冷却速度对稀土锌合金凝固组织和性能的影响

研究了锌铝铜三元共晶合金中冷却速度对稀土锌合金的凝固组织和性能的影响。研究结果表明，稀土能细化锌合金的凝固组织和改善其机械性能，这些效果均受冷却条件的影响；冷却速度大，效果显著。但是，稀土锌合金的塑性比未加稀土的锌合金略低。在不同冷却条件下，锌合金中的稀土最佳加入量可能有所不同。     

稀土在ZGCr20RE半热滑轨中的应用研究

本文简述了大型推钢式加热炉用滑轨的使用条件、技术要求和国内外及我厂有关滑轨材质选择与使用概况;介绍了ZF3G20RE钢的稀土加入量及回收率的方法、稀土对ZG3Cr20耐热钢机械性能、抗氧化性、耐磨性和铸造性及金相组织的影响;报告了稀土对该钢种凝固机理等不同的试验研究成果.介绍厂其试验方法,给出了该钢种不同稀土加入量的热分析曲线、常规凝固单向凝固和定向凝固的结晶组织.据此进一步论述了稀土对该钢种有细化晶粒、改善铸造性能和细化枝晶臂及减小元素偏析的良好作用.本文介绍了包钢使用ZG3Cr20RE耐热钢半热滑轨年经济效益约为200余万元的具体经济分析.     

稀土在双相不锈钢中的应用研究

就国内外稀土在铁索体+奥氏体双相不锈钢中的应用研究作了简单介绍,包括稀土对双相不锈钢的凝固组织、耐腐蚀性能和力学性能的影响,并探讨了稀土在双相不锈钢中的发展前景.     

Ce对A14.5Cu合金流动性和热裂倾向的影响

研究加入稀土Ce对A14.5Cu合金流动性、凝固收缩、微观组织和热裂倾向的影响.结果表明,适量稀土ce的加入,降低金属液的黏度,提高合金流动性,减少金属在凝固过程中的收缩,抑制合金枝晶化的趋势,改善铸造合金的微观组织,净化合金,提高合金的导热率,明显地减少合金的热裂倾向.稀土Ce加入量为4%时,A14.5Cu合金流动性最佳、凝固收缩量最小、合金晶粒组织细化圆整,同时其热裂倾向最小.     

Ce对Al4.5Cu合金流动性和热裂倾向的影响

研究加入稀土Ce对Al4.5Cu合金流动性、凝固收缩、微观组织和热裂倾向的影响。结果表明,适量稀土Ce的加入,降低金属液的黏度,提高合金流动性,减少金属在凝固过程中的收缩,抑制合金枝晶化的趋势,改善铸造合金的微观组织,净化合金,提高合金的导热率,明显地减少合金的热裂倾向。稀土Ce加入量为4%时,Al4.5Cu合金流动性最佳、凝固收缩量最小、合金晶粒组织细化圆整,同时其热裂倾向最小。     

稀土对Fe-36Ni因瓦合金凝固组织和铸态热塑性的影响

通过真空感应炉和Gleeble—3800热模拟试验机研究了稀土对Fe-36Ni因瓦合金凝固组织和铸态热塑性的影响。结果表明:添加0.12%Ce+0.06%La混合稀土后,合金凝固组织显著细化,柱状晶变细变短,生长形态由直线状生长变为网篮状交错生长,等轴晶比例达40%。但添加0.12%Ce+0.06%La混合稀土后,合金在850~1 200℃温度区间的铸态热塑性严重恶化,这主要是由于在晶界上生成了大量Fe-Ni-Ce-La稀土晶间脆性相,削弱了晶界结合力,阻止了晶界移动,以致合金热塑性的恶化。     

稀土处理C-Mn钢显微组织和夹杂物演化

对稀土处理C-Mn钢的夹杂物和显微组织进行分析,统计稀土处理C-Mn钢中针状铁素体形核核心尺寸,并将稀土处理钢在不同温度下淬火,研究稀土夹杂物生成和长大过程.实验结果表明:C-Mn钢加入少量稀土后钢中夹杂物从MnS＋硅铝酸盐夹杂转变为La₂O₂S＋LaAlO₃＋MnS＋硅铝酸盐夹杂,尺寸得到细化,显微组织也从马氏体＋贝氏体组织变成侧板条铁素体、针状铁素体和块状铁素体组织;稀土处理C-Mn钢中针状铁素体有效形核核心的尺寸集中在1~4μm,主要是在钢液中形成,冷却和凝固过程形成的数量较少;稀土夹杂物在钢液温度和冷却及凝固过程容易碰撞黏合长大,上浮从钢液中去除,MnS能在稀土夹杂物颗粒间析出.      

