高温高强度Fe-Co软磁合金研制

随着飞机性能提高,航空发电机作为飞机电力核心设备,其转速不断提高,要求制作转子零件的高饱和磁感应强度Fe-Co合金具有更高的强度和韧性,并保持足够的磁性能和抗高温性能。介绍了高温、高强度Fe-Co合金的研制进展情况,着重研究并比较了新型FeCo、改进型1J22和低矫顽力型FeCo 3种合金的磁性能和力学性能随热处理温度变化的关系。其中,760℃热处理的新Fe-Co合金的抗拉强度σb=1 190 MPa,屈服强度σ0.2=610 MPa,延伸率δ5=15.0%,饱和磁感应强度Bs=2.231T,矫顽力Hc=134.2A/m,在磁性能和1J22相比基本不劣化的条件下,力学性能提高将近一倍,使用温度可以达到500℃,已经达到了新型先进飞机主发电机转子的设计技术指标要求。对于新合金的强化机理最后做了探索性的分析和讨论。     

Nanocrystalline materials for high temperature soft magnetic applications: A current prospectus

Conventional physical metallurgy approaches to improve soft ferromagnetic properties involve tailoring chemistry and optimizing microstructure. Alloy design involves consideration of induction and Curie temperatures. Significant in the tailoring of microstructure is the recognition that the coercivity, (H _c) is roughly inversely proportional to the grain size (D _g) for grain sizes exceeding ∼0·1−1 μm (where the grain size exceeds the Bloch wall thickness,δ). In such cases grain boundaries act as impediments to domain wall motion, and thus fine-grained materials are usually harder than large-grained materials. Significant recent development in the understanding of magnetic coercivity mechanisms have led to the realization that for very small grain sizesD _g<∼100 nm,H _c decreases sharply with decreasing grain size. This can be rationalized by the extension of random anisotropy models that were first suggested to explain the magnetic softness of transition-metal-based amorphous alloys. This important concept suggests that nanocrystalline and amorphous alloys have significant potential as soft magnetic materials. In this paper we have discussed routes to produce interesting nanocrystalline magnets. These include plasma (arc) production followed by compaction and primary crystallization of metallic glasses. A new class of nanocrystalline magnetic materials, HITPERM, having high permeabilities at high temperatures have also been discussed.     

Fe-Si-B-P-Mo系高饱和磁感应强度非晶软磁合金

通过在Fe-Si-B-P合金体系中微合金化添加Mo元素,并提高铁含量,成功制备了具有较强非晶形成能力和优异软磁性能的非晶软磁合金。研究发现,Mo元素微合金化能有效提高合金的非晶形成能力,1%的Mo可以将该非晶合金体系的Fe含量极限提高到84%以上,从而得到了饱和磁感应强度(Bs)高达1.63 T的非晶合金。其中Fe80Si4.75B9.5P4.75Mo1非晶合金可以铸造形成非晶块体样品,临界直径达到1mm,饱和磁感应强度达到1.54 T,矫顽力为1.9 A/m。在整个成分范围内,该合金体系都具有1.9~5.1 A/m的低矫顽力和高于传统Fe-Si-B合金的饱和磁感应强度(Bs),具有较好的应用前景。     

不锈软磁合金研究

探讨了不锈软磁合金的产生、发展和应用。提出了开发不锈软磁合金、提高磁性能和耐蚀性的设计理念和方法。推荐了磁感应强度B25,电阻率ρ与合金成分关系的经验方程式。     

Recent developments of soft magnetic alloys in Japan

Soft magnetic alloys that are now in practical use or under development in Japan are reviewed. In the field of Si-Fe alloys, the influence of various processing parameters, such as addition of elements, heat treatments, and alloy composition on the mechanical and the magnetic properties and recent developments in methods of measuring iron losses are described and discussed. As for Ni-Fe alloys, the effects of refining reagents or added elements adjusting the formation of the superlattice Ni3Fe on the magnetic properties are given. Finally systematic studies on the relation between degree of order and magnetic properties of Ni-Mn alloys are reviewed.     

