Effect of crystallization annealing on the dynamic magnetoelastic properties of the Fe<Subscript>73.7</Subscript>Cu<Subscript>1.0</Subscript>Nb<Subscript>3.2</Subscript>Si<Subscript>12.7</Subscript>B<Subscript>9.4</Subscript> amorphous alloy

Double electromagnetic acoustic transformation method was used to study dynamic magnetoelastic properties of the Fe_73.7Cu_1.0Nb_3.2Si_12.7B_9.4 amorphous alloy subjected to crystallization annealing at different temperatures. Anomalous variations in the differential magnetostriction and ultrasound damping and velocity were found. According to Mössbauer spectroscopy data, they are related to the formation of a component of magnetic moments that is perpendicular to the ribbon surface.     

Numerical simulation of the interaction of dust particles of a comet with a spacecraft

The paper deals with the physical and mathematical statement of problems that arise in estimating the safety of the shield design of the Vega spacecraft, which was chosen preliminarily under the guidance of R. Z. Sagdeev. Numerical results for failure of shields impacted by particles of the dusty atmosphere of Halley's comet are presented. The size of the failure zones in the shields are determined as a function of the particle size and density. The probability of an impact on the second shield of the particles penetrating the shield or resulting in spalling of solid fragments is estimated. The momentum transmitted by the particle flux to the solar batteries of the spacecraft is determined.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 2, pp. 117–123, March–April, 1996.     

Structure of the Fe100−x Alx alloys (25 < x < 35 at. %) annealed in a temperature range of 400–800°C and the effect of the ordering type on the magnetic properties

X-ray diffraction was used to determine temperature ranges of annealings that allow the stabilization of the D0₃ and B2 superstructures in Fe-Al alloys at room temperature upon cooling them at a given rate. A substantial effect of the long-range-order type on the magnetic properties, such as the magnetic-ordering temperature, average magnetic moment per Fe atom, average hyperfine magnetic field at ⁵⁷Fe nucleus, and coercive force, is demonstrated using the Fe₇₀Al₃₀ alloy as an example.     

Mössbauer and magnetometric studies of uncommon magnetic properties of ordered (B2 type) Fe-Al alloys

This work presents experimental data on the Mössbauer and magnetic measurements of ordered Fe_65.9Al_34.1 (B2 type) alloy depending on temperature and external magnetic field. The results obtained show that the ground magnetic state of the alloy cannot be referred to any of the known types of magnetic ordering. A model of local magnetic moments is proposed, in which the amplitude and the sign of a local magnetic moment are determined by its local chemical surroundings. The model suggests the existence of local magnetic moments that are antiparallel to the total magnetization of the alloy: the magnetic moment of a Fe atom with five and more Al atoms in the nearest surroundings is antiparallel to the total magnetization. Within the framework of the model proposed, a quantitative agreement of the calculated and experimental values of the average magnetic moment of the Fe atom in the alloy has been obtained. It is shown that in the B2 superstructure there appear magnetic inhomogeneities of a nanometer scale, which consist of magnetic moments that are parallel and antiparallel to the total magnetization. The behavior of the magnetic and Mössbauer parameters depending on the temperature and the applied magnetic field indicates the existence of collective fluctuations of magnetic moments. The quantity of Fe atoms in such fluctuating ensembles, as evaluated from the data on the magnetization, is compared with their quantity in the magnetic inhomogeneities.     

Improving standard requirements for the quality of welded joints in steel structures ‐ part 3

The design of a flexible current conductor which greatly reduces the consumption of electric energy on the external and internal contacts of the conductor in high-power electrical systems, capable of operation at temperatures up to 500°C, is proposed. A method of manufacture of the flexible current conductor is described. The method is based on local explosion welding of a packet assembled from flexible metallic strips at the ends with the formation of a high-quality joint between the flyer plate and the unlimited number of flexible metallic strips and welding the ends of every preceding strip followed by welding the flyer plate on the area larger than the cross-sectional area of the strips.     

