earth Metals to Precision Alloys

Rare earth resources in China are the most abundant, the production capability ranks second in the world. The first generation of rare earth-transition group permanent magnet alloy RECo5 developed in 1970's started using rare earths as substantial components. Because of the need of product diversity and to utilize rich resources of mixed rare earth metals, researchers are working on substitution of expensive elemental rare earth metals with cheaper cerium or mixed rare earths (rich in cerium, lanthanum or neodymium) to make lower cost permanent - magnet such as CeCo5. Ce[CoCuFe]5. etc.

Study on Preparation and Engine Bench Test of Friction-Reducing and Repairing Additive to Lubricating Oils

A new kind of friction-reducing and repairing additive containing nano-scale copper and rare earth compounds were prepared by means of synthesis and compounding methods. The performance of the said additive was investigated by engine bench test, and was compared to the performance of similar domestic and imported additives. The deterioration of lube oils containing additives over different time intervals was studied by means of plasma spectrometry and mass spectrometry, and the effect of additive package on engine power was also studied. Test results have revealed that the synthetic additive package can provide good anti-wear performance to the tribo-pairs. In particular, after 300 hour application of the said additive package the connection rod shaft and copper sleeve showed 'zero wear' to achieve the in situ dynamic repairing of tribo-pairs. Application of the said synthetic additive can effectively improve the engine power performance and extend the engine service life.

TC4表面掺La微弧氧化涂层的显微结构与耐磨性的研究

针对TC4钛合金在服役期间耐磨性较差等问题,本文在乙酸钙-六偏磷酸钠电解液体系下运用微弧氧化工艺在TC4钛合金表面制备出掺La陶瓷涂层。重点研究了电解液中掺杂La(NO_(3))_(3)对TC4钛合金微弧氧化涂层(MAO)耐磨性的影响。利用XRD、SEM、显微硬度计、摩擦磨损试验机、涂层附着力划痕仪等仪器对不同La(NO_(3))_(3)掺杂量下的微弧氧化涂层的物相组成、微观形貌、厚度、显微硬度、摩擦因数、结合力等指标进行表征。结果表明:随着La(NO_(3))_(3)掺杂量增加,MAO涂层由HAp、A-TiO_(2)、R-TiO_(2)、La_(2)O_(3)相组成。掺La陶瓷涂层厚度虽略有减小,但致密性有所提高。涂层的显微硬度先增大后减小、摩擦因数先减小后增大。当La(NO_(3))_(3)掺杂量为6 g/L时,涂层显微硬度提高31.18%,涂层与基体结合力提高30.59%,MAO涂层摩擦因数最小,约为0.55。

稀土Y元素对CuAlMn形状记忆合金晶粒细化及其力学性能的影响

CuAlMn形状记忆合金具有优良的耐热稳定性和高阻尼特性,在多种领域有着明确的目标需求,然而,晶粒粗大易导致沿晶断裂,严重弱化了合金的力学性能。为改善合金力学性能,引入了稀土Y元素,采用电弧熔炼吸铸炉制备了Cu-11.36Al-5Mn-xY(x=0~3,质量分数/%,下同)系列铸态合金,又经固溶时效对合金微观组织进行了调控和均质化。采用DSC、XRD、金相和SEM对合金的相变、物相、微观组织结构进行了表征。通过显微硬度计和万能材料试验机测试了合金的硬度和力学性能。结果表明,Y元素添加可有效细化CuAlMn合金晶粒,晶粒尺寸从数百微米下降至10μm左右,同时伴随着大量网格状含Y析出相沿晶析出,冷却过程中晶粒形核区的增多和生长受到抑制是晶粒细化的主要因素。合金硬度随Y元素添加量的增大而升高,这与合金中大量含Y硬脆相的析出有关,Y含量越高,析出相体积分数越高,此外,固溶时效态样品硬度高于铸态样品,源于固溶时效态样品析出相在整个基体内的分布和更高的析出相体积分数。合金的压缩强度和拉伸断裂强度在Y元素含量为0.1%~0.4%时得到明显提升,其强化机制可通过细晶强化、沉淀强化和固溶强化来理解。合金压缩断裂应变在Y元素含量为0.4%时达到最大,断后伸长率在Y元素含量为0.1%时达到最大,其变化趋势与晶粒细化和沉淀析出相的耦合效应有关。

氮添加对稀土尾砂地猴樟幼苗根系生长、生物量分配及非结构性碳水化合物的影响

为探究氮添加对稀土矿尾砂地猴樟(Cinnamomun bodinieri)幼苗生长及非结构性碳水化合物(NSC)含量的影响,以1年生猴樟扦插苗为研究对象,选用硝酸铵钙作为氮肥(含N 15%),设置3种氮肥水平(CK(0)、N1(1.8 g·株^(-1))、N2(3.6 g·株^(-1))),分析不同氮添加水平下猴樟幼苗根系生长、生物量分配和NSC等指标的差异,探讨稀土尾砂地猴樟对氮添加的响应。结果发现:稀土尾砂地氮添加均增加了猴樟幼苗不同组织的生物量积累,其中N1处理下叶生物量、冠层生物量分别较N2处理下显著提升了44.75%、57.43%(P<0.05);N2处理下叶比重分别较CK、N1处理显著提升了123.53%、15.85%(P<0.05)。不论是粗根(直径>2 mm),还是细根(直径≤2 mm),氮添加均显著增加了植物的根长和根表面积(P<0.05),其中N1处理的促进效果最显著(P<0.05);N2处理下的比根长、比表面积均高于CK与N1,且与CK显著差异(P<0.05)。对NSC来说,N1处理提升了叶、茎中的可溶性糖质量分数,而N2处理下细根NSC质量分数分别比CK、N1显著降低了46.49%、28.61%。综上,在稀土矿尾砂地植被恢复过程中,宜选用1.8 g·株^(-1)硝酸铵钙氮肥对猴樟幼苗进行施肥管理。