Texture development in high strength aluminium alloys

Abstract

Texture development during the thermomechanical processing of high strength aluminium alloys is reviewed. The alloys dealt with include both conventional heat treatable alloys, and unconventional materials such as rapidly quenched alloys and metal-matrix composites. The processing routes considered include hot and cold rolling, extrusion, forging, recrystallisation, and superplastic deformation. The information is presented as (111) pole figures and orientation distribution functions, in order to illustrate the much greater degree of detailed information that can be extracted from the latter method of analysis. The implications of texture development are considered by examining the effects that texture can have on tensile property anisotropy and fatigue and fracture behaviour.

MST/1292     

用环形试样测定软磁材料磁各向异性的研究

采用趋近饱和定律测定了纳米晶合金环形试样有效磁各向异性常数＜K＞.为了对比测量的准确度,同时测试了传统的晶态坡莫合金环形试样的磁晶各向异性.结果表明,用环形试样可以完成对低矫顽力的软磁材料进行磁各向异性的测定.     

An automated compact vibromagnetometer for investigating soft magnetic materials

An automated vibration magnetometer for measuring the magnetization and hysteresis curves of soft magnetic materials at room temperature is described. The vibromagnetometer has a magnetic moment sensitivity of 5∙10^–6 Gs∙cm³, a measurement error of less than 3% and a magnetizing field strength range of up to ±200 Oe, which can be extended to ±10000 Oe using more powerful magnetic systems. Hysteresis characteristics of amorphous ferromagnetic microwire and of a printed text sign are presented.     

Metallographic preparation of soft materials: Lead alloys

Metallographic preparation of lead and its alloys is notoriously difficult due to the low hardness of the material and its tendency to pick up and embed abrasive particles readily. Working with component parts for lead acid batteries at Lucas Advanced Vehicle Systems Development, the odd shapes and sizes, such as connector posts and intercell welds, do not lend themselves to microtoming or electropolishing. Vibratory polishing had been used in the past but this method could take up to 6 days to produce an acceptable microsection. Using semiautomatic polishing equipment had proved more successful, but again long periods of time were taken to produce satisfatory results with all the problems of lubricant and abrasive dosing. Tests on newer, commercially available pads and abrasives provided by various manufacturers have been carried out, but it was found that a combination of machining, polishing with diamond, and final polishing with alumina gave the best results. The use of automatic polishing equipment made the preparation easier with both contrarotation and complementary rotation directions. Lubricants and abrasives recommended by the metallographic consumable suppliers for soft materials were not suitable for the easily stained and oxidized lead alloys. This report lays out the steps taken to produce the stated optimized procedure and shows some unusual structures that have been revealed in components taken from batteries undergoing testing, one of which had suffered explosive damage.     

Optimization of soft magnetic properties in nanoperm type alloys

In the present paper, it was shown that soft magnetic properties of the group of amorphous alloys Fe–X₂–B₂₂ (X=Cr, Zr and Nb) can be optimized (magnetic permeability increases about five times) by applying 1-h annealing at temperatures: 600, 600, 650 and 700 K for the Fe₇₈B₂₂, Fe₇₆Cr₂B₂₂, Fe₇₆Zr₂B₂₂ and Fe₇₆Nb₂B₂₂ alloys, respectively. This effect is attributed to annealing out of free volumes formed into material during fabrication and for the Fe₇₆Zr₂B₂₂ alloy also to a formation of a nanocrystalline phase. Using isothermal measurements of magnetization (magnetic balance), it was shown that the process of formation of nanocrysalline phase can be described by Johnson–Mhel–Avrami kinetic. Activation enthalpy of this process was deduced as 3.2 eV and the power law exponent 3.4.     

Application of Fe-P-B alloys in developing wear-resistant composite materials

Structures and properties of alloys, which belong to the Fe₃(P,B)-Fe₅PB₂-Fe₂P, Fe₂B-Fe₃(P,B)-Fe₅PB₂, Fe₂B-Fe₃(B,P)-Fe₃(P,B), and Fe-Fe₃(P,B)-Fe₃P concentration triangles of the Fe-P-B phase diagram have been studied. To produce composite materials for operation under the conditions of abrasive wear at increased temperatures, a Fe-12P-1B alloy has been recommended as a filler. The formation regularities of the structure and properties of interfaces between the Fe-12P-1B filler and copper-based binders in composite materials produced by infiltration have been defined.     

