Powder injection molding of Fe-Ni soft magnetic alloys

With miniaturization and complication of the shape of electronic devices in recent years,powder injection molding(PIM)seems to be a suitable process for fabricating the higher performance soft magnetic components.In this paper,high quality Fe-50Ni soft magnetic alloy was fabricated by PIM with carbonyl iron and nickel,and the effect of sintering process on its microstructure and magnetic properties were investigated.The mechanical and magnetic properties can be obviously improved by increasing the sintering temperature or using the hydrogen atmosphere instead of high vacuum,which causes by the increase of grain size and the densification.At the optimum sintering conditions,the PIM Fe-50Ni soft magnetic alloy with high properties are obtained,whose relative density,tensile strength,B_(m),H_(c),μ_(m)are 97%,465 MPa,1.52 T,16.62 A·m^(-1),42.5 mH·m^(-1),respectively.

Magnetic Properties of Nanocrystalline Fe_(60)Cr_(40) Powders Prepared by Mechanical Alloying in Vacuum and Air

Magnetic properties of nanocrystalline Fe_~60 Cr_~40 powders prepared by mechanical alloying in vacuum and air were investigated by utilizing the measurements of magnetization, X-ray diffraction, and ~ ~57 Fe Mssbauer spectrum. The results show that the Fe_~60 Cr_~40 powders keep the bcc structure during milling in air and vacuum. The saturation magnetization of the Fe_~60 Cr_~40 powders milled in vacuum and air decreases with the increase of the milling time up to 45 h. The decrease of saturation magnetization of the Fe_~60 Cr_~40 powders milled in vacuum is due to the formation of Fe-Cr solid solution, while in air it is due to the formation of paramagnetic disorder structure and solid solution.

Influence of Ni^(2+)/Co^(2+)ratio in electrolyte on morphology,structure and magnetic properties of electrolytically produced Ni-Co alloy powders

Nickel-cobalt(Ni-Co) alloy powders were produced galvanostatically by using sulphate electrolytes with various ratios of Ni2+/Co2+(mole ratios). The morphology, phase structure, chemical composition and magnetic properties were examined by scanning electron microscope(SEM), X-ray diffractometer(XRD), atomic emission spectrometer(AES), and SQUID-based magnetometer, respectively. Morphology of the particles changed from cauliflower-like and dendritic to coral-like and spongy-like ones with increasing Ni2+/Co2+ ratio from 0.25 to 4.0. XRD analysis of the Ni-Co powders revealed that the decrease of Ni2+/Co2+ ratios(the increase of Co content) caused a change of structure from face centered cubic(FCC) obtained for the ratios of 4.0, 1.5 and 0.67 to a mixture of FCC and hexagonal closed-packed(HCP) phases for the ratio of 0.25. The increasing content of nickel led to change of mechanism of electrolysis from irregular(up to 40 wt.% Ni in the electrolytes) to close to equilibrium(between 40 and 60 wt.% Ni in the electrolytes) and anomalous co-deposition(over 60 wt.% Ni in the electrolytes) type. All of the obtained Ni-Co alloy samples behaved as soft magnetic materials while their magnetic parameters showed immediate composition dependence since both coercivity and saturation magnetization almost linearly increased with increase of the Co content.

Fabricating functionally graded Fe-Cr-Co permanent magnetic alloys via laser powder bed fusion

Laser powder bed fusion(LPBF)in-situ alloying technology offers the possibility to construct gradient materials with varied structures and properties.Functionally graded Fe-Cr-Co permanent magnetic alloys were fabricated by LPBF and in-situ alloying mixed powders of Fe,Cr,and Co elements.The effects of different Fe,Cr and Co contents on the microstructure,magnetic properties and hardness of Fe-Cr-Co alloys prepared by LPBF were studied.The as-built Fe-Cr-Co alloys present a single body-centered-cubic phase and have a homogeneous distribution of elements.The mechanical properties and magnetic properties of the compositionally graded sample show a gradient variation.With the increase in Cr content,the Vickers hardness of the sample increases,and the saturation magnetization of the sample decreases.The optimal magnetic properties in an isotropic state are given as coercivity HcB=21.65 kA/m,remanence Br=0.70 T and energy product(BH)_(max)=5.35 kJ/m^(3),which are comparable to or higher than the reported magnetic properties in an isotropic state prepared by traditional powder metallurgy.LPBF in-situ alloying technology has the potential to further explore Fe-Cr-Co magnetic materials,such as those consisting of multiple or more constituent elements,and to maximize the compositional flexibility of magnetic materials.

