注射成形高比重合金的性能与显微组织

含钨量较高的ＷＮｉＦｅ高比重合金具有高的密度、强度等优异性能,适合用作动能穿甲弹以及防辐射屏蔽材料;而粉末注射成形技术（ＰＩＭ）在生产小而形状复杂与性能良好的零件方面具有很大的潜在优势。研究了９５Ｗ３．５Ｎｉ１．５Ｆｅ高比重合金的注射成形工艺,讨论了其烧结工艺与性能的关系,并与采用传统粉末冶金（ＰＩＭ）法制造的合金性能与显微组织进行了比较。结果表明,采用注射成形所生产的合金,性能更高,硬度分布和显微组织结构更均匀。     

Formation of Fe-19 wt%Cr-9 wt%Ni Nanocrystalline Alloy with Excellent Corrosion Resistance: Phase Transition and Microstructure

In this paper, microstructure characteristics and phase transitions of Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy are comprehensively studied during the mechanical alloying and hot pressing sintering processes. Corrosion resistance of the sintered Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy samples is further analyzed. During the mechanical alloying process, Fe-19 wt%Cr-9 wt%Ni nanocrystalline alloy powders mainly composed of metastable ferrite phase are obtained after mechanical alloying for 8, 16 and 24 h, respectively. In the subsequent hot pressing sintering process, the phase transitions(from ferrite to austenite) occur from 650 to 750 °C for Fe-19 wt%Cr-9 wt%Ni alloy powders milled for 24 h. When the sintering temperature is raised to 1050 °C for 1 h, the ferrite phase has transformed into austenite phase completely, and the obtained grain size of sintered Fe-19 wt%Cr-9 wt%Ni alloy is around 40 nm. Electrochemistry test of the sintered Fe-19 wt%Cr-9 wt%Ni alloy has been operated in 0.5 mol L~(-1) H_2SO_4 solution to show the corrosion resistance properties. Results show that the sintered Fe-19 wt%Cr-9 wt%Ni alloy exhibits excellent corrosion resistance, which is proved by higher self-corrosion potential, lower self-corrosion current density and larger capacitive reactance, compared with that of commercial 304 stainless steel.     

Effects of phosphorus addition on the magnetic properties of sintered Fe-50 wt.% Ni alloys

Phosphorus was added to Fe-50 wt.% Ni in the form of a coated composite powder via an electroless plating process. Addition of phosphorus to Fe-50 wt.% Ni facilitated increases in density and grain size, both of which were beneficial to magnetic performance. Because of the homogeneous distribution of phosphorus in the powder, the optimal phosphorus addition was much lower than for those using Fe₃P as the phosphorus precursor. The optimal phosphorus addition was close to its maximum solubility in Fe-50 wt.% Ni (about 0.5 wt.%), above which precipitation of excessive phosphorus in the form of iron nickel phosphide, (Fe,Ni)₃P, effectively degraded the magnetic properties of Fe-50 wt.% Ni. Without the addition of phosphorus, good magnetic properties could be achieved only when the sintering temperature was high enough (>1200 °C) to result in a high sintered density and large grains in the sintered structure.     

Soft magnetic properties of (Ni50Fe50)SiO2 granular thin films for high frequency application

series of (Ni50Fe50)x(SiO2)(1-x) films with different volume fraction x was fabricated by magnetron co-sputtering technique. The microstructure, magnetic and electrical properties were investigated systematically by using X-ray diffraction, transmission electronic microscope, vibrating sample magnetometer and the traditional four point measurement method of resistivity. The results show that the samples consist of nano-scaled Ni50Fe50metallic particles with fcc structure uniformly embedded in amorphous insulating SiO2 matrix, and the particle size decreases with the decrease of x . The rapid change of coercivity with x is observed, and a minimum value 160 A·m-1 of Hc was obtained for the sample of x =0.83 with film thickness of 180 nm, which can be contributed to the exchange coupling between nano-scaled Ni50Fe50 particles. At the frequency lower than 1 GHz, the real part μ' of complex permeability keeps about 110 and the image part μ" is less than 15. Besides, this film exhibits high resistivity ρ=263 μΩ·cm, high saturation magnetization 4π Ms=1.25 T, high in-plane magnetic anisotropy field Hk=6.37 kA·m-1 , and the ferromagnetic resonance (FMR) frequency is estimated to be 2.8 GHz. Therefore, this film can be used in high frequency devices operating over 2 GHz.     