稀土La对(Ag-Cu_(28))-25Sn-xLa合金微观结构及凝固机制的影响

研究了稀土La对(Ag-Cu28)-25Sn-xLa合金微观结构的影响,并探讨了稀土La含量的变化在其凝固过程中的作用。采用高频感应加热熔炼,经水淬制得(Ag-Cu28)-25Sn-xLa合金。通过XRD,SEM,EDS等分析手段,研究了合金的物相组成、凝固组织及元素分布情况。研究结果表明:微量的稀土La足以改变(Ag-Cu28)-25Sn合金的凝固过程;La含量不大于0.5%时,合金的物相组成为Ag3Sn,Cu3Sn和Cu6Sn5相;当La含量不小于1.0%(质量分数)时,合金的物相组成为Ag3Sn和Cu3Sn;同时,随La含量的增加合金的凝固组织不断细化,且有利于Ag(Sn)固溶体初生相的析出。     

超声波作用下不同添加剂对高碳钢凝固组织的影响

 主要研究了在超声波作用下不同添加剂对高碳钢凝固组织的影响。结果表明：在超声波作用下,高碳钢液中添加钛铁、铈可以明显细化其凝固组织,但是添加铝对其凝固组织的细化作用不明显。高碳钢凝固组织的细化是由于Ti（C,N）可以作为非均质形核的核心,促进高碳钢液凝固过程的形核,Ti（C,N）有效的钉扎晶界作用,阻止初生奥氏体晶粒的长大;超声空化作用下稀土氧化物、氧硫化物数量的增多,增加了高碳钢液凝固过程中非均质形核核心的数量。     

稀土La对(Ag-Cu8)-25Sn-xLa合金微观结构及凝固机制的影响

研究了稀土La对(Ag-cu28)-25SnxLa合金微观结构的影响,并探讨了稀土La含量的变化在其凝固过程中的作用.采用高频感应加热熔炼,经水淬制得(Ag-Cu28) -25Sn-xLa合金.通过XRD,SEM,EDS等分析手段,研究了合金的物相组成、凝固组织及元素分布情况.研究结果表明:微量的稀土La足以改变(Ag-Cu28) -25Sn合金的凝固过程；La含量不大于0.5％时,合金的物相组成为Ag3Sn,Cu3Sn和Cu6Sn5相；当La含量不小于1.0％(质量分数)时,合金的物相组成为Ag3Sn和Cu3Sn；同时,随La含量的增加合金的凝固组织不断细化,且有利于Ag(Sn)固溶体初生相的析出.     

Effect of Cerium on the Properties of CuPNiSn Amorphous Alloys

CuPNiSn amorphous alloys are good brazing materials at medium temperature for replacementof silver bearing brazing materials.The crystallization temperature,wettability,tensile strength of Cu-Cujoints and the microstructure of joints for three compositional series are reported.Some rare earth elementswere added in two series.It has been found that grains are refined and the tensile strengths increase as in-creasing rare earth content.The results also show that the brittle fracture turns to plastic one for the jointswith reducing amount of(Ni+Sn),and the tensile strength is increased.     

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.     

微生物技术在稀土资源利用中的研究进展

主要介绍了稀土资源的重要作用及利用现状,对我国的稀土矿分布及特征进行概述,并提出稀土开采存在的问题及微生物采矿的优势。回顾利用微生物进行稀土矿开采的发展进程,总结其研究进展,介绍微生物采矿作用机理的研究,主要包括微生物浸出、吸附和积累稀土元素机理的相关研究,以及稀土矿采矿微生物的分离方法及种属分布等。以中国白云鄂博矿床和澳大利亚Mount Weld矿床中的矿石为例,说明微生物对矿石中稀土元素的提取作用。简述微生物对废弃物中稀土元素的回收作用,及微生物利用稀土元素技术将面临的挑战,并对其未来进行了展望。      

Influence of Light Rare Earth on Toughness of Welded Seam of LAHS Steel

The influence mechanism of light rare earth elements, which are transited to the welding seam of low-alloy high strength (LAHS) steel through the covering of the electrode, on the toughness of the welding seam was studied. The experimental results show that proper amount of rare earth elements can desulfurate, dehydrogenate, reduce inclusions and purify the structure of the welding seam. Rare earth element additions have .the effect on welding seam and, at the same time, the transformation of side-batten ferrite is resisted while the pin-ferrite structure is promoted. The improvement of the toughness of the welding seam is due to the purifying action of rare earth elements as well as their refining effect on the structure. However, the toughness of the welding seam can decrease when the amount of light rare earth elements are added excessively because the crystal grains become coarser, porosities appear and the inclusions increase as well. The experimental results show that the suitable amount of light rare earth element additions is about 2%.     

Microstructural design in LaCe misch-metal substituted 2:14:1-type sintered magnets by dual-alloy method

LaCe-based sintered magnets with different microstructural features and distinct rare earth elemental distribution were designed by dual-alloy method.The sample prepared by fine LaCe-containing powder and coarse LaCe-free powder possesses higher remanence(~13.41 kGs),whereas another sample prepared by fine LaCe-free powder and coarse LaCe-containing powder possesses higher coercivity(~5.67 kOe).Additionally,these samples are with the same nominal compositions and their elemental distribution features are obviously different in matrix grains respectively.Their remanence difference is mainly affected by the saturation magnetization difference caused by the distribution variation of the rare earth elements at the matrix phase.The coercivity difference is affected by the component of the grain boundary phase between the adjacent grains and the distribution variation of the rare earth elements at the matrix phase.These findings may provide a new prospect for the utilization of LaCe mischmetal in 2:14:1-type permanent magnets.     