Evaluation of Mean Crystallite Size on Magnetic Powder by Scanning Electron Microscopy and Synchrotron Diffractometry

This paper presents the results of investigations carried out with Pr-based magnetic powders. The magnetically hard powders were produced from homogenised alloys using a high temperature hydrogen pulverization process. Alloys and powders were investigated by scanning electron microscopy and by energy dispersive X-ray analysis. Mean crystallite size of the pulverized material was estimated using synchrotron powder diffractometry and the Scherrer method. A comparison between these two investigation techniques has been carried out. The effects of copper on the properties of the magnetic powders have been studied. It has been shown that the addition of this alloying element had a marked effect on the microstructure of the powders.

Investigation of Fe-Ni-B and Fe-Cr-B Ultrafine Amorphous Alloy Powders Prepared by Chemical Reduction

Ultrafine amorphous alloy powders of spherical shape with diameters from 10 to 50nm for Fe-Ni-B and Fe-Cr-B were prepared by chemical reduction. The amorphous structure of two powders was identified by X-ray diffraction. The B concentrations for the two alloy systems did not change dramatically, as the preparation condition changed. An oxide film covered up the powders. The maximum magnetization decreased as increasing the content of Ni or Cr.

核壳式球形铁基磁性磨料的制备及其抛光性能

[目的]混合式和镶嵌式磁性磨料的尺寸效应,以及磨粒出刃高度不一致所引起的抛光硬冲击问题亟待解决。[方法]将不规则铝粉与球形羰基铁粉均匀混合,通过加热扩散在接触界面生成金属间化合物并均匀分布在球形羰基铁粉表面,从而形成铁/铝核壳式球形磁性磨料,随后用它对氟化钙基片进行抛光。[结果]通过单因素试验优选出制备该核壳式铁基磁性磨料的最佳工艺参数为:反应时间4 h,反应温度770℃,Al含量质量分数12%。X射线衍射(XRD)、扫描电镜(SEM)观察、能谱(EDS)分析和磁化强度测试表明所得磁性磨料以羰基铁粉为内核,Fe Al、Fe_(3)Al、Fe_(0.4)Al_(0.6)等金属间化合物为壳,粒度符合正态分布,磨料相外壳分布均匀且出刃高度较为一致。氟化钙晶体经铁/铝核壳式磁性磨料抛光后表面变得光滑、平坦,粗糙度均方根值由初始的1.102μm下降到33 nm。[结论]所制备的核壳式球形铁基磁性磨料可用于软脆材料的磁力抛光。

磷酸含量对FeSiCr@磷酸盐/硅酸钠软磁粉芯性能的影响

基于粉末冶金工艺制备FeSiCr@磷酸盐/硅酸钠软磁粉芯,采用扫描电镜(SEM)、X射线衍射(XRD)与盐雾等实验方法与损耗分离计算,探究不同磷酸含量(质量分数为0~1.5%)对FeSiCr复合粉芯软磁性能与耐蚀性的影响。研究结果表明,适度增加磷酸含量,可提高磁粉芯相对密度与直流偏置性能,并显著降低磁粉芯损耗。但过高的磷酸含量会降低绝缘层均匀性,增加磁畴壁运动的阻力,导致磁粉芯损耗增加与磁导率下降。此外,磁粉芯耐蚀性也随磷酸含量增加而下降。当磷酸质量分数为1.0%时,FeSiCr磁粉芯具备最优综合软磁性能,磁导率为38.3(100 kHz时),损耗为646.24 mW/cm^(3)(1 MHz与20 mT时)。