显微结构和杂质对金属注射成形Fe-50%Ni合金磁性能的影响

以羰基铁粉和羰基镍粉为原料,采用金属注射成形(MIM)工艺制备Fe-50%Ni软磁合金.通过对不同工艺条件下试样的杂质含量、密度、金相组织和磁性能的分析,研究显微结构和杂质对磁性能的影响.结果表明:孔隙是影响MIM Fe-50%Ni饱和磁感应强度的主要因素,孔隙、杂质和晶粒尺寸是影响磁导率和矫顽力的因素;最大磁导率、初始磁导率和矫顽力之间存在一定的联系,矫顽力可以作为最大磁导率和初始磁导率的参考依据.通过对比分析孔隙度、杂质含量和晶粒尺寸对矫顽力的影响规律,发现晶粒尺寸是影响MIM Fe-50%Ni合金矫顽力的主要因素.     

Study on Thermomagnetic Treatment Fe-25.5Cr-12Co Permanent Magnetic Alloy

The magnetic properties and microstructure in a low cobalt Fe-25.5Cr-12Co alloy by different process of thermomagnetic treatment were investigated. It is found that magnetic properties are sensitive to parameters of thermomagnetic treatment process in magnetic field, including temperature, time and applied magnetic field. There are optimized isothermal aging temperature and time in different magnetic heat treatment conditions. High magnetic field strength could improve magnetic properties. Applied magnetic field has a great effect on microstructure of the Fe-25.5Cr-12Co alloy. The finer ferromagnetic α１ particles with suitable c/a ratio by high magnetic field magnetic heat treatment are attributed to improvement the magnetic properties.     

添加剂对低压烧结Zr50Al15Ni10Cu25非晶态粉末力学性能的影响

以商业纯元素粉末为原料,用机械合金化方法在低真空条件下合成了以非晶态为主的Zr50Al15Ni10Cu25粉末。研究了一定量的外界添加剂C、Si3N4和SiC对体系热稳定性和晶化行为的影响。混合粉末用手工预压成形,然后在氩气氛下进行低压烧结。利用X射线衍射（XRD）、扫描电镜（SEM）、差热分析（DSC）和电子拉伸实验机对粉末样和块状样进行了测试。结果表明,合适的外界添加剂可以提高体系的析晶活化能,增强体系的热稳定性。适量的Si3N4能促进Zr50Al15Ni10Cu25非晶粉末的低压烧结性能,即有助于提高样品的烧结致密度和样品的抗弯强度。     

New Fe-based soft magnetic amorphous alloys with high saturation magnetization and good corrosion resistance for dust core application

Fe-rich amorphous dust core alloys with minor-addition of Mo and/or Cr were synthesized because of the industrial request of mass production of high efficient low core loss Fe-based dust cores. It was found that the present Fe-(Cr, Mo)-P-B-Si-(C) amorphous alloy ribbons exhibit good soft magnetic properties of above 1.5 T for saturation magnetization, below 10 A/m for coercivity and rather good corrosion resistance in 3%NaCl aqueous solution. Besides, the amorphous alloy ribbons exhibit good bending ductility in as-spun and optimally annealed states. It is noticed that these characteristics are much superior to those for commercial Fe-Cr-Nb-P-B-Si soft magnetic dust core alloy (SENNTIX). In addition, the annealing treatment was noticed to cause the improvement of corrosion resistance without detriment to bending ductility. The new Fe-based soft magnetic alloys with good combined characteristics are expected to be used as the basic material as high-efficient soft magnetic dust cores in a high frequency range.     

