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在相同的制备工艺(压制、烧结、旋锻、拉拔)下,采用碳、氧、铁、镍元素含量不同的钼粉分别制备出两种φ0.1 8 mm的钼丝,对其成形过程和成品的显微组织和力学性能进行分析对比。结果表明,杂质元素含量降低,将显著净化晶界和窄化晶界,进而有助于提高钼金属的塑性和成形性;当氧含量由2 100 mg/kg降低到580 mg/kg时,钼丝的旋锻成品率提高57.2%;当铁、镍含量降低时,成品钼丝的室温延伸率提高0.51%。 相似文献
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激活后发射良好的Mo-La2O3阴极表层含有大量镧,原子浓度比约为(稍大于)10%;发射衰减的阴极表层中镧含量减少,未激活的原始阴极丝表层中镧更少。对不同状态阴极中氧含量及其变化的比较,以及碳、钼峰分析认为:发射良好阴极中镧的活性程度较大,即超额镧的存在是影响阴极工作性能的主要因素;衰减后阴极中镧的总量蝇不小,但镧的活性显著降低是阴极发射不好的主要原因。 相似文献
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实验研究了变形态Mo-La合金丝的显微组织和力学性能对La含量的敏感性.实验结果表明,随着La含量的增加,变形态Mo-La合金丝的显微组织和力学性能的变化不大.这与退火态钼合金丝的强韧化效果随La含量变化而变化的规律不同.这一现象是La元素在钼合金丝中的赋存形式及其转化过程的时序性特征所致.Mo-La合金丝中,晶粒细化和位错钉扎的效果取决于La2O3颗粒的数量及其在钼基体中的弥散度.XRD衍射谱表明,在固-液掺杂MoO2还原制得的Mo-La合金粉末中,La元素并不是以La2O3,而是以La2Mo2O7的形式存在.La2O3颗粒是在Mo-La丝的整个工艺过程中,通过La3+离子与游离态氧原子结合,或La2Mo2O7分解的途径而逐步形成的.变形态Mo-La合金丝的制备过程不足以使La3+离子全部转变为La2O3,导致La2O3颗粒的生成过程滞后于制备过程,因此La含量对Mo-La合金丝的力学性能和显微组织的影响趋势不甚明显. 相似文献
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Yan Jianhui Zhang Houan Tang Siwen Li Yimin 《中国稀土学报(英文版)》2006,24(5):548-548
The oxidation behavior of 0. 8% La2O3- Mo5Si3/MoSi2 composites at 1200℃ in air was investigated. The results reveal that the oxidation resistance of the material with 0. 8% La2O3 and Mo5Si3 is impaired. The oxidation resistance is decreased with increasing Mo5Si3 content. The mass loss follows a linear law in the initial oxidation. With oxidation time prolonging, a continuous and dense oxidation scale prevents oxygen from diffusing increasing when and leads to mass change a Mo5Si3 content is less than 30%. However, the composite shows "PEST" with the addition of 40% Mo5Si3. With increasing Mo5Si3 content, the oxidation resistance of 0.8% La2O3- Mo5Si3/MoSi2 decreases. This attributes to the poor oxidation resistance of M05Si3 and the relative density decreasing of 0. 8% La2O3-Mo5Si3/MoSi2 composite. 相似文献
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采用添加微量La2O3的方法,提高氧化锌压敏阀片的电位梯度,使之具有优良的综合性能。同时研究了数量La2O3添加剂对氧化锌压敏电阻片的压敏电位梯度的影响,并通过SEM测试手段对其微观组织结构进行了分析研究,从理论上探讨了La2O3影响氧化锌压敏阀片压敏电位梯度与组织的机理。研究结果表明,在0-0.08mol%分成范围内,随着La2O3含量的增加,氧化锌压敏阀片的压敏电位梯度明显提高;当La2O3含量超过0.08mol%时,随其含量的增加,氧化锌压敏阀片的压敏电位梯度又呈降低趋势。其原因是La2O3加入到氧化锌压敏阀片中,La主要以固溶的形态分布于ZhO的晶内和晶界处,使ZnO晶体的自由电子浓度增大,进而使填隙锌离子Zni的总浓度下降,因此填隙锌离子的传质能力下降,抑制了ZnO晶粒的生长、因而晶粒尺寸随La2O3的添加量下降,压敏电位梯度显著提高。 相似文献
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The substrate molybdenum doped with La2O3, Y2O3 cathode material was made by the powder metallurgy method. The secondary emission coefficients of the materials were tested. The experimental results show that Mo cathodes doped with La2O3, Y2O3 have good secondary emission properties. When the cathodes are activated, the maximal secondary emission coefficients of these cathodes are higher than 2.0 and can meet the practical requirement. The distribution of the rare earth in the interior and at surface of this kind of cathode material before and after emission was studied using Scanning Electronic Microscopic (SEM) and X-Ray Photoelectron Spectrum(XPS). The analysis results show that the rare earth is easy to gather at grain boundaries and the relevant concentration of rare earth on the surface after emission is obviously greater than that before emission. 相似文献
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采用粉末冶金方法制备含Y2O3的稀土钼合金,利用金相显微镜、扫描电子显微镜(SEM)、X射线衍射(XRD)、能谱分析(EDS)等手段对钼合金的断裂特征和组织结构进行对比分析,研究稀土氧化物Y2O3含量对钼合金组织和性能的影响.研究表明:添加Y2O3能细化晶粒、改善钼合金的晶粒均匀性和致密度、提高钼合金的性能:拉伸强度和屈服强度随Y2O3含量的增加呈现先增高后降低的趋势,在Y2O3含量为1%时,抗拉强度达511.43MPa,屈服强度456.99MPa,分别是纯钼材料的1.31倍和1.57倍,综合力学性能最佳;在烧结坯中,Y2O3颗粒分布均匀,主要以球形和等轴状形式存在于晶界上. 相似文献