Iron-nickel alloy particles with N-doped carbon “armor” as a highly selective and long-lasting catalyst for the synthesis of Nbenzylaniline molecules

A scalable strategy for the convenient and rapid preparation of nitrogen-doped carbon-coated iron-based alloy catalysts was developed.By controlling the type and amount of metal salts in the precursor,various types of nitrogen-doped carbon-coated alloy catalysts can be prepared in a targeted manner.Fe_(2)Ni2@CN materials with small particle sizes and relatively homogeneous basic sites showed promising results in the N-alkylation reaction of benzyl alcohol with aniline(optimum yield:99%).It is worth noting that the catalyst can also be magnetically separated and recovered after the reaction,and its performance can be regenerated through simple calcination.Furthermore,it was confirmed by kinetic experiments that the activation of C–H at the benzyl alcohol benzylic position is the rate-determining step(RDS).According to density flooding theory calculations,Fe_(2)Ni2@CN catalysts require less energy than other materials(Fe@CN and Ni@CN)for the RDS(dehydrogenation reaction)process.Therefore N-alkylation reactions are more easily carried out on Fe_(2)Ni2@CN catalysts,which may be the reason for the best catalytic activity of Fe-Ni alloy materials.These carbon-coated alloy materials will show great potential in more types of heterogeneous catalysis.

Laser additive manufacturing of strong and ductile Al-12Si alloy under static magnetic field

Rapid cooling and solidification during laser additive manufacturing(LAM)can produce ultra-fine microstructure with higher strength.However,the non-uniform cell/grain structure can easily result in early stress concentration and fracture during deformation,which remains a major challenge for the LAM field.Using Al-12Si as the model alloy,we employed the external static magnetic field(SMF)to modulate the laser powder bed fusion process(L-PBF),demonstrating a uniform microstructure with a refined cell structure.The mechanical properties show that the SMF can produce a combination of high tensile strength of 451.4±0.5 MPa and large uniform elongation of 10.4%±0.79%,which are superior to those of previously-reported Al-Si alloys with post-treatment or element alloying.The mechanism analysis based on multi-scale simulation reveals the determining role of SMF in rapid solidification,and this method is applicable to the microstructure control of other metallic materials during LAM.

Novel CoFeAlMn high-entropy alloys with excellentsoft magnetic properties and high thermal stability

High-entropy alloys(HEAs),which are composed of 3d transition metals such as Fe,Co,and Ni,exhibit an exceptional combination of magnetic and other properties;however,the addition of non-ferromagnetic elements always negatively affects the saturation magnetization strength(M s).Co_(4)Fe_(2)Al_(x)Mn_(y) alloys were designed and investigated in this study to develop a novel HEA with excellent soft magnetic properties.The Co_(4)Fe_(2)Al_(1.5)Mn_(1.5) HEA possesses the highest M s of 161.3 emu g^(-1) thus far reported for magnetic HEAs,a low coercivity of 1.9 Oe,a high electrical resistivity of 173μΩ cm,a superior thermal stability up to 600℃,which originates from the novel microstructure of B2 nanoparticles distributed in a DO_(3) matrix phase,and the crucial transition of Mn from antiferromagnetism to ferromagnetism with the assistance of Al.The Co_(4)Fe_(2_)Al_(1.5)Mn_(1.5) HEA was selected to produce micron-sized powder and soft magnetic powder cores(SMPCs)for application in the exploration field.The SMPCs exhibit a high stable effective perme-ability of 35.9 up to 1 MHz,low core loss of 38.1 mW cm^(-3)(@100 kHz,20 mT),and an excellent direct current(DC)bias performance of 87.7%at 100 Oe.This study paves the way for the development of soft magnetic HEAs with promising applications as magnetic functional materials.

