Effect of carbon on the coefficient of thermal expansion of as-cast Fe−30wt.%Ni−12.5wt.%Co−×C invar alloys

The segregation (distribution) of nickel and the composition of its constituents influence the low thermal expansion characteristics (Invar effect) in Fe?30 wt.% Ni?12.5wt.% Co?×C Invar alloy. The change of coefficient of the thermal expansion and magnetic properties were studied as an aspect of carbon addition causing the segregation of Ni in primary austenite of as-cast Fe?30wt.% Ni?12.5wt.% Co Invar alloy. The coefficient of thermal expansion of Fe?30 wt.% Ni?12.5 wt.% Co?×C Invar alloy showed its lowest value at 0.08 wt.% carbon, increased with increasing carbon content in the range of 0.08–1.0 wt.%C, kept constant at 1.0–2.0 wt.%C and decreased at carbon higher than 2.0 wt.%. The effective distribution of the coefficient of nickel in as-cast Fe?30 wt.% Ni?12.5 wt.% Co?×C Invar alloy increased with increasing carbon content. The volume fraction of the γ phase of Fe?30 wt.% Ni?12.5 wt.% Co?×C alloy increased with increasing carbon content. The microstructure of Fe?30 wt.% Ni?12.5 wt.% Co?×C alloy changed with the carbon content was independent of the coefficient of thermal expansion. The Curie temperature changed linearly with the carbon content and was similar to the change of the coefficient of thermal expansion. Moreover, the coefficient of thermal expansion decreased when the ratio of saturation magnetization to Curie temperature (σ_s/T_c) increased, decreasing the Curie temperature and showed a specific relationship with the magnetic properties of the Fe?30 wt.% Ni?12.5 wt.% Co?×C Invar alloy.     

YTi（Fe_（1－x）Co_x）_（11）的化学法合成及其结构、磁性能

应用共沉淀－还原扩散法成功地合成了ＹＴｉ（Ｆｅ（１－ｘ）ＣＯｘ）（１１）系列稀土永磁合金（ｘ＝０．０，０．１５，０．２５，０．５），确定了其最佳合成条件，采用ＸＲＤ研究了其晶体结构及在Ｍ１５５型振动样品磁强计上测了其居里温度和磁化强度。得出：ＹＴｉ（Ｆｅ（１－ｘ）ＣＯｘ）（１１）系列合金均具有ＴｈＭｎ（１２）型结构，其晶胞参数随Ｃｏ掺入量增大而减小；居里温度点随Ｃｏ掺入量增大而升高；比饱和磁化强度在ｘ＝０．１５处达到最大。     

Co67.5Fe4.5Ni3Si10B15非晶丝巨磁阻抗性能及其温度稳定性研究

研究了Co67.5Fe4.5Ni3Si10B15非晶丝巨磁阻抗性能及其温度特性。该非晶丝采用内圆水纺法制备,并在氮气保护下进行直流应力退火。在氮气中退火的非晶丝样品具有良好的表面光洁度以及较好的软磁性能和巨磁阻抗效应(GMI)。在激励功率6dBm、激励频率70MHz的测试条件下,磁阻抗变化率高达125%,巨磁阻抗最大灵敏度达3.92%/A·m-1。该非晶丝的巨磁阻抗性能在233～353K温度范围内具有优异的温度稳定性,为非晶丝应用于工业磁传感器等领域奠定了基础。     

金属间化物Nd(Fe_(1-x)Co_x)_(10)V_2的磁性能机制

通过X射线衍射.磁测量和M(?)ssbauer谱测定了Nd（Fe1-Cox）10V2的结构和磁性.结果表明,Nd（Fe1-xCox）10V2（x=0,0.05,0.10,0.15,0.20）化合物的晶体结构均为ThMn12型结构;随着 Co含量x的增大,晶格常数将单调减少.Co原子的替代将导致化合物各个Fe晶位上的磁超精细场值Bhf逐渐增加.Co部分取代Nd（Fe1-xCox）10V2中的Fe原子时.将择优占据8i铁晶位.取向样品NdFe10V2的热磁曲线和变温M(?)ssbauer谱研究结果表明.该化合物在T=120K条件下存在自旋重取向现象.     