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The effect of copper and molybdenum additions on the microstructure of particles produced by the atomization of an iron-carbon melt by an air-water jet using a new atomizer unit has been studied. The application of air-water atomization instead of water atomization is shown to intensify the solidification of particles with a fine microstructure. The introduction of molybdenum (up to 0.6 wt %) into a melt refines the structural constituents of the granules and decreases the fraction of the retained austenite, and the introduction of copper (up to 0.8 wt %) leads to the opposite results. The addition of copper (up to 0.6 wt %) and molybdenum (up to 0.6 wt %) to a melt results in a homogeneous microstructure consisting of fine acicular martensite and fine molybdenum carbides. Low-temperature vacuum tempering at 350°C for 1 h leads to insignificant decarburization of the martensite and the precipitation hardening of the base metal due to copper alloying. The microstructure of a steel alloyed by molybdenum and copper provides an increase in the wear resistance of the steel shot by a factor of 1.5–2 and high quality of the shot (close to the best foreign analogs). 相似文献
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Effect of La2O3 on granular bainite microstructure and wear resistance of hardfacing layer metal 总被引:1,自引:0,他引:1
The purpose of this work was to investigate the effect of La2 O3 on the granular bainite microstructure and wear resistance of hardfacing layer metal. The hardfacing layer metals with different contents of La2 O3 were prepared. The microstructures of the hardfacing layer metals were observed by field emission scanning electron microscopy(FESEM) and transmission electron microscopy(TEM). The hardness and wear resistance of the hardfacing layer metals were measured respectively. The results indicated that with the increasing content of La2 O3, the amount of granular bainite increased, while that of martensite decreased and that of retained austenite did not change obviously. When the content of La2 O3 was 2.55 wt.%, the volume fraction of the granular bainite in the hardfacing layer metal was 73.2%. Meanwhile, the wear resistance of the hardfacing layer metal was the largest, which was 12100 min/g. The mismatch between the face(100) of LaAlO3 and the face(100) of δ-Fe was 7.1%. Therefore, LaAlO3 could act as moderate effective heterogeneous nuclei of δ-Fe and the granular bainite could be refined. 相似文献
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采用熔盐电解法研究了La2O3电脱氧反应过程。由电位阶越实验及取样电流电位分析和对电解产物进行X衍射分析表明La2O3的电脱氧反应是可以进行的,La2O3得电子还原为低价脱氧产物LaO,接着LaO作为中间产物与阳极气体Cl结合生成氯氧镧。 相似文献
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复合添加Zr、Cr和La对铝再结晶温度的提高作用 总被引:1,自引:1,他引:0
以99.99%高纯铝为原料,以中间合金形式复合添加zr、cr和La,采用铸锭冶金法制备铝合金。通过对合金的组织结构观察和分析以及力学性能测试,研究复合添加zr、Cr和La对铝再结晶温度的提高作用。结果表明:在铝中同时添加0.1%Cr和0.28%La(质量分数,%,下同),可使铝的再结晶起始温度提高约30℃,铝的再结晶得到抑制;复合添加0.09%Zr、0.1%Cr和0.14%La,铝的再结晶起始温度提高了约30℃,终了温度提高约60℃,铝的再结晶及晶粒长大现象得到显著的抑制。与同时添加Cr和La相比,复合添加Zr、Cr和La对铝的强化作用更大。 相似文献
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采用热压工艺制备了不同Si3N4(p)和SiC(w)体积含量的MoSi2基复合材料,通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)、维氏硬度计、电子万能材料试验机等研究了复合材料的显微组织、硬度、断裂韧度和抗弯强度,并对其强韧化机理进行了初步探讨。结果表明,复合材料结构致密,强化相与MoSi2之间没有新相生成,力学性能较纯MoSi2得到大幅度提高,其中MoSi2-20%Si3N4(p)-20%SiC(w)复合材料具有最好的抗弯强度和断裂韧度,分别为427MPa和10.4MPa.m1/2。复合材料的强化机制为细晶强化和弥散强化,韧化机制为细晶韧化和裂纹偏转与分支韧化。 相似文献