共查询到19条相似文献,搜索用时 156 毫秒
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刘敏 《原子与分子物理学报》2016,33(1)
未经均匀化热处理的纯三元及含Zr, Ga元素的SC合金铸片经优化的HDDR工艺处理都可以制备各向异性NdFeB磁粉。这表明:元素的添加及SC铸片是否进行了均匀化热处理都不是HDDR磁粉各向异性形成的必要条件。磁粉各向异性形成的关键因素在于HDDR工艺的调节,即适当地加快歧化反应过程,减缓脱氢再结合过程以及控制脱氢再结合时的合适氢气压强均有利于磁粉各向异性的形成。本文将为制备低成本高各向异性磁粉提供重要的指导。 相似文献
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本文根据氢化/歧化/脱氢/重组(HDDR)Nd-Fe-B 磁粉晶粒边界微结构的特点,建立了缺陷区内的磁晶各向异性常数K1´及交换积分常数A1´的双变量连续变化模型,研究了晶粒间界相厚度d及晶粒表面结构缺陷厚度r0对磁体矫顽力的影响。结果表明:晶粒表面各向异性常数K1(0)、交换积分常数A1(0)及r0取不同值时,磁体的矫顽力Hc均随d增加而增大。K1(0)和A1(0)取确定值时,相同的d值对应的Hc随r0的增大而上升。r0和d取确定值时,Hc随K1(0)或A1(0)的减小而增大。当d 为1nm,r0 在 (2~5) nm范围内,A1(0)和K1(0)的值分别在A1和K1值的(0.6~0.7)范围内变动时,计算的矫顽力与实验值符合得很好。 相似文献
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本文根据氢化/歧化/脱氢/重组(HDDR)Nd-Fe-B 磁粉晶粒边界微结构的特点,建立了缺陷区内的磁晶各向异性常数K1´及交换积分常数A1´的双变量连续变化模型,研究了晶粒间界相厚度d及晶粒表面结构缺陷厚度r0对磁体矫顽力的影响。结果表明:晶粒表面各向异性常数K1(0)、交换积分常数A1(0)及r0取不同值时,磁体的矫顽力Hc均随d增加而增大。K1(0)和A1(0)取确定值时,相同的d值对应的Hc随r0的增大而上升。r0和d取确定值时,Hc随K1(0)或A1(0)的减小而增大。当d 为1nm,r0 在 (2~5) nm范围内,A1(0)和K1(0)的值分别在A1和K1值的(0.6~0.7)范围内变动时,计算的矫顽力与实验值符合得很好。 相似文献
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中国科学技术大学磁学教研室有关同志为研制高密度记录用磁粉,从改进国内磁粉生产工艺着手,参考国外有关资料[1-4],并结合我国具体情况,于1979年下半年研制出包附SiO2的细微针状rFe2O3磁粉. 该磁粉研制的工艺特点是采用强碱法,在比常规反应温度和浓度均低的条件下制备铁黄(a-Fe 相似文献
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添加微量元素Dy和Co后可使HDDR工艺制备的各向同性NdDyFeCoB粘结磁体的温度特性、磁性能以及微晶结构显著改善,从而得到一种具有实用价值的低温度系数、高内禀矫顽力粘结磁体.结果表明:添加适量的Dy和Co可使25—80℃时的磁通可逆温度系数α在-0043%℃左右,25—155℃时的磁通可逆温度系数α=-0056%℃;经155℃老化处理12h不可逆损失hirr为35%;最高内禀矫顽力Hci>1600kAm-1时,最大磁能积(BH)max仍可获得一个较好值.
