Том 117, № 1 (2016)

This work is devoted to the problem of extracting the contribution of the anisotropy of relaxation to the angular dependence of the FMR linewidth and to the opportunity of determining the values of the parameters of relaxation. The results of the FMR study of films based on the yttrium iron garnet prepared by the method of liquid-phase epitaxy are given. The orientational dependence of the linewidth has been calculated using the traditional method of measuring an FMR spectrum and a method based on scanning at an angle to the resonance field for obtaining the minimum linewidth. A model for calculating the linewidth has been proposed that takes into account the anisotropy of the relaxation term in the equation of motion of the magnetic moment. The model leads to a dependence that agrees well with the experimental data, which makes it possible to state that the anisotropy of relaxation most likely takes place in the samples under consideration at the temperatures employed.

In the statistical theory of the ordering of carbon atoms in the z sublattice of martensite, the most important role is played by the parameter of the strain interaction of carbon atoms λ₀, which determines the critical temperature of the bcc–bct transition. The values of this parameter (6–11 eV/atom) obtained in recent years by the methods of computer simulation differ significantly from the value λ₀ = 2.73 eV/atom obtained by A. G. Khachaturyan. In this article, we calculated the value of λ₀ by two methods based on the molecular-dynamics simulation of the ordering of carbon atoms in the lattice of martensite at temperatures of 500, 750, 900, and 1000 K in a wide range of carbon concentrations, which includes c_crit. No tails of ordering below c_crit have been revealed. It has been shown analytically that there is an inaccuracy in the Khachaturyan theory of ordering for the crystal in an elastic environment. After eliminating this inaccuracy, no tails of the order parameter appear; the tetragonality changes jumpwise from η = 0 to η_crit = 0.75 at c_crit = 2.9kT/λ₀ instead of η_crit = 0.5 and c_crit= 2.77kT/λ₀ for an isolated crystal. Upon the simulation, clustering of carbon atoms was revealed in the form of platelike pileups along {102} planes separated by flat regions where no carbon atoms were present. The influence of short-range order in the arrangement of neighboring carbon atoms on the thermodynamics of ordering is discussed.

Results of measurements of thermophysical properties and thermodynamic functions of the AMg2 alloy doped with cerium determined in the regime of cooling are brought out.

Methods of optical metallography and scanning and transmission electron microscopy were used to investigate the structure of low-carbon steels of martensitic classes VKS-7 and VKS-10 subjected to warm rolling or upsetting at temperatures of 600 and 700°C (in the α state) and 800°C (in the γ state). It has been shown that the deformation by rolling at 600°C to degrees of 40 and 60% does not lead to the destruction of the lath structure of the initial martensite; an increase in the rolling temperature to 700°C and of the degree of deformation to 80% favors the development of recrystallization in situ. It has been found that, upon warm deformation by upsetting, recrystallization occurs at lower temperatures than in the case of the warm rolling. It has been shown that warm deformation by upsetting at a temperature of 700°C leads to the formation of a fragmented structure with a high fraction of ultrafine grains with a size less than 2 μm.

Changes in the structure and mechanical properties of the low-alloy chromium–zirconium bronze Cu–0.14% Cr–0.04% Zr have been investigated after a high-strain-rate (10⁴–10⁵ s^–1) deformation by the method of dynamic channel-angular pressing (DCAP) and following annealings at 300–700°C. A significant increase in the mechanical properties of the investigated bronze after DCAP and after DCAP and subsequent aging at temperatures of 400–450°C has been established. Thus, compared to the initial quenched state the ultimate tensile strength increases by a factor of 2.6 and 2.8 and the yield stress, by a factor of 3.3 and 5.1, respectively, with the retention of satisfactory plasticity. It has been shown that, upon DCAP and subsequent annealings, in the low-alloyed bronze under investigation there occurs a decomposition of the α solid solution with the precipitation of nanosized particles. This leads to a significant strengthening of the bronze and to an increase in its thermal stability compared with the pure copper subjected to DCAP.

The effect of hydrogen, accumulation and annealing of radiation defects on the physicomechanical properties of an austenitic Kh16N15M3T1 steel (16Cr15Ni3Mo1Ti) has been investigated upon low-temperature (77 K) neutron and electron irradiations. It has been shown that, when its concentration is about 300 at ppm, hydrogen reduces plasticity by 25%. The presence of helium (2.0–2.5 at ppm) introduced by the tritium-trick method exerts an effect on the yield strength and hardly affects embrittlement. Upon both electron and neutron irradiation, there is a linear relation between the increment of the yield strength and the square root of the increment of the residual electrical resistivity (the concentration of radiation defects). The annealing of vacancies occurs in the neighborhood of 300 K (energy for vacancy migration is 1.0–1.0 eV). Vacancy clusters dissociate near 480 K (energy for dissociation is 1.4–1.5 eV).