HDDR技术制备高性能稀土永磁磁粉研究

利用HDDR技术研究了NdFeCoBZrGa合金的磁性能.研究了HD处理温度对合金磁粉磁性能和DOA的影响规律;研究了DR处理温度对合金磁粉磁性能和DOA的影响规律;研究了合金成分对合金磁粉磁性能和DOA的影响规律.结果表明通过适当工艺的调整,成功制备出高性能、高各向异性粘结磁体磁粉.对于成分为Nd13FgbalCo17B6 5Zr01Ga10的合金,其磁性能达到iHc=817.6kA/m,Br=1.18T,(BH)max=244kJ/m3,其取向度DOA达到0.56.     

改进HDDR工艺制备NdFeCoZrBGa各向异性磁粉

HDDR(氢化-歧化-脱氢-重组)工艺是一种用于生产各向异性Nd2Fe14B基磁粉的特殊方法。本文主要研究了添加微量含金元素Ga、采用改进HDDR工艺(即在HD处理及高真空脱氢处理之间加上低真空脱氢处理)对Nd11.2Fe66.5-xCo15.4B6.8Zr0.1Gax(x=0、0．1、0．3、0．5、1．0)合金磁性能的影响规律。结果表明．改进HDDR工艺对于提高磁粉性能,细化主相晶粒尺寸非常有效。微量合金元素Ga的添加可显著地改变材料歧化分解的特征,同时可提高磁粉的磁性能。由改进HDDR工艺制得磁粉主相晶粒尺寸明显小于由传统HDDR工艺制得磁粉主相晶粒尺寸。     

Sm3(Fe,Co,Ti)29合金HD和HDDR处理研究

深入研究了合金Sm3Fe18.5Co9Ti1.5的HD和HDDR处理过程.HD过程分别于350、400和450℃处理4h;HDDR过程于800℃处理2h.试验发现HD和HDDR法均可有效的对合金进行破碎处理,HDDR法由于其形核长大机制可有效的用于制备纳米晶复合材料;350℃时HD法可以有效的进行,随着温度的升高试样发生分解反应.给出了HD及HDDR处理后合金所表现的典型形貌.     

Sm2Fe17和Sm10.5Fe88.5Zr1.0的氮化行为

通过真空电弧炉制备了Sm2Fe17和Sm10.5Fe88．5Zr1．0母合金，铸态Sm2Fe17先经均匀化处理后再氮化．而Sm10.5Fe88．5Zr1．0则不经均匀化退火而直接在高纯氮气中氮化。运用扫描电子显微镜和X射线衍射技术对其氮化行为进行了研究。薄片扩散实验表明氮在Sm2Fe17中的扩散要比在Sm10.5Fe88．5Zr1．0中的扩散快。运用Fick第二定律通过理论计算得出直径为20μm的Sm2Fe17合金和Sm10.5Fe88．5Zr1.0合金球形粉末粒子，实现充分氮化的时间为10h和16h。实际粉末实现完全氮化的时间要比理论计算的时间少。这和粒径分布、颗粒表面状态、氮化过程产生的微裂纹以及实际条件和理想条件的差异有关。对于直径为20μm的粉末，氮化时间为6h时氮化已基本完成，氮化时间过长．Sm2Fe17Nx会发生分解。     

热处理对Fe69.07Ni29.25Mn0.615Si0.50C0.50磁温度补偿合金热磁性能和微观结构的影响

研究了热处理工艺对Fe69．07Ni29．25Mn0．615Si0．50C0.50磁温度补偿合金的组织结构和热磁性能的影响,采用X射线衍射仪及金相显微镜分析其相结构和组织形貌。结果表明热处理工艺对磁温度补偿合金的热磁性能有较大影响;随热处理温度、时间增加,合金由a、γ双相结构变为γ单相结构;具有优良热磁性能的磁温度补偿合金的结构组织应为γ单相面心立方结构,大的晶粒尺寸、少的内部缺陷和低的内应力。     

HDDR处理的Sm2Fe16.5Ti0.5合金的结构与氮化

采用HDDR及氮化工艺制备了Sm2Fe16.5Ti0.5Ny粉末.铸态Sm2Fe16.5Ti0.5合金存在择优取向,Sm2(Fe,Ti)17主相的214衍射峰增强.均匀化退火后,只有约0.6%的α-Fe(Ti)相与主相Sm2(Fe,Ti)17共存.经不同循环的HDDR工艺处理后,物相组成不发生变化,但α-Fe(Ti)相含量增加.HDDR工艺有助于获得细晶结构,提高磁粉的矫顽力.HDDR处理的合金的氮化由初期的Sm-Fe-Ti合金与氮快速反应阶段及后期氮在合金中的均匀化扩散阶段组成.随着氮化时间的延长,富铁相含量增加.氮化物中Sm2(Fe,Ti)17Ny主相的晶格膨胀行为由HDDR与氮化工艺共同决定.在500℃氮化2h后,796kA/m最大外场下得到的最大矫顽力为164.9kA/m,氮化12h时后得到最大剩磁45.7Am2/kg.     

