Vol 126, No 8 (2025)

The influence of thermomagnetic treatment (TMT) including annealing and cooling of the alloy in a constant magnetic field of 10 kOe applied both along the <100> direction and across one on the magnetostriction of single-crystal samples of the Fe–18 at % Ga alloy has been studied. The samples in the form of thin disks had the “Goss” orientation of the crystallographic axes – {011}<100>. The field dependences of the longitudinal – λ100 and transverse – λ100 ⊥ magnetostriction coefficients were measured before and after TMT. By comparison with literature sources dealing with domain structure, it is shown that magnetoelastic properties correspond to the type of domain structure in alloy samples after slow cooling without external influences (before TMT) and after TMT in a magnetic field parallel or perpendicular to the easy magnetization axis [001] lying in the plane of the sample. Before and after TMT, in a field parallel to the [001] axis, there is a small longitudinal magnetostriction λ100 within a few tens of ppm, while its transverse component λ100 ⊥ is negative and reaches an absolute value of 160–190 ppm. This corresponds to a stripe domain structure, when the magnetization is predominantly oriented parallel to the [001] axis. If during TMT the magnetic field was applied perpendicular to the [001] axis and parallel to the [110] axis, then after TMT a twofold increase in the coefficient λ100 and a 40 percent decrease in λ100 ⊥ are observed. Such changes in magnetoelastic deformation indicate the formation of a transverse domain structure, the domains in which are predominantly magnetized parallel to the [100] and [010] axes. The observed TMT effects and their stability under normal conditions are explained by the directional ordering of Ga–Ga pairs in the bcc lattice of the Fe–Ga alloy.

The magnetic separation technology is used in innovative water purification methods for pollutant removal from aqueous media. The efficiency of the magnetic separation depends on the characteristics of the non-uniform magnetic fields generated by magnetic systems, the properties of the aqueous medium, and the magnetic particles.
The influence of gradient magnetic fields generated by permanent magnet assemblies on sedimentation of Fe3O4–SiO2 nanoparticles in aqueous solutions with various viscosities was studied. Numerical modeling was used to calculate the Bz and |Bz·dB/dz| values under the surfaces of a permanent magnet, radial and plane-parallel assemblies made of Sm2Co17 permanent magnets, and soft magnetic steel. It was shown the areas of high values of |Bz·dB/dz| near the surface of the magnetic systems are produced by the assemblies M1 and M2 due to their complex geometries. The magnetic sedimentation efficiency (MSE) of nanoparticles in magnetic field gradients
generated by magnetic systems was studied. The MSE in aqueous solution with a viscosity of 0.89–3.07 mPa·s after exposure time during 30 minutes in the magnetic field of the radial assembly is more than 50%. To achieve the MSE more than 50% at using a plane-parallel assembly, it is required 1 and 5 hours exposure time for aqueous
solutions with a viscosity of 0.89 and 3.07 mPa·s, respectively. The MSE of nanoparticles are higher at using of the assemblies than the permanent magnet. In the areas of high values of |Bz·dB/dz| near the surface of the assemblies the particles velocities are increased, which accelerate the settling of magnetic nanoparticles.

The magnetic impedance of wires in the low-frequency regime is theoretically considered. The vicinity of the Curie temperature and spin-orientation transitions are analyzed. It is shown that nonlinear effects are much more sensitive to changes in the magnetic field than linear impedance.

An experiment was performed on the convergence of a thick-walled cylindrical shell made of steel 20 under the action of an explosion. The explosion was initiated from eight points evenly spaced along the ring on the
cylindrical surface of the shell. It is established that convergence begins by a solid-state mechanism, with
division into eight fragments according to the number of initiation points. In the process of convergence, the solid-state mechanism is replaced by a hydrodynamic one, in which the shell converges without collapsing, through the formation of ejections (cumulative jets), their expansion and closure in the center of the shell. The change in the convergence mechanism is explained by a decrease in strength and an increase in the ductility of the steel due to an increase in the temperature of the shell during the convergence process. The study of the microstructure showed that high-speed deformation during convergence occurs with the formation of extended bands of localized shear and vortex structures.

The possibility of using the sessile drop method to determine the capillary constant and surface tension of metallic melts by measuring the parameters of the drop after its crystallization was considered. The method is quite applicable if the change in the drop's volume resulting from the phase transition is small and lies
within the error of the digital reproduction of its profile. Pure indium, tin, and lead were investigated as examples. The role of flux in the experiments was studied. A new algorithm for determining the capillary constant from the drop profile, based on the solution of the Young–Laplace equation and the Nelder–
Mead simplex optimization method, was developed and numerically implemented.

The thermal stability of thin wires made of six aluminum alloys Al–0.25%Zr, additionally alloyed with Si, Er, Hf or Nb, has been studied. Aluminum alloy workpieces were obtained by induction casting, followed by stabilizing annealing (450°C, 1 h) and severe plastic deformation to fragmentation the cast structure. The wire with a diameter of 0.3 mm was made by drawing at room temperature. The thermal stability of the mechanical properties, microhardness, and specific electrical resistivity (SER) of stabilized aluminum wires has been studied. As the annealing temperature increases, a monotonous decrease in the tensile strength, microhardness, and SER of the wires occurs. It is established that the ductility of the wires
depends nonmonotonously (with a maximum) on the annealing temperature. The results of studies of the thermal stability of the properties of stabilized wires are compared with the characteristics of wires that have not been subjected to preliminary stabilizing annealing (450°C, 1 h).

The influence of segregations on the processes of grain boundaries (GB)sliding and the energy characteristics of grain boundary shifts for asymmetric GBs of tilt Σ5{010}/{340}<001> and Σ5{110}/{710}<001>
in bicrystals of Al–Mg and Al–Ni alloys was studied using atomistic modeling methods. The energy of generalized grain boundary stacking faults was determined, and preferred directions and the energy barrier for grain boundary sliding were established. It is shown that Ni segregation-induced nano-faceting significantly modifies the grain boundary structure, increasing the slip resistance.