Structural-Phase Composition and Corrosion Behavior of Finely Dispersed Fe-C Powders in Neutral Media

Effects of the structural-phase state and the structure of the surface layer on the corrosion behavior of mechanically activated finely dispersed Fe-C powders were studied. The powders prepared by mechanical milling of iron in graphite or heptane were mixtures of phases (nanocrystalline α-Fe + amorphous Fe-C phase (AP), α-Fe + Fe₃C, and α-Fe + graphite) in different ratios. Corrosion tests were carried out in a model medium (0.85% NaCl) at 37°C. The oxide surface layer of powders containing a high content of AP was found to exhibit protective properties. The corrosion behavior of the powders is insensitive to such changes in the structural-phase state as the formation of carbides, graphite encapsulation, grain size alterations, and hydrogenation. __________ Translated from Zashchita Metallov, Vol. 41, No. 5, 2005, pp. 501–507. Original Russian Text Copyright ? 2005 by Lomayeva, Bokhonov, Syugaev, Elsukov, Reshetnikov.     

Temperature and field behavior of magnetic properties of ordered alloys Fe100?xAlx (25 < x < 35 at %)

Results of M?ssbauer and magnetic studies of partially ordered alloys Fe_{100 − x} Al _x (25 < x < 35 at %) are discussed depending on the temperature and applied magnetic field. Two variants of the interpretation of the temperature behavior of magnetization and average hyperfine magnetic field at ⁵⁷Fe nuclei in the model of a collinear magnet with magnetic inhomogeneities of a nanometer range are suggested. In the first variant, the existence of clusters with magnetic moments oriented parallel and antiparallel to the total magnetization is assumed. Temperature anomalies, such as the nonmonotonic dependence of magnetization and hyperfine magnetic field in the temperature range of 100–200 K, are explained at a qualitative level by the stabilization of relaxation phenomena in clusters due to Stoner-type spin excitations. The second variant is based on the assumption of a change in the orientation of spins antiparallel to the magnetization with increasing temperature.     

Structural state and magnetic properties of cementite alloyed with manganese

Using X-ray diffraction analysis, M?ssbauer spectroscopy, and magnetic measurements, the structure, parameters of hyperfine interactions, localization of Mn atoms in the lattice, coercive force, and specific saturation magnetization have been investigated in the mechanically alloyed and annealed cementite (alloyed with manganese) of compositions (Fe_{1 ? x} Mn _x )₃C (x = 0?C0.12). It has been shown that strongly deformed cementite resides in the low-coercivity state and, after annealing in the vicinity of 500°C, in the high-coercivity state. Alloying with manganese reduces the coercive force, the specific saturation magnetization, and the Curie temperature of cementite. Inhomogeneities of the distribution of manganese atoms indicate the temperature dependence of the coercive force of mechanically alloyed and annealed cementite samples.     

Effect of Structural-Phase Composition on Magnetic Properties of Iron Powders Ground in Carbonaceous Medium Doped with Surface-Active Substance

In the process of intense grinding of iron powders in heptane with addition of oleic acid, the particles' dimensions reduce, their shapes change, and the particles are saturated with carbon, oxygen, and hydrogen atoms, which diffuse to the regions of mosaic block boundaries and form weakly ordered clusters and iron-based phases. The coercive force increases from 8.5 to 92 A/cm as a result of grinding. In the process of anneal, ordered phases Fe₃C and Fe₃O₄ are produced from disordered clusters and phases, which leads to an increase in the coercive force to 220 A/cm.     

Fabrication of Mixed Urianium–Plutonium Fuel on the Paket Setup and Waste Handling Methods

The results of fabrication of fuel elements with mixed uranium–plutonium oxide fuel are presented. The experimental fuel assemblies assembled from the fuel elements were tested in BN-350 and -600 reactors. Postreactor investigations of the fuel elements showed that there was no substantial difference in the behavior of the fuel cores consisting of the mixed fuel as compared with UO₂ fuel. Solid and liquid radioactive wastes are produced during the fuel fabrication process. A classification of the wastes and methods for handling them is given. It is shown that the off-grade sintered pellets should be pulverized and returned to the beginning of the mixed-fuel fabrication process.