热处理对Fe−6.5%Si磁粉芯性能的影响

对Fe-6.5%Si粉末(质量分数)进行不同温度的热处理实验,经压制后得到Fe-6.5%Si磁粉芯,并对磁粉芯进行不同温度的热处理,探究热处理工艺对Fe-6.5%Si磁粉芯磁导率和损耗等磁性能的影响。结果发现:粉末热处理可以大幅度消除气雾化制粉过程中合金粉末受高压气体冲击造成的缺陷,并减少粉末中的C、O含量;随着热处理温度的升高,粉末的矫顽力先增后减,饱和磁化强度逐渐降低。通过对压制成型磁粉芯进行热处理也能够改善磁粉芯的磁性能,不同温度热处理后损耗均维持在600~700 mW∙cm^(-3)之间,最低值为625 mW∙cm^(-3)。综合分析,用经900℃热处理粉末制成的磁粉芯在800℃进行后续热处理,磁粉芯磁导率、损耗等性能综合较优。

气雾化FeSi合金粉末制备及其磁粉芯磁性能研究

FeSi合金是一种性能优异的软磁材料,具有较高的饱和磁化强度,较低的磁损耗,较低的成本和磁芯设计灵活等特点,在开关电源、电动汽车以及光伏产业应用广泛。本文采用气雾化方法制取FeSi合金粉末,利用激光粒度分析仪、扫描电子显微镜(SEM)、电感耦合等离子发射光谱仪(ICP)、ONH-3000氮氧仪和金属粉末松装密度测定仪检测和分析粉末的粒度分布、形貌、物理化学性能。结果发现FeSi软磁合金粉末具有颗粒球形度高,松装密度高,氧含量低和粒度分布较均匀等特点。采用无机包覆的方式将FeSi软磁合金粉末制备成FeSi磁粉芯,通MATS-2010SD/K100软磁直流测量装置和MAZ513080SA/1M软磁材料动态测量装置研究了FeSi磁粉芯的磁性能以及磁损耗,结果显示,在5000A/m的磁场下,饱和磁化强度为0.6T;在50kHz下磁损耗达到110mW/cm^(3),具有良好的软磁性能。

Influence of dysprosium substitution on magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets prepared by double-alloy powder mixed method

The double-alloy powder mixed method is very proper for developing new small-mass products by changing the composi- tion of sintered Nd-Fe-B magnets, and there is little research on this aspect. The variation on magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets prepared by double-alloy powder mixed method was discussed, which is a method blend- ing two-type main phase alloy powders with different components. The results showed that the intrinsic coercivity and density of sin- tered Nd-Fe-B magnets increased gradually with the increase in Dy content, and the double-alloy powder mixed method could obtain high intrinsic coercivity Nd-Fe-B magnets with good crystallographic alignment and microstructure. The bending strength of sintered Nd-Fe-B magnets declined, and the Rockwell hardness of sintered Nd-Fe-B magnets first declined, and then increased with the in- crease in Dy content. The microstructure showed that there existed the phenomenon that the Dy element diffused into main phase dur- ing sintering process, and the distribution of Dy content in main phase had some variation in homogeneity as a result of incomplete reaction between the double-alloy powder types.

Laser Powder Bed Fusion Processing of Soft Magnetic Fe–Ni–Si Alloys: Effect of Hot Isostatic Pressing Treatment

Laser powder bed fusion(L-PBF)-processed high-silicon steel has great advantages in freely designed electric engines,and various studies have been conducted in this field.However,the analysis of both the mechanical and magnetic properties,focusing on the multiscale microstructure under as-fabricated and heat-treated conditions,which is indispensable for industrial applications,has not been performed.In this study,an Fe–Ni–Si sample was fabricated using the L-PBF process.Subsequently,the following hot isotropic pressing(HIPing)process was employed as a post heat treatment step for the Fe–Ni–Si alloys.The effects of HIPing on the microstructure were investigated,focusing on the metastable stable phase transformation in the Fe–Ni–Si system.X-ray diffraction results showed single-phase fccγ(Fe,Ni)in the L-PBF-processed samples before and after HIPing.Moreover,the acicular Ni/Si-rich structure(formed in the as-fabricated L-PBF sample because of its high cooling rates)transformed to the equilibrium austenite,Ni3Si,and FeNi3 phases during HIPing.After HIP,the compressive modulus and strength increased from 11 GPa and 650 MPa to approximately 18 GPa and 900 MPa,respectively.The magnetic properties were evaluated via a hysteresis loop,and the coercivity increased from 1.8 kA/m and to 2.9 kA/m after the HIPing process.