歧化氢压对Nd12.5Fe80.4-xCoxGa0.5Zr0.1B6.5各向异性HDDR磁粉性能的影响

主要研究了d-HDDR工艺及添加合金元素Co对Nd12.5Fe80.4-xCoxGa0.5Zr0.1B6.5(x=0、4、8、12、15)合金磁性能的影响规律.结果表明,氢压是HDDR磁粉吸氢歧化产生磁各向异性的重要敏感因素,0.025MPa的歧化氢压对提高磁粉的各向异性具有最好的效果,磁能积达到:Br=1.252T,jHc=768.7kA/m,(BH)max=253.4kJ/m3,DOA=0.58.(合金元素Co的添加有益于HDDR磁粉磁性能改善,在0～15%(原子分数),随着Co含量增加d-HDDR磁粉的磁能积逐渐增大.     

含Nb和Sm的AlNiCo合金

在AlNiCo合金中加入适量的Nb和Sm,获得了较高的综合磁性能。含量为0．5-0．7％Nb的AlNiCo5合金磁性能可稳定在Hc≥700e,Br≥13000G,(BH)max≥7MGOe；含量为0．6％Nb的合金,获得最佳的磁能积为8．4MGOe。含量为0．7%Nb,0．1-0．5％Sm的合金磁性能可达到：Hc≥8000e,Br≥13000G,(BH)max≥7．5MGOe；含量为0．7％Nb,0．5Sm的合金获得最佳的磁能积为8．45MGOe。含量为0．5-1％Nb的AlNiCo8合金,在磁场中连续控速冷却处理和回火后,磁性能可达到：Hc≥1400Oe,Br≥10500G,(BH)max≥9MGOe,得到最佳的磁能积为11．6MGOe；经等温热处理和回火后,磁性能可达到：Hc≥1400Oe,Br≥10500G,(BH)max≥10MGOe,获得最佳的磁能积为12．6MGOe。在AlNiCo合金中加入合金元素Nb,使α→α y相的临界冷却速度降低；α→α1 α2相转变的温度范围下降和加宽；磁性能对冷却速度和等温温度的敏感性降低,方便了大断面磁钢的热处理。含量为0．7％Nb的AlNiCo5合金以1．5-3．3℃／sec由1300℃冷却至900℃,在磁场中以0．2-0．35℃／sec由900℃至600-700℃进行热磁处理。含量为1%Nb的AlNiCo8合金,可和AlNiCo5合金一样,采用在磁场中连续控速冷却热处理工艺,以2-5℃／sec由1250℃冷却至900℃；在磁场中以0．2-0．35℃／sec由900℃冷却至600-700℃,：这样更利于大断面、异型、多极AlNiCo8合金的热处理。     

Nd13Fe80.1-xTixB6.5Zr0.1Cu0.3永磁合金磁性能研究

HDDR(氢化-歧化-脱氢-再结合)工艺是制备各向异性Nd2Fe14B基磁粉的有效方法.主要研究了改进的d-HDDR工艺及添加合金元素Ti对Nd13Fe80.1-xTixB6.5Zr0.1Cu0.3(x=0、1.0、2.0)合金磁性能的影响规律.结果表明,d-HDDR工艺中吸氢氢压和歧化时间是促使材料产生磁各向异性的#合金经d-HDDR工艺处理,其最佳磁性能为:Br=1.39T;iHc=1006kA/m;(BH)max=169.66kJ/m3;DOA=0.797.关键;合金元素Ti使NdFeB合金矫顽力显著提高,其作用主要体现在两方面:一方面是在晶界间形成低熔物,抑制晶粒长大、细化晶粒,改善富Nd相的组织结构,使富Nd相沿边界更加均匀地分布;另外,Ti元素使Nd2Fe14B晶界平直而清晰,主相晶粒表面各向异性提高,反磁化畴难以形核,从而使矫顽力提高,其最佳添加量为1.0%(原子分数).成分为Nd13Fe79.1Ti1.0B6.5Zr0.1Cu0.3 的2#合金经d-HDDR工艺处理,其最佳磁性能为:"Br=1.39T;iHc=1006kA/m;(BH)max=169.66kJ/m3;DOA=0.797.     