Structure and magnetic properties of mechanically alloyed Tb0.2Pr0.8(Fe0.4Co0.6)1.93 and magnetostriction of its epoxy composite

The C15 Laves phase with composition Tb0.2Pr0.8(Fe0.4Co0.6)1.93 was synthesized by mechanical alloying (MA) and subsequent annealing process. The structure and magnetic properties of Tb0.2Pr0.8(Fe0.4Co0.6)1.93 were investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer, and a standard strain technique. The effect of annealing on the structure and magnetic properties was studied. The analysis of XRD shows that the high Pr-content Tb0.2Pr0.8(Fe0.4Co0.6)1.93 alloy with the single phase of MgCu2-type structure can be success-fully synthesized by MA method. The sample annealed at 450℃ is fotmd to have a coercivity of 196 kA/m at room temperature. An ep-oxy/Tb0.2Pr0.8(Fe0.4Co0.6)1.93 composite was produced by a cold isostatic pressing technique. A large magnetostriction of 400 ppm, at an ap-plied magnetic field of 800 kA/m, was found for the composite. The epoxy-bonded Tb0.2Pr0.8(Fe0.4Co0.6)1.93 composite combines a high mag-netostriction with a significant coereivity, which is a promising magnetostrictive material.     

Characteristics of permittivity and permeability spectra in range of 2-18 GHz microwave frequency for La1-xSrxMn1-yByO3 （B=Fe, Co, Ni）

Doped LaMnO3 has unusual electromagnetic properties, which makes it possible for this material to be used for absorbing microwave. LaMnO3 systems doped by Sr at site A and Fe or Co, Ni at site B were prepared by sol-gel as an microwave absorption material and their permittivity and permeability spectra were measured by microwave vector network analyzer in the frequency range of 2-18 GHz. A novel phenomenon is discovered that the complex permittivity, complex permeability and electromagnetic loss tangent have suddenly a step change at a certain frequency and the step-change frequency is relevant to content of Sr and Fe or Co, Ni. The samples show mainly dielectric loss when microwave frequency is smaller than the step-change frequency, and mainly magnetic loss when larger than that frequency. It is indicated that anti-ferromagnetic clusters in the material can absorb energy quantum of microwave electromagnetic field to change into ferromagnetic clusters because they can overcome higher energy barrier when the frequency of incident microwave reaches a certain value.     

Electrodeposited Ni,Fe,Co and Cu single and multilayer nanowire arrays on anodic aluminum oxide template

The Ni, Fe, Co and Cu single and multilayer nanowire arrays to make perpendicular magnetic recording media were fabricated with nanoporous anodic aluminum oxide (AAO) templates from Watt solution and additives by the DC electrodeposition. The results show that the diameters of Ni, Fe, Co and Cu single and multilayer nanowires in AAO templates are 40–80 nm and the lengths are about 30 μm with the aspect ratio of 350–750. The magnetic properties of the prepared nanowires are different under different electrodepositing conditions. The remanences (B_r) of Ni/Cu/Fe multilayer nanowires are lower than those of others multilayer nanowires, and coercivity (H_c) of Ni/Cu/Fe multilayer nanowires are lower than those of others multilayer nanowires. These are compatible with the required conditions of high density magnetic media devices that should have the low coercivity to easily success magnetization and high remanence to keep magnetization after removal of magnetic field.     

Magnetic, magnetocaloric and neutron diffraction studies on TbNi5−xMx (M = Co and Fe) compounds

The effect of substitution of Co and Fe for Ni in TbNi₅ on the structural, magnetic and magneto-thermal properties has been investigated. Considerable enhancement of Curie temperature is observed with Fe substitution, whereas the increase is nominal in the case of Co. Neutron diffraction measurements reveal the redistribution of moments and site preference of substitutional ions in Ni 2c and 3g sites. In TbNi₄Fe, both Ni and Fe as well as Tb are found to carry moment while in the case of TbNi₄Co, mainly Tb carries the moment. Magnetocaloric behavior has been investigated from the magnetization and the heat capacity measurements. The magnetic and magnetocaloric properties are found to be strongly correlated in these compounds.     

铁、钴、镍粘结的(W、Ti)C硬质合金的碳含量研究

分别采用铁、钴、镍作为粘结剂 ,研究了在 YT5、YT14、YT15硬质合金中出现正常组织时的碳含量范围。发现合金的正常组织含碳量范围在 Fe粘结时最窄 ,而在 Co粘结时较宽 ,Ni粘结时 C%范围最宽 ;而出现正常组织时合金的含碳量在 Ni粘结时较低 ,Co粘结时稍高 ,Fe粘结出现正常组织时合金的含碳量最高。     

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 研究了非晶丝材磁致伸缩系数的小角转动测量方法，采用小角转动法(SAMR)测量了Co69.9Si12.5B9Fe5Cr3.5Mo0.1非晶合金丝感应电压的二次谐波信号随直流偏磁场、应力及驱动电流的变化关系，通过对测量条件的优化，测量了非晶丝感生各向异性场随应力的变化关系。得到Co69.9Si12.5B9Fe5Cr3.5Mo0.1非晶丝的磁致伸缩系数λs为1′10-7。     