Preparation of isotropic Sm2Fe17Nx magnetic powders and their bonded magnets

The isotropic Sm2Fe17Nx magnetic powders were prepared by Hydrogenation-Disproportion-Desorption-Recombination (HDDR) process. The phase and microstructure evolutionary process of Sm-Fe alloy during the solidification, homogenization, HDDR and nitration processes were investigated by means of XRD, SEM, EDX and AFM. The results show that the homogeneous Sm2Fe17 alloy wassuccessfully obtained and the impurity phases and residual stress were well removed by heated at 1050 ℃ for 24 h. When heated at 800 ℃ for 1h in H2 of 0.1 Mpa, the alloy turns into SmHx and α-Fe with plenty of nanocrystals. After vacuumized at 800 ℃ for 2h the alloy recombines into Sm2Fe17 with a crystal grain size of about 85 nm.The lattice constant of the alloy increases and the expanding of the crystal cell reaches 6.28% after nitrified at 500 ℃ for 5 h. The magnetic property of isotropic bonded Sm2Fe17Nx magnets is Br=0.6704 T, Hcj = 1015 kA·m-1,( BH )max =73.7 kJ·m-3 with a density of 6.04 g·cm-3 .     

Fe—Mn─Al合金的腐蚀性能与钝化膜的研究

应用阳极极化及ＡＥＳ／ＸＰＳ技术,研究了Ｆｅ－３０．８Ｍｎ－８．２Ａｌ奥氏体合金在ｐＨ值为－０．８至１５．３的水溶液中的腐蚀性能,并与Ｆｅ－３０Ｍｎ合金、低碳钢、９％Ｎｉ低温钢及１Ｃｒ１３不锈钢进行对比。在所测试的水溶液中,该合金的腐蚀抗力优于低碳钢和Ｆｅ－３０Ｍｎ合金,与９％Ｎｉ钢相当,但不及１Ｃｒ１３不锈钢。Ｆｅ－３０．８Ｍｎ－８．２Ａｌ合金在１ｍｏｌ／ＬＮａ２ＳＯ个中形成的钝化膜的最表层可能为氢氧化物,而膜的主体由Ｆｅ２Ｏ３、Ｍｎ２Ｏ３及Ａｌ２Ｏ３组成。     

Ni合金化对Finemet合金热稳定性及软磁性能的影响

通过铜辊甩带法制备了成分为Fe_73.5-xSi_13.5B₉Cu₁Nb₃Ni_x(x=0、1、2、3)的非晶带材,并对其进行退火处理。利用XRD、DSC、VSM和软磁直流测试仪等对带材的相结构、热稳定性以及软磁性能进行测试分析。结果表明,所制备合金带材淬火态下均为完全非晶结构,经560 ℃保温60 min退火处理后,合金中形成了非晶和α-Fe(Si)纳米晶双相共存结构。随着Ni含量的增加,整体上非晶带材的一级起始晶化温度T_s1和二级起始晶化温度T_s2先减小后增大,两级起始晶化温度之差ΔT_s整体呈下降的趋势,由166.0 ℃下降至132.8 ℃,热稳定性降低。淬火态下,Ni元素的添加使得非晶带材的软磁性能有所恶化。经退火处理后,带材的软磁性能明显提升,当Ni含量x=1时,具有较好的软磁性能,其饱和磁化强度为157.7 emu/g,矫顽力为6.8 Oe。     

机械合金化制备Fe-10%Ni合金研究

采用纯Fe粉和Ni粉利用高能卧式搅拌球磨机制备了Fe-10%Ni(质量分数,下同)合金,利用X射线衍射(XRD)、扫描电子显微镜(SEM)、差热分析(DTA)研究了球磨粉末的相组成、形貌和热稳定性,并对其热压烧结的块材进行了组织分析与性能测试。结果表明,在球磨机转速400 r/min,球料比20:1条件下,球磨8 h后,Ni原子完全固溶在Fe原子晶格中,形成体心立方结构Fe(Ni)过饱和固溶体,延长时间到16 h,球磨粉末颗粒尺寸更均匀细小,但仍为体心立方Fe(Ni)固溶体。对球磨16 h的合金粉末在500~800℃进行退火处理,发现粉末结构稳定,仍为体心立方Fe(Ni)固溶体。对球磨16 h的合金粉末进行热压烧结,发现950℃下烧结块材中出现少量fcc结构的Fe(Ni)固溶体相,而继续在970℃复烧后则完全转变为面心立方结构的Fe(Ni),但950℃热压烧结块材的强度和延伸率高于970℃复烧的块材,原因在于无压复烧块材中产生氧化物和孔洞。     