关键词:
HDDR工艺
温度特性
微结构
内禀矫顽力 相似文献
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火花源原子发射光谱原位统计分布分析技术(OPA)是近十几年发展起来的一种大尺度金属截面的高通量成分分布分析技术,具有分析速度快、多元素信号同时定位采集、统计解析信息量大等独特优势,已被广泛应用于中低合金钢铸坯中的成分分布分析。采用火花源OPA技术对铸&锻变形FGH96高温合金航空发动机涡轮盘纵剖面中的主要合金元素Al,Cr,Co,Ti,W,Mo和Nb进行了成分分布分析,并通过适宜的校准曲线的拟合实现了七种合金元素的定量统计解析。采用直读光谱仪对纵剖面轮毂至轮缘的不同部位进行了定点分析,两种方法具有较好的一致性。结果表明,经过新的铸&锻工艺生产的变形FGH96涡轮盘中除了含量较低的Nb元素外,大部分元素的统计偏析度都小于5%。由于涡轮盘不同部位冷却方式的差异,导致轮毂和轮缘上某些元素分布的差异,其中Ti,Nb等碳化物形成元素在轮缘处存在一定的偏析,含量有所升高,而W,Mo和Co则在轮中部分布较不均匀,采用扫描电镜结合能谱分析的方法也观察到了轮缘处了大颗粒的Ti和Nb的碳化物的存在,进一步证实了涡轮盘边缘Ti和Nb偏析的存在。大尺度涡轮盘的元素成分分布分析结果对于FGH96合金涡轮盘新型铸&锻变形工艺的改进和性能提高具有重要的指导作用。 相似文献
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《中国科学:物理学 力学 天文学(英文版)》2010,(9)
Effects of the wheel speeds v and disproportionation time during the SC-HDDR process on the properties of Nd-Fe-B magnetic powders are investigated.It is found that the remanence Br,coercivity Hcj and energy products(BH)max of magnetic powders all first increase to the maximum at v=3 m/s,and then decrease with enhancing v.This is attributed to the fact that the SC alloy flakes prepared by the wheel speed of 3 m/s display the optimized microstructure.This optimized SC alloy flakes without homogenizing treatment which carried out a short duration disproportionation treatment can prepare the evidently anisotropic powders.With prolonging disproportionation time,the alignment degree of anisotropy of magnetic powders gradually decreases.This is due to the fact that a short duration disproportionation reaction is beneficial to the disproportionated microstructure displaying the lamella crystals,and the lamella disproportionated microstructure is helpful to the formation of anisotropy.Our results confirm that the anisotropic HDDR Nd-Fe-B magnetic powders prepared directly from the SC alloy flakes without homogenizing treatment can be obtained. 相似文献
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《Journal of magnetism and magnetic materials》2004,269(3):293-301
In order to examine the possibility of applying the HDDR process to segregated master ingots, Nd–Fe–B system HDDR powders were made from ingots with different levels of homogeneity, and their structures and magnetic properties were evaluated in detail. HDDR powders made from segregated as-cast ingots displayed anisotropy and large coercivity. They had a nearly homogeneous Nd2Fe14B phase, although some large areas with α-Fe and Nd-rich regions of 30 μm in size were present after the HD process. With increasing in the homogeneity level of the master ingots, the anisotropy of HDDR-processed powders decreased and their coercivity increased. In addition, an intermediate Ar treatment was applied between the HD and DR processes to improve the magnetic properties. As a result, the effect of the IA treatment was clearly confirmed, and good magnetic properties of Br=1.23 T, HcJ=848 kA/m and (BH)max=238 kJ/m3 were obtained. 相似文献
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For the HDDR Nd13.5Fe79.5B7 magnetic powders, effects of disproportionation time and hydrogen pressure on the anisotropy were studied during the slow desorption stage. Studies showed that shorter disproportionation times caused the magnetic powders displaying higher anisotropy. With increasing disproportionation times, the degree of crystallographic alignment decreased. This in turn caused a drop in remanence and anisotropic character. Longer disporportionation times have also been correlated to a change in disproportionated microstructure from lamella to columnar. XRD (X-Ray Diffraction) studies showed that except NdH2,α-Fe and Fe2B, no other phases were included in the disproportionation mixture. This elucidated that the strong anisotropy is only related to a lamella disproportionation microstructure, which corresponds to a short disproportionation times. The lamella disproportionation microstructure may remain or inherit the alignment of original Nd2Fe14B grain, and may also be related to the alignment of the newly formed Nd2Fe14B grain. Thus, the anisotropic formation mechanism of ternary magnetic powders accords with “anisotropy-mediating phase” model. If the disproportionation mixture were carried out an optimum hydrogen pressure treatment during the HDDR process, the degree of crystallographic alignment can be further enhanced. 相似文献
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《中国物理 B》2015,(9)
The influence of the RE-rich phase distribution in the precursor alloys on the anisotropy of the hydrogenation disproportionation desorption recombination(HDDR) processed powders is investigated. The homogenized ingot alloy and the as-cast strip casting(SC) alloy with a uniform RE-rich grain boundary phase lead to high anisotropy of the refined powders,acquiring degrees of alignment(DOA) of 0.62 and 0.54, respectively. The RE-rich phase aggregation results in a deteriorated DOA of the powders due to the drastic disproportionation rate, while a thin and uniform RE-rich phase distribution is beneficial for DOA. A reaction model of the initial particle microstructure is proposed for optimizing the HDDR powder anisotropy. 相似文献
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Jingzhi Han Shunquan Liu Changsheng Wang Haiying Chen Honglin Du Yingchang Yang 《Journal of magnetism and magnetic materials》2009,321(9):1331-1334