单晶Ni52Mn16．4Fe8Ga23．6的磁控形状记忆效应和磁感生应变

用磁悬浮冷坩埚提拉设备沿[001]方向生长了组分为Ni52Mn16.4Fe8Ga23.6的单晶,通过磁增强相变应变和磁感生应变的测量研究了该材料磁控形状记忆效应和磁感生应变的温度稳定性。结果发现该材料不但具有大的自发相变应变、磁增强相变应变和磁感生应变,而且磁感生应变具有很好的温度稳定性,从265K到100K,饱和磁感生应变的最大减小量不超过10％。另外,实验也发现磁感生应变量最大的方向是沿晶体母相的[001]方向(即单晶生长方向)。根据合金形状记忆的特点和磁场诱导应变的机理对实验结果进行了分析和讨论。     

添加微量B元素对Al19Co20Fe20Ni41共晶高熵合金显微组织及性能的影响

同时强化合金的力学性能和磁性能是软磁材料的理想化制备策略。通过制备非等原子比的Al19Co20Fe20Ni41共晶高熵合金,研究硼元素合金化对显微组织演变、相形成、力学性能和软磁性能的影响。随着B含量的增加,(Al19Co20Fe20Ni41)100-xBx合金的显微组织从最初的层片状共晶组织(x=0)转变为离异共晶组织(x>0.6)。细小的硼化物从晶间相中析出(x≥0.6)。合金的硬度从HV 328.66增加到HV 436.34。压缩力学性能测试结果显示合金发生从塑性材料向脆性材料的转变。Al19Co20Fe20Ni41合金具有良好的软磁性能,微量的B添加对其软磁性能的影响很微弱。当用作软磁性材料时,合金电阻率的增加可以有效地减少涡流损耗。     

Approximants in annealed IQC(Icosahedral Quasicrystal)-DQC(Decagonal Quasicrystal) pseudo-binary alloys

1　INTRODUCTIONWithnowadaysimprovementintheunderstand ingofthequasicrystallinematerial ,itspotentialap plicationshavebeengraduallypointedoutinvariousfieldsasthermalinsulation[1] ,lightabsorption[2 ,3] ,powergeneration[4 ] andhydrogenstorage[5,6 ] ,etc .Privatecompanieshaveshowngreatinterestespecial lyintheapplicationofitstribologyandthermo powergenerationproperties .Therefore ,betterunderstand ingofthescientificnaturesofquasicrystals (QCs)anditsapproximantisbelievedtobecomeagoodpaththatwi…     

铁纳米带半金属性的第一性原理研究

基于密度泛函理论(DFT)的投影缀加平面波(PAW)赝势第一性原理，探究了横截面为3×5、3×7、3×9、3×11、3×13和3×15原子层的铁纳米带的弛豫结构和电磁学性质。结果表明：所有6种尺寸的Fe纳米带的弛豫结构仍具有双重对称性，但3×5和3×7原子层的Fe纳米带的横截面形状从初始的矩形变为近椭圆形，而其他较宽尺寸的Fe纳米带的横截面形状都变为双椭圆形。并且，通过计算发现，3×7原子层的Fe纳米带是一种半金属材料，只有自旋向上或自旋向下的电子通过费米能级，因此可被应用于产生近100%自旋极化载流子的自旋电子学领域。     

退火温度对Nd2(FeGaCo)14B/α-Fe纳米复合材料磁性能的影响

用熔体快淬和晶化处理的方法制备了Nd2(FeGaCo)14B／α—Fe纳米复合材料，研究了晶化热处理温度和时间对材料磁性能的影响。结果表明Nd8Fe84.5Ga1Co2B4.5纳米复合材料的磁性能随热处理条件而变化，低温长时间和高温短时间热处理所得样品的最佳磁性能相当。     

High-strain-rate superplasticity of the Al–Zn–Mg–Cu alloys with Fe and Ni additions

During high-strain-rate superplastic deformation, superplasticity indices, and the microstructure of two Al–Zn–Mg–Cu–Zr alloys with additions of nickel and iron, which contain equal volume fractions of eutectic particles of Al₃Ni or Al₉FeNi, have been compared. It has been shown that the alloys exhibit superplasticity with 300–800% elongations at the strain rates of 1 × 10^–2–1 × 10^–1 s^–1. The differences in the kinetics of alloy recrystallization in the course of heating and deformation at different temperatures and rates of the superplastic deformation, which are related to the various parameters of the particles of the eutectic phases, have been found. At strain rates higher than 4 × 10^–2, in the alloy with Fe and Ni, a partially nonrecrystallized structure is retained up to material failure and, in the alloy with Ni, a completely recrystallized structure is formed at rates of up to 1 × 10^–1 s^–1.     