Enhanced sintering of an Fe-Ni-P coated composite powder prepared by electroless nickel plating

An Fe-8.2 % Ni-6.0 % P powder was prepared by electroless nickel plating on a carbonyl iron powder, where phosphorous appeared as a contaminant of the plating process. Because of the high phosphorous concentration, persistent liquid phase sintering was effective at temperatures higher than 1000 °C. The sintered microstructure was dramatically different from the conventional approaches, where a low concentration of phosphorous was added in the form of Fe₃P. Sintering the alloy at a temperature as low as 1050 °C for 30 min yielded a sintered density of 98.6% theoretical and rounded grains having an average grain size of 53 μm. The rounded grains were surrounded by a large volume fraction of intergranular (Fe,Ni)₃P phase, arising from the high phosphorous concentration, which slightly deteriorated the magnetic saturation but significantly increased the electrical resistivity of the alloy. Generally speaking, the magnetic saturation of the sintered alloy was improved with respect to the iron-phosphorus, iron-nickel, or iron-silicon alloys fabricated by powder processing.     

Fabrication of nano-crystalline W-Ni-Fe alloy with Mo and rare earth element additives

Three kinds of nano-crystalline high density alloys (86W-7Ni-3Fe-4Mo, 90W-4Ni-2Fe-4Mo and 90W4Ni-2Fe-3.8Mo-0.2RE) were fabricated by a technique combining lower temperature vacuum sintering with highenergy ball milling mechanical alloying. The crystalline size and microstructures of the specimens sintered at different sintering temperatures were examined by X-ray diffraction(XRD) and scanning electron microscope(SEM). The results show that the optimal sintering temperature of 86W-7Ni-3Fe-4Mo, 90W-4Ni-2Fe-4Mo and 90W-4Ni-2Fe-3.8Mo-0.2RE alloys are 1 300 - 1 350℃. When they are sintered at 1 300℃ for 75 min， the hardness of three kinds of specimens can reach above HRC30, the relative density can reach above 96%, and 90W-4Ni-2Fe-3.8Mo-0.2RE alloy possesses the best integrated properties, its hardness is HRC35 and its relative density is 98%.     

Effect of heat treatment on structure and magnetic properties of Fe65.5Cr4Mo4Ga4P12C5B5.5 bulk amorphous alloy

This study deals with the Fe65.5Cr4Mo4Ga4P12C5B5.5 ferromagnetic bulk amorphous alloy. XRD analysis showed an amorphous structure of the as-cast sample. The same method revealed that, after annealing at 973 K for τ=10 min, the sample displayed a crystalline structure with crystalline phases formed. The crystallization process of the alloy was examined by DTA analysis. It was shown that crystallization took place in the temperature range between 810 K and 860 K with the exo-maximum peak temperature at 846 K with a heating rate of 20 K·min-1. The method also showed that, at temperatures ranging from 753 K to 810 K, the alloy exhibited the properties of supercooled liquids. A correlation between heat-induced structural changes and magnetic properties of the alloy was determined by thermomagnetic measurements. Maximum magnetization M=3.7 Am2·kg-1 of the alloy was reached after its annealing at 733 K for τ=10 min. Upon annealing, the alloy exhibited a relaxed amorphous structure. Annealing the alloy above the crystallization temperature led to a decrease in bulk magnetization. After annealing at 973 K for τ=10 min, the bulk magnetization of the alloy was M'=0.45 Am2·kg-1. Accordingly, after crystallization and formation of new compounds, the magnetization of the alloy was decreased by a factor of about 7.7. The strength of the magnetic field applied during the measurements was H=10 k A·m-1. The samples were tested for changes in the microstructure and hardness of both the amorphous phase and the resulting crystalline phase.     