Effects of the conventional hydrogenation disproportionation desorption recombination (HDDR) process and the additions of Co and Zr on anisotropy of HDDR PrFeB-type magnetic materials are investigated. The results show that the degree of anisotropy in conventional HDDR Pr13Fe80B7 materials decreases monotonically with the prolonged disproportionation time, and short disproportionation time is helpful for preparing highly anisotropic Pr13Fe80B7 material. However, it is notable that the degree of anisotropy in conventional HDDR Pr13Fe80B7 materials is significantly smaller than that in solid-HDDR Pr13Fe80B7 materials with the same disproportionation time. At the same time, it is found that the addition of Co and Zr may make HDDR Pr-Fe-B materials that have higher anisotropy compared with HDDR pure ternary Pr13Fe80B7 materials under the same HDDR process, but their degree of anisotropy will also decrease monotonically with the prolonged disproportionation time, and will be close to zero when the disproportionation time is greater than 20 h. Based on this, the origin of anisotropy is discussed by X-ray diffraction (XRD) investigations for the disproportionated products of the above alloys. The results show that the origin of anisotropy in HDDR Pr-Fe-B materials with the addition of Co or Zr may differ from that in HDDR pure Pr13Fe80B7 materials, and the former maybe from the residual “Pr2(Fe,Co,Zr)14B” nucleus while the latter is not. Finally, it is also found that HDDR Pr-Fe-B materials with Co or Zr can obtain high-magnetic properties even if the high-desorption temperature is used, and this shows the addition of Co and Zr may make HDDR Pr-Fe-B materials that have a larger process temperature range. 相似文献
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Nitrided Sm2Fe17-based materials possess excellent intrinsic magnetic properties. In this study, we investigate two compositions, Sm13.7Fe86.3 and Sm13.8Fe82.2Ta4.0. The stoichiometry of each phase was determined and the SmFeTa material was found to include Ta3Fe7, in addition to the Sm2Fe17, SmFe2, and SmFe3 phases observed in the SmFe alloy, but without the α-iron dendrites characteristic of the binary material. SEM and TEM studies revealed that in the cast structure, approximately 2.0% Ta is initially dissolved in the Sm2(FeTa)17 phase; however, HDDR processing causes the formation of Ta-based precipitates, leaving a 2: 17 phase with much less dissolved Ta. The HDDR process, with subsequent nitrogenation, was used to prepare coercive powders. The coercivities of these powders were found to be very dependent on the HDDR conditions and Ta addition. The highest coercivity achieved was 1280 kA/m for the composition with Ta. 相似文献
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Jingzhi Han Changsheng WangHonglin Du Haiying ChenYingchang Yang 《Journal of magnetism and magnetic materials》2008
Effects of such additives as Co, Zr, Nb or Ga on hydrogen absorption and desorption characteristics of Nd(Fe,Mo)12 alloys are investigated. It is found that Zr or Nb addition increases the disproportionation temperature of Nd(Fe,Mo)12 alloys, and Co or Ga addition decreases the recombined temperature of its disproportionated products. This shows that Zr or Nb addition retards the disproportionation, while Co or Ga addition is effective for improving the recombination, which is similar to the effects of the additives on the hydrogen absorption and desorption characteristics of Nd2Fe14B alloys. However, according to X-ray diffraction (XRD) investigations for the magnetic-oriented samples, the final hydrogenation disproportiontation desorption recombination (HDDR) NdFe10.5−XMXMo1.5 (M=Co, Zr, Nb or Ga) products are isotropic. The effects of additives on hydrogen absorption and desorption characteristics of Nd2Fe14B and Nd(Fe,Mo)12 alloys are very similar, but the magnetic anisotropy of the final two HDDR products are different. In order to investigate this, similarities and differences of the two alloy systems and their corresponding HDDR phenomena are further studied. The results show that the formation of anisotropic powders may be related to the disproportionated products and crystal growth direction of the Nd2Fe14B and Nd(Fe,Mo)12 system. 相似文献
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C. E. Rodrí guez Torres F. D. Saccone F. H. S nchez 《Physica B: Condensed Matter》2002,320(1-4):308-311
Remanence, coercivity and maximum energy product (BH)max of Nd16Fe76−xHfxB8 (x=0, 0.1, 0.2) magnets processed under different hydrogenation-disproportionation-desorption-recombination (HDDR) conditions, were studied. Vibrating sample magnetometry results showed that Hf-doped materials develop an important degree of anisotropy, especially for the case of solid-HDDR treatments at 800°C and 850°C, with the largest effect at 850°C. Maximum values of remanence and coercivity were observed for Hf-added samples S-HD at 850°C, and 900°C, respectively. The highest (BH)max value was also observed in S-HD 900°C Hf-added samples. These results are discussed in terms of the expected microstructure of the intermediate HD and final HDDR processed powders. 相似文献
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Lubricants generally are used in the milling process of silver powders to flakes to nullify the forces of welding and thereby inhibit agglomeration. The study was carried out to fully understand the interaction of silver flakes with a commonly used lubricant, oleic acid. Silver flakes were prepared by ball milling of precipitated fine silver powders with oleic acid in amounts about 1.0 wt.%. Thermal properties of lubricated silver flakes and silver flakes treated by several chemicals were studied; the efficiency of the lubricant removal was estimated by the DSC exothermic peak in air. It was found that a mixture of solvent and diluted sulfuric acid can fully remove the lubricant on the surface of silver flakes. The morphology of silver flakes before and after treatment by a mixture of alcohol and diluted sulfuric was observed by scanning electron microscopy; the lubricant removal was also confirmed. 相似文献