Texture mechanism in some fcc-type soft magnetic materials

The authors have studied the mechanism for recrystallization texture in some soft magnetic materials with fcc crystal structure. The alloys used were 77% Ni-14% Fe-5% Cu-4 wt% Mo permalloys. Thin foils selected area electron diffraction (SAD) and X-ray diffraction techniques were employed using a Philips 300 Electron Microscope (EM 300) and an X-ray diffractometer, respectively. Investigations were carried out on deformed, recovered and recrystallized states of the alloys. The various results show that the cold-rolled (deformed) and recovered states of the alloys possess copper-type of rolling texture with {110} 〈112〉 texture as the predominant deformation texture though other minor components such as {112} 〈111〉, {110} 〈001〉 and {123} 〈420〉 textures were detected. No cube texture, {100} 〈001〉 was detected in any of the deformed and recovered materials though the recrystallization texture in these alloys is the cube texture, {100} 〈001〉 which forms over 80% of the annealing texture in these alloys. It is concluded here that the detection of cube texture in the deformed and recovered materials is not a prerequisite for the detection of cube texture in these alloys. The present work is not conclusive about the mechanism for recrystallization texture, but it is proposed here that recrystallization texture, in these alloys is attributed to the growth-oriented mechanism based on the following model. (1) The lattice domains which form the recrystallization texture are present in the cold-rolled matrix. (2) The favoured site for nucleation are the grain boundaries and deformation band boundaries. (3) For the nucleus to be able to grow and form the recrystallization texture it must possess the necessary free energy. (4) Grains must be capable of growth into two or more orientations between which it forms, i.e. the nuclei which form the cube texture should have a [111] pole in common with the matrix in which they grow and a rotation of about 30° around this pole.     

Viscosity-based magnetodynamic model of soft magnetic materials

A time-stepping method based on the concept of magnetic viscosity developed to reproduce the excess loss in electrical steel is proposed. A numerical scheme for simultaneous solution of Maxwell equations and equations describing the magnetic viscosity has been developed. The method is suitable for describing arbitrary magnetization regimes such as waveforms associated with pulsewidth modulation (PWM) voltage excitation, and the model differential equations can be conveniently combined with equations of an external electric circuit. The accuracy of the proposed dynamic model is shown using three nonoriented electrical steel as examples. Fitting of the magnetic viscosity parameters for one sinusoidal flux regime enables dynamic hysteresis loops and losses to be predicted with high accuracy over a wide range of frequencies and amplitudes of sinusoidal or nonsinusoidal flux densities.     

Nitrogen-induced optimization of corrosion resistance for nanocrystalline soft magnetic Fe-Zr-B alloys

The poor corrosion resistance restricts the industrial applications of nanocrystalline soft magnetic Fe-Zr-B alloys.We reported a facile plasma-nitriding surface process to enhance the corrosion resistance of a nanocrystalline Fe90Zr7B3 alloy without deteriorating its soft magnetic properties.Potentiodynamic po-larization and electrochemical impedance spectroscopy were performed to investigate the corrosion be-havior.The nitrided alloy shows higher corrosion resistance than the untreated alloy,as evidenced by a nobler corrosion potential,lower corrosion current and higher polarization resistance of surface corrosion film,while their magnetic properties are similar.The microstructures of both nanocrystalline alloys were examined by high-resolution transmission electron microscopy(HRTEM)and the compositions of their corrosion films analyzed by X-ray photoelectron spectroscopy(XPS).For the nitrided alloy,a more homo-geneous nanocrystalline structure developed in the surface nitrided layer containing corrosion-resistant nitride phases(Fe3N and ZrN)provides a higher resistance against chloride corrosion.Moreover,the ni-trided layer facilitates the formation of a more protective corrosion film with the increased ratios of Fe2+/Fe3+and O2-/OH-as well as higher enrichment of Zr-and B-oxides,while the N-species(NH4+and NO3-)formed in the corrosion film behave as good corrosion inhibitors and further enhance the film pro-tection.Our findings provide a simple strategy for the preparation of corrosion-resistant nanocrystalline soft magnetic alloys to satisfy a variety of engineering requirements.     

