Vol 117, No 6 (2016)

In this paper, we have studied the effects of the thermomagnetic treatment in a transverse magnetic field (TMaT_⊥) on the permeability of the amorphous alloy Co₆₉Fe_3.7Cr_3.8Si_12.5B₁₁ with such a low saturation magnetostriction (λ_s 10^–7) that, in the ribbons of this alloy rolled into a toroid, a sharp longitudinal magnetic texture is observed (K_sq > 0.90). It has been revealed that the permeability μ₄ (H = 4 mOe, f = 1 kHz) as a function of the annealing temperature or time of holding at a temperature is described by a curve with a maximum. This maximum is observed at a coefficient of the squareness of the hysteresis loop K_sq,m in the range of 0.2 ≤ K_sq,m ≤ 0.4. The regimes of the TMaT have been determined that provide optimum values of the permeability μ₄ (15000) without a loss of the ductile state of the ribbons of this alloy. Based on the example of an iron-based alloy of composition Fe₅₇Co₃₁Si_2.9B_9.1 with λ_s = 35 × 10^–6, it has been shown that the formation of the hysteretic magnetic properties upon the TMaT_⊥ depends substantially on the magnitude of the magnetostriction and the Curie temperature of the amorphous alloys.

Methods of optical, atomic-force, and transmission and scanning electron microscopy, as well as X-ray diffraction analysis have been used to study the effect of electron-beam treatment on the surface morphology and structure of titanium of grade VT1-0. It has been shown that irradiation by three electron pulses with an energy density in the beam of W = 12–24 J/cm² and a pulse duration of 50 μs leads to the formation of VT1-0 samples of a multilayer structure in the surface layers that consist of fine particles of the α phase, which have a subgrain structure, and of the underlying coarse grains, which contain α’ martensitic phase. The influence of the density of energy of the electron beam on the hardness and the magnitude of microand macrostresses that develop in the modified surface layer has been demonstrated. The results of calculating the thermal fields that appear in the process of treatment by electron beam are presented.

The structure and kinetics of the formation of austenite in medium-carbon steel during shortterm heating above the temperature Ac₁ followed by accelerated cooling are analyzed. It has been shown that the abnormal formation of pearlite in steel results from the concentrational and structural inhomogeneity of austenite, as well as the presence of carbide particles in ferrite areas.

The structure and mechanical properties of pearlitic steels, which contain ~0.6% carbon and copper in the amount of 1.25 and 1.4%, have been studied in the states immediately after the pearlitic transformation (with different rates of cooling) and after tempering at 500°C. It has been established that tempered pearlitic steel with copper is 10–15% stronger than the steel of similar composition without copper. The strengthening of copper-containing pearlitic steel after tempering is caused by the precipitation of copper particles 5–20 nm in size in the ferritic regions of pearlite and in grains of free ferrite.

The structure, composition, and properties of transition-metal diboride films have been studied. It was shown that they are characterized by a wide range of structural states, namely from amorphous-like to nanocrystalline with crystallite sizes of 1–50 nm. The characteristic peculiarity of the structure of film transition-metal diborides with high physical and mechanical properties is the formation of a nanocrystalline (columnar) structure with the growth texture in plane [00.1] and a nanocrystallite size of 20–50 nm. The element composition of a superhard highly textured film transition-metal diborides was studied by ion mass spectrometry and Auger electron spectroscopy. The overstoichiometry effect in nanocrystalline transitionmetal diboride films is explained. It was shown that this effect is related to the formation of an additional B⎯B covalent bond, which is realized at subgrain boundaries and leads to the appearance of superhardness in the formed coatings.

The phase composition and the characteristics of vacancy voids in cold-worked steel 07C–16Cr–19Ni–2Mo–2Mn–Ti–Si–V–P–B (CW EK164-ID) after neutron irradiation at damaging doses of 36–94 dpa and temperatures of 440–600°C are investigated. In the entire range of damaging doses and temperatures, voids with different sizes are observed in the material. The maximum void size increases with irradiation temperature up to ~550°C, whereas their concentration decreases. At higher irradiation temperatures, almost no coarse voids are observed. The concentration of fine voids (to 10 nm in size) sharply increases with temperature from 440 to 480°C. Further increases in the temperature do not result in the noticeable concentration growth. In the irradiation temperature range of 440–515°C, second phases precipitate (G phase, γ’ phase, and complex fcc carbides). At higher irradiation temperatures, there are Laves-phase particles, fine second carbides of the MC type, and needle shape precipitates identified as phosphides in the material.

Structure has been studied and the distribution of the filler in the samples of the metal-matrix Al/SiC composite containing 50% SiC has been analyzed. The sizes and shapes of the particles of the filler have been determined; the cohesion of the metallic matrix with the filler has been investigated. The analysis of the mechanism of fracture after tensile tests at 350°C and uniaxial compression of the samples of composite at 300 and 600°C has been carried out.