新型生物可降解Fe-30Mn-1C合金的性能研究

采用真空感应熔炼法制备了Fe-30Mn-1C合金,研究了其力学性能、磁性、模拟体液中的降解速度以及体外生物相容性.研究结果表明,与Fe-30Mn合金和316L不锈钢相比,C的加入提高了铁基合金的力学性能,使材料兼具高强度和高塑性,并进一步降低了材料的磁性,使其具有更优良的核磁共振(MRI)兼容性.电化学阻抗谱(EIS)结果表明,材料的极化电阻降低,浸泡实验也证实材料的降解速度得到提高.体外生物相容性研究结果表明.Fe-30Mn-1C合金同时具有优异的抗溶血、凝血、血小板黏附性能,以及良好的细胞相容性,满足对医用植入材料的基本要求.     

注射成形高密度合金的变形控制

研究了注射成形高密度合金的变形行为和变形控制。实验表明,在液相烧结过程中,由于重力作用导致粘性流动,合金试样发生变形。对W含量较高的合金,采用二步烧结工艺可以有效地控制变形。在此工艺中,压坯首先在粘结相熔点以下温度烧结,形成W连通骨架,然后在高于粘结相熔点以上的温度下烧结较短时间以达到全致密;对于W含量较低的高密度合金,将原始混合粉末采用机械合金化,然后再进行固相烧结,可以得到性能很高的无变形的合金。     

Finished surface morphology,microstructure and magnetic properties of selective laser melted Fe-50wt% Ni permalloy

This work focuses on the structure and magnetic properties of Fe-50wt% Ni permalloy manufactured from the pre-alloyed powder by selective laser melting (SLM). The selective laser melted (SLMed) alloys were characterized by a 3D profilometer, optical microscope, scanning electron microscope, X-ray diffraction, etc. The effects of the volume energy density of laser (LVED) on structure, and magnetic properties with coercivity (H_c), remanence (B_r), and power losses (P_50-1), were evaluated and discussed systematically. The results show that the relative porosity rate and the surface roughness of the SLMed specimens decreased with the increase in LVED. Only the γ-(FeNi) phase was detected in the X-ray diffraction patterns of the SLMed permalloys fabricated from the different LVEDs. Statistical analysis of optical microscopy images indicated that the grain coarsened at higher LVED. Furthermore, the microstructure of the SLMed parts was a typical columnar structure with an oriented growth of building direction. The highest microhardness reached 198 HV_0.1. Besides, the magnetic properties including B_r, H_c, and P_50-1 of SLMed samples decreased when the LVED ranged from 33.3 to 60.0 J/mm³ firstly and then increased while LVED further up to 93.3 J/mm³, which is related to the decrease in porosity and the increase in grain size, while the higher residual stress and microcracks presented in the samples manufactured using very high LVED. The observed evolution of magnetic properties and LVED provides a good compromise in terms of reduced porosity and crack formation for the fabrication of SLMed Fe-50wt% Ni permalloy. The theoretical mechanism in this study can offer guidance to further investigate SLMed soft magnetic alloys.     

INJECTION MOLDED TUNGSTEN HEAVY ALLOY

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Magnetic properties of nanocrystalline Ni3Fe compacts prepared by spark plasma sintering

Nanocrystalline Ni₃Fe compacts were successfully prepared by spark plasma sintering starting from wet mechanically alloyed powders. The influences of the sintering conditions: sintering temperature, sintering time and particle size on the compact magnetic properties are investigated. It is found that high sintering temperature, increased sintering duration and larger particle size leads to compacts with improved soft magnetic properties. A contamination with carbon of the compacts during the sintering processes has been found to reduce their magnetic properties. It is found that a heat treatment at the temperature of 450 °C during 4 h, in hydrogen atmosphere, leads to an improvement of the compact coercivity and of the maximum relative permeability of the compact to up to 600% and 50% respectively. Spark plasma sintering can consequently be considered as promising compaction technique for processing Ni₃Fe nanocrystalline powder in particular and nanocrystalline soft magnetic alloys in general.