稀土氧化物对低温固相合成镁铝尖晶石纤维的影响

为探究稀土氧化物和合成温度对合成镁铝尖晶石纤维的影响,以碱式硫酸镁晶须、铝溶胶为主要原料,分别以Y_(2)O_(3)、La_(2)O_(3)、Nd_(2)O_(3)为添加剂,经不同温度热处理后,制备了镁铝尖晶石纤维,研究了添加剂的种类(Y_(2)O_(3)、La_(2)O_(3)、Nd_(2)O_(3))、加入量(加入质量分数分别为0、1%、2%和3%)以及不同热处理温度(800、1000和1200℃保温3 h)对低温固相合成镁铝尖晶石纤维的影响。结果表明:1)以碱式硫酸镁晶须、铝溶胶为原料,添加质量分数为3%(w)的Nd_(2)O_(3)或Y_(2)O_(3)在800℃热处理时均对镁铝尖晶石纤维的合成具有较为明显的促进作用。2)热处理温度为1000℃时,添加3%(w)Nd_(2)O_(3)合成镁铝尖晶石纤维的效果最好。

耐热铝合金的研究进展及展望

铝合金的热稳定性决定了合金材料在高温条件下长时间保持性能的能力,热稳定性已成为铝合金研究领域的热点。提高铝合金热稳定性将显著提升其应用范围。结合国内外研究现状,重点总结合金元素的作用机理、耐热铝合金的设计理论及成形技术方面已经取得的进展。通过阐述过渡金属和稀土金属改善铝合金热稳定性的微观结构机理,系统阐明了耐热铝合金的先进制备工艺,如快速凝固、粉末冶金和增材制造等工艺,并对耐热铝合金的发展趋势进行探讨,为我国耐热铝合金的发展提供借鉴和参考。

稀土钢工业生产中稀土收得率影响因素分析

稀土钢工业化生产过程中涉及稀土收得率问题,稳定的收得率是稀土钢产品性能稳定的重要保证。通过钢包添加稀土、中间包取样分析,研究了添加工位、添加量和钢液成分(氧活度、硫含量)对稀土钢稀土收得率的影响。结果表明,在钢包、中间包、结晶器添加稀土,稀土收得率依次提高;在LF钢包离位前添加稀土合金,添加量越大,收得率越低;钢液中氧、硫含量越高,稀土收得率越低。

硫酸高铈添加剂对超薄电解铜箔结构和力学性能的影响

为提升超薄电解铜箔的力学性能,通过在电解液中添加不同质量浓度的硫酸高铈,研究其对超薄电解铜箔结构和力学性能的影响。结果表明:当Ce(SO_(4))_(2)质量浓度为15 mg/L时,所制备的超薄电解铜箔抗拉强度为457 MPa,延伸率为5.23%,较未添加的电解铜箔抗拉强度和延伸率分别提升了16%和78%,这是因为Ce(SO_(4))_(2)的加入增大了铜电沉积过电位,加快了铜离子在阴极表面扩散速率,Ce^(4+)为Cu^(2+)的沉积提供了活性位点,使得铜晶核大量生成,抑制铜晶体生长,细化铜晶体晶粒大小。Ce(SO_(4))_(2)的加入可改善超薄电解铜箔形貌结构以及提升其力学性能。

Microstructure and corrosion resistance of sintered NdFeB magnet modified by intergranular additions of MgO and ZnO

Microstructure and corrosion resistance of sintered Nd15Dy1.2Fe77Al0.8B6 and Nd22Fe71B7 magnets modified by intergranular addition of MgO and ZnO were investigated. Both the remanence and sintering density of the magnets increased slightly with intergranular additions of MgO and ZnO. There was a remarkable increase in coercivity of Nd22Fe71B7 after addition. Besides, the effects on magnetic properties and an improved corrosion resistance were observed. Compared with the native magnets without addition, corrosion potential of the magnets with MgO and ZnO additives was more positive and the current density in the anodic branch of the polarization curve was reduced. Corrosion resistance resulting from autoclave testing （2×10^5 Pa of steam pressure, 120 ℃） showed that the corrosion rate of NdFeB magnets reduced with the increase of additive amount. Microstructure observation revealed that MgO and ZnO additives were incorporated into the intergranular phases in the magnets. With the introduction of MgO and ZnO, more intergranular phase with high oxygen content was formed while keeping the volume fraction of all the intergranular phases almost unchanged, which may contribute to improved corrosion resistance. Furthermore, addition of MgO and ZnO refined the grain size of Nd22Fe71B7.