卷 117, 编号 10 (2016)

Some specific features of the reconstruction of the domain structure of thin (0.10 mm) Fe–3% Si single crystals have been investigated depending on the frequency of the magnetization reversal in rotating magnetic fields. The studies have been carried out in the range of frequencies of 60–300 Hz and induction amplitudes of 0.5–1.6 T. It has been established that the magnetization reversal of the samples of this thickness occurs via the displacements of 180° domain walls of the stripe domain structure without the participation of the C-domain walls. A qualitative explanation to the revealed features of the behavior of the domain structure has been given, and their possible contribution to the magnetic losses of the investigated samples has been evaluated.

The influence of heat treatment in air on the level of magnetic properties has been studied on the example of a ribbon of an amorphous cobalt-based (Co–Fe–Ni–Cr–Si–B) soft-magnetic alloy with a nearzero saturation magnetostriction. The investigation of the interaction of the ribbon surface with water and water vapor and its influence on the magnetization distribution showed the possibility of applying surface treatment to determine the sign of saturation magnetostriction. The sign of saturation magnetostriction in the initial (quenched) state confirmed the presence of a negative magnetostriction in the ribbon. Based on the results obtained, the dependence of the sign of saturation magnetostriction on the structural state that is obtained upon heat treatment has been revealed.

The preparation and analysis of gradient nanostructured coatings obtained by the method of the magnetron sputtering of a multiphase composite AlN–TiB₂–TiSi₂ target are described. The structure and phase and elemental compositions have been investigated by the methods of X-ray diffraction (XRD), atomic force microscopy (AFM), and electron microscopy (SEM and TEM, with energy-dispersive analysis). The mechanical properties of coatings were characterized by the method of nanoindentation. The coating formed consisted of three layers different in the elemental composition and structure, which determined its mechanical properties. The formation of structurally inhomogeneous coating is explained by the fact that the target to be sputtered consisted of three different components (AlN, 50 wt %; TiB₂, 35 wt %; TiSi₂, 15 wt %) inhomogeneously distributed over the volume of the target. The influence of different processes that occur upon the sputtering of multiphase targets by ions of inert gases on the formation of nanocomposite coatings with a gradient structure is discussed.

Data are given concerning the opportunity of applying barocryodeformation (plastic deformation under the conditions of severe uniform compression at cryogenic temperatures) to produce ultrafine-disperse martensitic structure in Kh18N10T steel (≤0.08 C, 18 Cr, 10 Ni, <0.7 Ti, ≤2 Mn, ≤0.8 Si (wt %)), which ensures an increase in the physicomechanical characteristics of material that are unattainable when using other types of treatment. Experiments are described that make it possible to explain the high (in spite of the presence of large forces of uniform compression) rate of completion of the martensitic transition upon the deformation of the steel under such conditions.

The structure and morphology of Nb₃Sn superconducting layers that are formed in multifilamentary conductors with distributed tin sources in different diffusion-annealing regimes have been investigated by transmission and scanning electron microscopy. The composites studied differ in the design (the number of Nb filaments and their final diameter, initial tin concentration, the presence of reinforcing Cu‒Nb inserts in the stabilizing copper sheath, alloying of the copper matrix with manganese) and diffusion-annealing regime. In all of the conductors, superconducting layers arise with zones of different morphologies, namely, columnar grains are present along with fine equiaxed Nb₃Sn grains. Compared to Nb₃Sn-based conductors produced by the so-called bronze method, composites with internal tin layers are characterized by coarser Nb₃Sn grains with a greater spread of sizes. Nevertheless, the critical current density J_c of these latter can reach values 2276 A/mm² due to a higher Sn concentration in the superconducting phase and a larger relative amount of this phase in the conductor. Lower values of the critical current density (J_c = 850 А/mm²) were obtained in the conductor with a reduced tin concentration in the matrix and an enhanced number of Nb filaments with a smaller diameter, in which coarser Nb₃Sn grains with a wide spread of sizes and wider zones of columnar grains are formed.

The effect of heat and thermomechanical treatments conditions on the microstructure and main mechanical characteristics (obtained by tensile, high-temperature long-term strength, fracture toughness, and high-cycle fatigue tests) of the Ti–45Al–5Nb–1Mo–0.2B (аt %) alloy was studied. Before the treatments, the sequence of phase transformations in the alloy after its solidification was determined by testquenching method. The obtained data were used to develop conditions for the heat and thermomechanical treatments. It was found that a small but stable increase in the plasticity and strength of the cast alloy is observed after three-stage annealing at temperatures that correspond to the (α + γ)- and (α₂ + β(В₂) + γ)-phase region. The thermomechanical treatment at temperatures corresponding to the (α(α₂) + β(В₂) + γ)-phase region and subsequent two-stage annealing at temperatures that correspond to the (α + β(В₂) + γ)- and (α₂ + β(В₂) + γ)-phase region lead to the formation of fine-grained duplex structure. This determined the substantial improvement of the low-temperature plasticity and strength (δ = 3.1% and σ_u = 860 MPa at 20°C, respectively) and retained high creep resistance to 700°C.

Composite materials based on alloys of the Al–Si–Mg system have been obtained via the introduction of 5, 10, and 15 wt % of SiC particles into the alloy melt and the solidification under a pressure. As a result of solidification under pressure, the porosity of the composite materials decreased substantially. An increase in the content of SiC particles in the composites enabled a smaller size of dendritic cells to be obtained. It has been shown by the X-ray diffraction method that, in the process of solidification under pressure, an interaction occurred between the matrix and reinforcing SiC particles. The presence of SiC particles in the structure of composites led to the acceleration of the aging process and to an increase in the peak hardness in comparison with the matrix alloy.

The structure and mechanical properties of ultra-low carbon interstitial-free (IF) steel in the annealed state, after warm and cold rolling, and as a component of seven-layer steel–aluminum composite have been studied. A comparative analysis of the results of structural studies using optical microscopy and scanning and transmission electron microscopy have revealed the possibility of the formation of an ultrafinegrained structure in a steel layer during rolling at temperatures ranging from room temperature to 520°C. It has been found that the seven-layer composite has higher strength properties as compared to monolithic samples of the IF steel after analogous regime of the warm rolling.