Arc slag remelting for high strength steel & various alloys

Arc Slag Remelting (ASR) is a variant of standard ESR that accumulated advantages of ESR and VAR. Principles of ASR and it comparison with the standard ESR are given. Also discussed possibilities and limitation to replace ESR by ASR to reduce specific electric power consumption to the level of 800 kWt* hour per ton. Data full scale rectangular ASR ingot of HSLA and medium alloed steel melting are presented along with the metal quality examination. Requirements to the equipment for ASR commercialization are summarized. Also discussed area of ASR application for high alloyed steel and alloys as well as for titanium.     

A design-centered approach in developing Al-Si-based light-weight alloys with enhanced fatigue life and strength

Material heterogeneities and discontinuities such as porosity, second phase particles, and other defects at meso/micro/nano scales, determine fatigue life, strength, and fracture behavior of aluminum castings. In order to achieve better performance of these alloys, a design-centered computer-aided renovative approach is proposed. Here, the term “design-centered” is used to distinguish the new approach from the traditional trial-and-error design approach by formulating a clear objective, offering a scientific foundation, and developing a computer-aided effective tool for the alloy development. A criterion for tailoring “child” microstructure, obtained by “parent” microstructure through statistical correlation, is proposed for the fatigue design at the initial stage. A dislocations pileup model has been developed. This dislocation model, combined with an optimization analysis, provides an analytical-based solution on a small scale for silicon particles and dendrite cells to enhance both fatigue performance and strength for pore-controlled castings. It can also be used to further tailor microstructures. In addition, a conceptual damage sensitivity map for fatigue life design is proposed. In this map there are critical pore sizes, above which fatigue life is controlled by pores; otherwise it is controlled by other mechanisms such as silicon particles and dendrite cells. In the latter case, the proposed criteria and the dislocation model are the foundations of a guideline in the design-centered approach to maximize both the fatigue life and strength of Al-Si-based light-weight alloy.     

Fields in electrical devices containing soft nonlinear magnetic materials

The Colorado method for the solution of the non-linear form of Laplace's, Poisson's, and the diffusion partial differential equations is explained. Various boundary conditions can be satisfied. The transformation of the partial differential equation into a large set of finite difference equations is given. The discretization is based on a grid system consisting of two sets of orthogonal grid lines. The resulting meshes are nonuniform. Successive line overrelaxation method is used for the solution of the nonlinear equations in two steps. For the improvement of convergence, two methods of acceleration of convergence are described.     

Co-based soft magnetic bulk glassy alloys optimized for glass-forming ability and plasticity

Co-based bulk glassy alloys (BGAs) have become more and more important because of their nearly zero magnetostriction and high giant magneto-impedance effect. Here, we report the improvement of glass-forming ability (GFA), soft-magnetic properties and plasticity by a small addition of Mo atoms in CoFeBSiNbMo BGAs. (Co_0.6Fe_0.4)₆₉ B _20.8Si_5.2Nb_5?x Mo _x ferromagnetic BGA cylindrical glassy rods were fabricated successfully with a diameter of 5 mm by conventional copper mould casting method. It reveals that the substitution of a small amount of Mo for Nb makes the composition to approach a eutectic point and effectively enhances the GFA of alloy. In addition to high GFA and superhigh strength, the compressive test shows that the Mo addition can improve the plasticity for the obtained BGAs. The combination of high GFA, excellent soft-magnetic properties and good plasticity demonstrated in our alloys is promising for the future applications as functional materials.     

High performance of low cost soft magnetic materials

The consistent interest in supporting research and development of magnetic materials during the last century is revealed in their steadily increasing market. In this work, the soft magnetic nanocrystalline FINEMET alloy was prepared with commercial purity raw materials and compared for the first time with the generally studied high purity one. The exhaustive characterization covers several diverse techniques: X-ray diffraction, Mössbauer spectroscopy, differential scanning calorimetry, differential thermal analysis and magnetic properties. In addition, a brief economic analysis is presented. For the alloys annealed at 813 K, the value of the grain size was 16 nm with 19·5% of Si, the coercivity was 0·30 A m^?1 while the saturation was 1·2 T. These results prove that structural, magnetic and thermal properties of this material are very close to the expensive high purity FINEMET alloy, while a cost reduction of almost 98% seems highly attractive for laboratories and industry. The analysis should be useful not only for the production of FINEMETs, but for other type of systems with similar constitutive elements as well, including soft and hard magnetic materials.