Papers by Keyword: Amorphous Alloy

Abstract: The glass forming ability and magnetic properties were investigated for adding neodymium to the Fe_71-xNb₄B₂₅Nd_x (x=0, 3, 5, 7,10) alloys prepared by copper suction casting. It was found that proper neodymium (x=5~10 at.%) could improve glass forming ability of Fe-Nb-B alloys effectively. Bulk amorphous Fe₆₆Nd₅B₂₅Nb₄ and Fe₆₄Nd₇B₂₅Nb₄ samples were obtained and presented high thermal stability and good soft magnetic properties. The value of activation energy of the first crystallization peak for the bulk amorphous alloy Fe₆₄Nd₇B₂₅Nb₄ is 683 kJ/mol.

Abstract: In-suit β-Ti (Zr,Nb) dendrite/amorphous matrix composites were prepared by copper injection casting, specimens (1.5:1 aspect ratio) with different diameters were tested under quasi-static compressive loading at different strain rate. The results show that the structure of amorphous composites is amorphous matrix and in-suit β dendritic crystal phase; for 3mm and 4mm specimens, with the change of strain rate, the compressive strength and the fracture strain have no obvious changes. however, positive strain rate sensitivity was observed to 5mm specimens; in the same strain rate, with the decrease of the diameters, compressive strength and fracture strain all have great increases, which indicate the amorphous composites has obvious size effect.

Abstract: Mechanical alloying (MA) is used to prepare amorphous alloy powders. The experiments were performed by a high energy ball milling device using stainless steel vessels and balls under argon atmosphere at a rotation rate of 450 r/min. B and Y were used as the minor additions to prepare new quaternary or complex amorphous alloy powders. Ti₅₀Al_(47-x-y)Zr₃B_xY_y (x=0, 0.6, y=0, 0.2) amorphous alloy powders were successively obtained. The milled amorphous alloy powders were characterized by XRD, SEM and DSC. Ti₅₀Al₄₇Zr₃ amorphous alloy powders were obtained after milled 50h. The milling time needed to obtain complete amorphous alloy for Ti₅₀Al_46.4Zr₃B_0.6, Ti₅₀Al_46.8Zr₃Y_0.2 and Ti₅₀Al_46.2Zr₃ B_0.6Y_0.2 are 40h, 35h and 30h, respectively. Minor additions of B and Y decreases the milling time for preparing amorphous alloy. SEM shows that B and Y can refine the grain of the amorphous alloy powders. DSC shows that minor substitution of 0.6at.%B or 0.2at.%Y can increase the glass forming ability (GFA) for the TiAl based alloys.

Abstract: Structural and chemical attributes of amorphous and nanocrystalline metals, which affect their corrosion behaviour are outlined. Effects of the fraction of intercrystalline regions, diffusivity, chemical homogeneity / heterogeneity and local ordering are indicated. These features can lead to higher or lower corrosion resistance as compared to coarse-grained counterparts, depending on the nature of tested metal and corrosive environment. Contributions of these factors are represented by two examples of passive behavior of nanocrystalline metals and amorphous Ni-P alloys.

Abstract: In the present work, a detailed study of the structural relaxation through the complex inductance response by using Inductance Spectroscopy (IS) of Fe-based amorphous ribbons obtained by as quenching ultra-rapid technique, as a function of frequency form 4 to 400 kHz and under thermal treatment during 10, 20, 40, 60, 120 and 180 min, is presented. The analysis of experimental results of IS plots of real (L ́) and imaginary (L ́ ́) inductance show evidence of magnetization processes associated with domain walls: At low fields and low frequencies, L ́ showed a plateau, followed by a dispersion with a relaxation character, the relaxation frequency is about 100 kHz (domain wall bulging). For higher fields, the inductance value depended on the field amplitude (domain wall displacement). As the frequency increased, all the curves merged into the low field plot and exhibited the same relaxation dispersion. The dependence of magnetization processes on the domain wall is determined and interpreted on the basis of the domain wall motion equation. In this way the structural relaxation associated with domain dynamic is discussed and we can establish criteria for the design of certain filters at low frequencies (from 4 to 50 kHz).

Abstract: The thermal properties of amorphous Ti-50at.%Pt alloy produced by mechanical alloying were studied by differential scanning calorimetry (DSC). The powders, sampled at various time periods during the milling process, displayed non-reversible exothermic reactions in the temperature range of 641-668 °C, and in the higher temperature range of 839-970 °C. The reaction peak temperatures and heat effects vary with milling time. The reactions at the lower temperature range were determined by X-ray diffraction analysis of the powder, heated beyond the onset temperature of the exothermic peaks, to be crystallisation into B19 TiPt. The reactions at higher temperatures are suspected twinning transformation of the B19 grains to form martensite. This requires confirmation by analysis with a transmission electron microscope, planned as part of future work.

Abstract: Several amorphous alloys (Ni-Fe-B) were synthesized using liquid phase reduction method. The influences of molar ratios n(Fe)/n(Fe+Ni) and different temperatures on phase composition, morphology and catalytic activity were investigated. The resulting products were characterized by XRD and TEM methods, and the catalytic activities were also evaluated by way of hydrogen release ability of NaBH₄ hydrolysis. The results show that the products have stable amorphous phase structures. With the increase of n(Fe)/n(Fe+Ni), the crystallizing tendency rises and the agglomeration strengthens. Under the conditions (T=333K, n(Fe)/n(Fe+Ni)=0.5), the as-prepared samples exhibit the highest catalytic activity, and the highest hydrogen generation rate is 1.70 mL/min^-1.

Abstract: Firstly, this paper introduces the development of new materials, new technology and new manufacture in power industry of China, energy-saving, low noise and smart distribution transformers are widely used in countryside power grid reconstruction. In this paper, application status and development trend of different types of distribution transformers were introduced and compared in terms of new material and new structure, such as oil-immersed distribution transformer, amorphous core transformer(AMT), dry-type transformer, SF6 insulated distribution transformer, composite transformer and other types of distribution transformers. The development of distribution transformer is mainly based on energy saving, miniaturization, wound core and amorphous alloy nowadays, but the class-H dry-type transformer and tridimensional toroidal-core amorphous alloy transformer are the future direction of development. The technology application of smart distribution grid, power electronics technology and dynamic reactive power compensation technique will also affect the safety and economic operation of distribution transformer.

Abstract: In this paper the change of electrical resistivity of the amorphous alloy Fe₈₀Ni₁₀Si₅B₅ during heat treatment is investigated. Parallel studies by magnetometry technique, X-ray diffraction and calorimetric analysis were used to interpret the nature of the changes in the structure and properties of the alloy during annealing. These features are related with magnetic nature of the alloy and crystallization at a higher temperature.

Abstract: Amorphous alloys have many superior properties such as high tensile strength,anticorrosion and easy soft-magnetism, but few amorphous alloys have been used as final productsbecause they lack plasticity at room temperature. Thus, we have developed a new amorphous alloyrolling method. Although the amorphous alloy was brittle at room temperature, it has deformedplastically by semisolid rolling under hydraulic stress. After being subjected to ultrarapidcooling-thermal spraying, amorphous alloy strips were rolled with a ditch roll in the viscoelasticregion below the glass transition temperature. Using this rolling method, we successfully preformedstrips for use in fuel cell separator. This rolling technique is based on the principle of stress-inducedstructural relaxation under hydraulic stress.