Research and Development of Rare Earth Advanced Materials in China

ＲｅｓｅａｒｃｈａｎｄＤｅｖｅｌｏｐｍｅｎｔｏｆＲａｒｅＥａｒｔｈＡｄｖａｎｃｅｄＭａｔｅｒｉａｌｓｉｎＣｈｉｎａＷａｎｇＤｉａｎｚｕｏ（王淀佐），ＷａｎＱｕｎ（万群），ＹａｎｇＹｕｃｈｕｎ（杨遇春）（ＧｅｎｅｒａｌＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅ...     

Rare earth elements: Properties and applications to methanol synthesis catalysis via hydrogenation of carbon oxides

Methanol (CH₃OH) is an important industrial chemical with a wide variety of uses. Industrial methanol synthesis catalysts are typically composed of Cu, Zn, and Al, but the use of catalysts incorporating rare earth elements has been shown to improve the catalytic performance. Due to their unique chemical and physical properties, the use of rare earth elements (scandium, yttrium, and the lanthanides) in catalysis in general has continued to increase over the past few decades, while the use of rare earth in methanol synthesis catalysts has not, despite often improving performance. The ability of several of the rare earth elements (Pr, Ce, Eu, Tb, Yb) to easily switch between oxidation states makes them beneficial for many different types of catalysts. However, for methanol synthesis the surface basicity is an important property, and the basic nature of the rare earth elements can be used to tune the basicity of catalysts. A small number of correlations between rare earth properties and catalytic performance have been observed, but often do not apply to other catalysts. Properties such as strength of basic sites, ionic radius, and electronegativity have been found to correlate with performance results such as activity or selectivity.     

微量稀土在银饰品材料中的作用

为改善银合金饰品材料的抗自然时效软化性能，试验研究了含稀土(钇、铈)低于0．05％的银合金饰品材料。测试了银合金的硬度随变形量、温度及时效时间的变化规律，并用电子探针对银饰品试样进行扫描分析，发现微量稀土能够细化晶粒，并以固溶或第二相形式存在。有效地延缓银合金材料的回复和再结晶，提高了银饰品材料的抗自然时效软化能力。     

非水溶剂电还原制取重稀土金属及合金的研究现状及发展

随着重稀土元素对铝、镁、铜、镍及钢铁等金属材料的功能化作用被广泛关注,使得作为战略性资源的重稀土元素在金属合金材料的应用领域拓展空间巨大.在此背景下,作为改性元素的重稀土金属及合金的市场需求必然猛增.由于重稀土单质自身的高熔点,混熔法、真空热还原法一直是生产制备重稀土金属及合金的主要方法,寻求一条低成本、高效、绿色的制备方法则至关重要.由于熔盐电化学还原法在生产低熔点轻稀土及合金工艺方面具有经济、高效等优势,近年来,通过熔盐电解方式直接制取低熔点的重稀土合金成为国内外学者研究的热点,从目前取得进展来看,具有广阔的发展前景.针对国内外重稀土金属及合金的熔盐电解法制取的研究现状进行了评述,从体系物理化学性质、电极过程机理、模拟计算等几个方面做了简要的总结和分析,以期对重稀土合金材料的制备研究提供有益的帮助.      

Alloying Elements in High Speed Steels

Ｈｉｇｈｓｐｅｅｄｓｔｅｅｌｓａｒｅｓｔｉｌｌｄｏｍｉｎａｔｉｎｇｃｕｔｔｉｎｇｔｏｏｌｍａｔｅｒｉａｌｓ,ｗｈｉｃｈｗｏｕｌｄｎｏｔｂｅｃｈａｎｇｅｄｉｎｔｈｅｎｅａｒｆｕｔｕｒｅ,ａｌｔｈｏｕｇｈｏｔｈｅｒｔｙｐｅｓｏｆｔｏｏｌｍａｔｅｒｉａｌｓ,ｓｕｃｈａｓｃｅｍｅｎｔｅｄｃａｒｂｉｄｅｓ,ｄｉａｍｏｎｄｓ,ｃｅｒａｍｉｃｍａ－ｔｅｒｉａｌｓａｎｄｃｕｂｉｃｂｏｒｏｎｎｉｔｒｉｄｅ,ｈａｖｅｂｅｅｎｒａｐｉｄｌｙｄｅｖｅｌｏｐｅｄ,ｐａｒｔｌｙｄｕｅｔｏｃｏｍｐｌｅｍｅｎｔａｒｙｏｆａｌｌ…