Enhancement of densification and sintering behavior of tungsten material via nano modification and magnetic mixing processed under spark plasma sintering

In the present study, the influence of nano additives (Ni, Fe) and different mixing (turbular and magnetic) on the densification, microstructure and micro-hardness of the tungsten material under spark plasma sintering is analyzed. After turbulent mixing the nanoparticles are distributed widely in the W interparticle gaps but after magnetic mixing the nanoparticles are distributed not only on the gaps of the W particles but also on the broken surfaces. Ni incorporated tungsten materials achieved the maximum density of 98.3% at 1400 °C (turbular mixing) and 97.9% at 1300 °C (magnetic mixing). Fe incorporated tungsten material showed density of 97.7% at 1600 °C and 97.2% at 1400 °C after turbular and magnetic mixing. The influence of nanoparticles in the densification process was explained by Laplace force, boundary slip and Agte-Vacek effect. The microstructural analysis showed that nano-modification reduced the degree of porosity, and provides a compact material at low temperatures. X-ray fluorescence analysis reveals that magnetic mixing shows more uniform distribution of nanoparticles than turbular mixing. The nanoparticles incorporation increased the micro hardness of tungsten material. Hence, it is clear that magnetic mixing and nano modification greatly improved the densification and sintering behavior of the tungsten material.     

WC—8（Fe／Ni／Co）R硬质合金的研究

用Ｆｅ、Ｎｉ部分取代ＷＣ－８Ｃｏ合金（牌号ＹＧ８）中的粘结剂Ｃｏ,再添加微量稀土Ｒ制得ＷＣ－８（Ｆｅ／Ｎｉ／Ｃｏ）Ｒ硬质合金,测试了其物理机械性能,研究了粘结剂各种成份比例及烧结温度对硬质合金的影响。结果表明：ＷＣ－８（Ｆｅ／Ｎｉ／Ｃｏ）Ｒ硬质合金的性能可以达到ＹＧ８的性能标准。利用扫描电镜（ＳＥＭ）及Ｘ射线衍射（ＸＲＤ）对其作了显微结构分析,同时探讨了影响ＷＣ－８（Ｆｅ／Ｎｉ／Ｃｏ）Ｒ合金性能的     

单晶Ni_(52)Mn_(24)Ga_(24)的磁感生应变和磁增强双向形状记忆效应

铁磁性Heusler合金Ni2 MnGa是近年开发的磁控制功能材料 ,已发现该材料结合马氏体相变可以产生大磁致伸缩 (磁感生应变 )和磁控制形状记忆效应两种应用功能。用磁悬浮冷坩埚提拉设备沿 [0 0 1]方向生长了组分为Ni52 Mn2 4 Ga2 4 的单晶。室温时沿该单晶样品 [0 0 1]方向加磁场 ,在该方向获得了 - 0 6 %的大磁感生应变。当磁场方向垂直于 [0 0 1]方向时 ,样品在 [0 0 1]方向的磁感生应变值为 0 5 %。同时该单晶样品在室温附近还具有可由磁场增强和控制的双向形状记忆效应。无磁场作用时 ,降低温度 ,样品在发生马氏体相变时 ,在 [0 0 1]方向产生1 2 %的收缩形变。随后升高温度 ,反马氏体相变时样品以同样的应变量膨胀 ,恢复到原来的形状 ,显示了特有的无需外应力协助的自发的双向形状记忆效应。其温度滞后只有 10℃。如果在样品的 [0 0 1]方向加一个偏磁场 ,其形状记忆的应变量随磁场的增强而增大。在磁场为 1 2T时可达 4%。而当磁场转向 [10 0 ]方向时 ,形状记忆的应变可以改变符号。本文指出产生大磁感生应变和磁增强双向形状记忆效应的关键是马氏体变体的择优取向。     

Effect of nucleating agents on synthesis of CoNi alloy particles via polyol process

CoNi alloy particles were synthesized via the polyol process using nucleating agents such as copper (II) acetylacetonate and K₂PtCl₄. The phase, morphology, mean size, and magnetic properties were evaluated using X-ray diffractometry, field emission scanning electron microscopy, and a vibrating samples magnetometer. At [Cu]/[Co+Ni]=1×10⁻⁶, the size of the CoNi alloy particles was approximately 320 nm. When the nucleation molar ratio [Pt]/[Co+Ni] was 8×10⁻⁵, the size decreased to 95 nm. This indicates that K₂PtCl₄ is a more effective nucleating agent for controlling the size of CoNi nanoparticles at the tens to hundreds of nanometers scale. The magnetic properties showed that the CoNi alloy particles are typical soft magnetic materials. The coercivity of CoNi alloy particles prepared by using K₂PtCl₄ as a nucleating agent was higher than of particles prepared by using copper (II) acetylacetonate.