硼元素对Fe-6.5%(质量分数)Si合金力学性能影响的试验研究

含Si约6．5％(质量分数)的Fe-Si合金具有优异的软磁性能．但由于其室温脆性差而难以通过常规的冷轧工艺加工成薄板。本文研究了微合金化元素-硼对铸态Fe-6．5%(质量分教)Si合金组织和性能的影响．以及该合金薄板在不同温度下拉伸的力学性能，并观察了拉伸断口形貌，结果表明．硼元素的添加使得该铸态合金晶粒细化．从而提高了该合金的塑性。Fe-6．5％(质量分数)Si合金薄板在不同温度下的拉伸结果表明．室温延伸率达到6．4％．500℃延伸率速最大值(32．96％)．明显高于600℃时的延伸率，原因是600℃处于B2和DO3两相区．在温度600℃下发生了DO3相到B2相的转变．使得B2相有所增加。B2相的增加降低了Fe-6．5%(质量分数)Si合金的塑性。     

Influence of nickel addition on magnetic and electro-mechanical behaviour of permalloys

Magnetic and electro-mechanical investigations have been carried out in two Ni-Fe permalloys under hydrogen atmosphere by varying annealing temperature. These alloys have been characterized for various magnetic parameters like peak permeability, coercivity and core loss under changed annealing profile conditions. The magnetic properties of Ni-rich (Ni ∼ 82%) alloy at 100 Hz were found to be better than the low Ni (Ni ∼47%) alloy. The alloys were tested for watch movement and found that the battery life of the watch movement improved by 38% using Ni-rich permalloy.     

Study on the microstructures and the magnetic properties of precipitates in a Cu75-Fe5-Ni20 alloy

The microstructural evolutions of precipitates formed in a Cu75-Fe5-Ni20 alloy on isothermal annealing at 873 K and 1073 K have been investigated by means of transmission electron microscopy (TEM). Nano-scale magnetic particles were formed randomly in the Cu-rich matrix after receiving a short annealing due to phase decomposition in the alloy. With increasing the isothermal annealing time, however, the striking features that two or more nano-scale particles with a cubic shape and a rod shape were aligned linearly along (100) directions were observed on isothermal annealing at 873 K and 1073 K, respectively. To investigate electro-magnetic properties of precipitates in a Cu-Fe-Ni alloy, the superconducting quantum interference device (SQUID) magnetometer and physical property measurement system (PPMS) were also complemented. The present study revealed significant influences that the magnetic properties of the specimens were closely related to the microstructures in the Cu-Fe-Ni alloy, which microstructures significantly depend on the isothermal annealing temperature.     

Development of cost-effective nanocrystalline multi-component(Ce,La,Y)-Fe-B permanent magnetic alloys containing no critical rare earth elements of Dy,Tb,Pr and Nd

Here we first report the fully abundant rare earth(RE)-based nanocrystalline multi-component(Ce,La,Y)-Fe-B alloys containing no critical RE elements of Nd,Pr,Dy,and Tb by melt-spinning technique.The roles of La and Y substitutions for Ce have been fully understood.La plays a positive role on both thermal stability and room-temperature(RT)magnetic properties.The enhanced coercivity Hcj by partial substitution of La is attributed to the increases of anisotropy field HA and the formation of continuously distributed grain boundaries resulting from the suppression of CeFe2 phase.Although Y substitution is not benefit for Hcj,both remanent polarization Jr and thermal stability have been effectively improved since Y2Fe14B shows relatively high saturation magnetization Ms and a positive temperature coefficient of HA over a certain temperature range.In addition,RE element segregation has been confirmed,La prefers to enter into the grain boundaries than Ce and Y prefers to remain in the 2∶14∶1 phase.Based on these understanding,a series of melt-spun(Ce,La,Y)-Fe-B alloys have been designed.A relatively good combination of magnetic properties with maximum energy product(BH)max=7.4 MGOe,Hcj=400 kA/m,and Jr=0.63 T has been obtained in[(Ce0.8La0.2)0.7Y0.3]17Fe78B6 alloy,together with high Curie temperature(Tc=488 K)and low temperature coefficients of remanence(α=-0.255％/K)and coercivity(β=-0.246％/K).     

Soft magnetic structural alloys for elevated-temperature applications

Metallurgical efforts to develop a soft magnetic material suitable for application in the rotor of a generator or motor in advanced aerospace electric systems are reviewed. Commercial materials which have been considered include AISI 4340 steel, H-11 steel, Nivco alloy, and 15- and 18-percent Ni maraging steels. Developments described have led to several new materials with combination of good mechanical and magnetic properties at elevated temperature. Such materials include an improved maraging steel a precipitation hardenable cobalt-base alloy, a carbide strengthened Co-W alloy, dispersion-strengthened soft magnetic alloys, and unidirectionally solidified Co-Nb-Fe eutectic alloys.     