Fe-Cr-Si-B-C合金粉末非晶形成能力及其软磁性能

针对雾化Fe-Cr-Si-B-C合金粉末的非晶形成能力及软磁性能进行了分析。结果表明,从热力学角度而言,该成分合金具有较大的液固转变吉布斯自由能,且混合焓、混合熵、原子半径差异等参数值较好地满足高非晶形成能力的成分设计要求;从动力学角度而言,该合金的高非晶形成能力和高热稳定性主要源于其相对较高的结晶成核和晶体生长表观激活能;同时,Fe-Cr-Si-B-C非晶软磁合金粉末具有良好的软磁特性,饱和磁化强度和矫顽力分别为157.41 emu/g和0.65 Oe,复合粉心在1 MHz处有效磁导率为16.8,品质因数为96.8,且在100 Oe直流偏置场作用下磁导率维持在87.8%的水平。

高能球磨对雾化磁粉结构与磁性能的影响

采用高能球磨的方法处理水雾化Fe-Si-Al软磁合金粉末，运用SEM、XRD分析球磨粉末的显微结构和晶体结构，测试粉末的静磁参数及其2～18GHz范围的复磁导率（μr=μ′-jμ″）。结果表明，球磨时间增加，粉末的扁平率增大、粒度减小；平均晶粒尺寸减小、内应变增大导致结晶有序度降低；粉末的饱和磁感应强度减小、矫顽力增大；球磨粉末的复磁导率实部和自然共振频率均相应提高，但过度球磨不利于材料磁损耗性能的提高。

粉末特性对烧结Sm_2(Co、Fe、Cu、Zr)_(17)合金磁性能的影响

为深入了解烧结Sm2 (Co、Fe、Cu、Zr) 17合金磁性能与所用粉末特性的关系 ,通过设计不同球磨工艺 ,对不同滚动球磨条件下所制粉末进行了粒度和氧含量的测量 ,观察了滚动球磨与振动球磨两种方式下所制粉末的颗粒形状。研究了粉末粒度与形状对合金磁性能的影响。实验结果表明 ,粉末粒度在 4～ 6 μm时对应的合金磁性能最高 ;粒度≥ 6 μm时 ,随粒度增大磁性能下降 ;粒度≤ 4μm时 ,随粒度减小磁性能下降 ;

水雾化Fe_(69)Ni_5Al_4Sn_2P_(10)C_2B_4Si_4非晶合金粉末及其磁粉芯的性能

Fe69Ni5Al4Sn2P10C2B4Si4合金具有强的非晶形成能力，可以通过水雾化方法获得粒度小于75μm的非晶态合金粉末。用粒度45～75μm的水雾化粉末制备的磁粉芯具有优异的磁性能，磁导率大于60，良好的频率特性、高的品质因数和低的损耗。该磁粉芯与磁导率相等的韩国MPP磁粉芯产品相比，其综合性能更优越。

Fe-Si-Al系合金粉微波吸收特性

采用扁平化工艺以及绝缘包覆工艺对铁硅铝系软磁合金粉末进行改性。对实验样品进行扫描电镜分析，观察颗粒形貌对材料性能的影响；探讨球磨时间以及不同绝缘介质含量对于材料电磁性能的影响规律。根据单层吸波材料（含导电衬底）对电磁波的反射率公式的分析以及对不同样品反射率的计算可知，球磨扁平化工艺以及绝缘包覆工艺可有效地改善铁硅铝金属粉末的微波吸收性能。经改性后的铁硅铝系软磁金属粉末在1．0～3．5GHz频段具有较好的吸波性能，可应用于抗电磁干扰领域。