多孔Ni-Mn-Ga-Co磁性形状记忆合金的制备及磁学特性研究

首先采用球磨法制备了不同粒度的Ni-Mn-Ga-Co合金粉末,然后通过3D打印技术成功制备了泡沫结构的多孔Ni-Mn-Ga-Co磁性形状记忆合金。利用SEM、DSC和XRD等研究了合金的微观组织特征、物相结构、相变特性和相关的磁性行为。结果表明,球磨后经过分筛得到的不同粒径尺寸的合金粉末均为不规则形状。Ni-Mn-Ga-Co合金粉末在室温下为非调制四方马氏体结构,其特征峰十分明显。Ni-Mn-Ga-Co合金的DSC曲线上出现宽峰相变,添加Co元素对马氏体转变温度开始值(Ms)基本没有影响,但其居里温度(Tc)有显著的提高。采用粒径为50~100μm的合金粉末烧结制备的磁性合金,饱和磁化强度最大可达68 Am^2/kg。合金粉末粒径越小,烧结制备的多孔Ni-Mn-Ga-Co磁性形状记忆合金致密度越高。当合金粉末粒径<50μm时,致密度可达90%;当合金粉末粒径为50~100μm时,致密度仅为75%。相较于粒径较小的合金粉末,粒径较大的合金粉末制备的磁性合金磁感生应变能力更高,这是由于泡沫结构能够有效减少内部和外部的约束,从而有利于提高磁场诱导应变。     

Ce2Fe16.5Co0.5合金的磁熵变研究

在氩保护气氛中用熔炼法制备了 Ce2Fe16.5Co0.5合金,通过粉末 X射线衍射和 SQUID 磁强计研究了样品的结构和磁熵变。结果表明 Ce2Fe16.5 Co0.5合金具有菱方Th2Zn17型结构,且存在不同组分的2个相,主相Ce2(Fe,Co)17和次相 Ce(Fe,Co)7。在 242~285K宽温区出现一个磁熵变平台,从而能够满足磁Ericsson型磁致冷机的要求,这对实际磁致冷应用具有现实意义。     

Soft Magnetic Properties of Fe-5wt%Al Alloy

In this investigation, a new soft magnetic material (iron with 5 wt% aluminum) has been developed using powder metallurgy processing. The microstructure and the magnetic properties of this new P/M alloy have been characterized at both room and elevated temperatures (up to 500°C). The influence of post-sintering (after initial processing) on the porosity and magnetic properties of this material has also been examined.

Test results show that the room temperature soft magnetic properties of this alloy are comparable to other commercially available soft magnetic materials such as P/M pure Fe, Fe-Si, Fe-P, etc. Post-sintering at 1316°C resulted in significant grain growth and lower porosity with more rounded pore morphology and improved the magnetic properties. While the magnetic induction of the alloy was essentially constant from room temperature to 500°C, the coercivity of the material decreased significantly at elevated temperature. This new P/M alloy may be a suitable soft magnetic material for high temperature (up to 500°C) applications.     

Tb2Fe17-xCrx化合物的结构与磁性

通过X射线衍射及磁测量手段研究了Tb2Fe17-xCrx（x=0、0．5、1．0、1．5、2．0、3．0)化合物的结构与磁性。研究结果表明Tb2Fe17-xCrx化合物具有Th2Ni17型结构，随着Cr替代量x的增加，Tb2Fe17-xCrx化合物的单胞体积呈现非线性的减小，而晶胞参数a、c呈现复杂的变化。分析表明Tb2Fe17-xCrx化合物中存在着较强的磁一弹耦合效应。对磁性质的研究结果表明随着Cr替代量x的增加，Tb2Fe17-xCrx化合物的居里温度升高，在x=1．0时达到最大值，为539K，当Cr替代量x继续增加时，Tb2Fe17-xCrx化合物的居里温度下降。随着Cr替代量x的增加，Tb2Fe17-xCrx化合物的自发磁化强度急剧下降，分析表明在Tb2Fe17-xCrx化合物中，Cr的磁矩反平行于Fe的磁矩。     

FeCoNi-SiO2合金纳米颗粒体的制备和磁性研究

采用溶胶－凝胶法制备了FeCoNi-SiO2合金颗粒体，利用透射电子显微镜（TEM）观察了嵌在SiO2母体中的合金微粒体的形貌，利用X射线衍射（XRD）确定了样品的相结构；用振动样品磁强计（VSM）测定了样品的各种磁性参数，特别是详细研究了制备条件和合金含量对材料的磁学性质的影响，还研究了合金中的Ni含量对材料的磁学性质和合金微粒晶格常数的影响。