Fizika metallov i metallovedenie

The article presents experimental data on the structure and magnetic properties of films of the Gd–Co system with a low Co content (up to 20 at%) obtained by magnetron sputtering. It was found that the films of pure Gd differ in structural heterogeneity, expressed in the presence of crystalline hcp and fcc phases and presumably an X-ray amorphous phase with a large dispersion in the size of nanocrystallites. The ferromagnetism of the crystalline state and the metabolic frustration of the nanocrystalline phase ensure the asperomagnetic state of the films. Amorphization, which increases with an increase in the Co content, leads to the formation of a more homogeneous distribution of Gd atoms in the medium and provides a gradual transition to a ferromagnetic state, but with a reduced Curie temperature.

The article describes a new method for selectively applying structural barriers to the surface of samples of anisotropic electrical steel of nuclear power plants in order to crush its domain structure to reduce its total magnetic losses due to magnetization reversal. The use of selective treatment of nuclear power plant areas with a maximum value of magnetic permeability when the working tool is exposed to ultrasound has made it possible to reduce the total magnetic losses of processed samples by 10–15% with minimal damage to their magnetically active coating. This will lead to an increase in the corrosion resistance of nuclear power plants used for the manufacture of magnetic cores of transformers for various purposes.

The formation of grain boundary segregations in the equiatomic high-entropy alloy (HEA) CoNiCrFeMn upon annealing at moderate temperatures was studied using atomistic MD/MC simulation. It has been established that at the early stage of annealing, regardless of the type of grain boundaries (GBs), two types of regions with chemical short-range order Ni–Mn–Cr and Fe–Co are formed in the volume of grains. With increasing annealing time, a pronounced tendency to the formation of unusually wide segregations on the GB is observed. The main element enriching the grain size is Cr, and Fe–Co clusters are displaced to the center of the grain. The influence of GB on the redistribution of alloy components and the phase stability of HEA is discussed.

In the present work, the effect of thermal aging on the nanostructure of three oxide dispersion-strengthened steels with different alloying systems: Eurofer ODS, 10Cr ODS and KP-3 ODS was investigated by atom probe tomography. The investigated steels were aged at 650°C for 500 and 1000 h. Nanoscale clusters enriched in Y, O and Cr, as well as in V, Ti and Al depending on the alloying system of the steel were found in all states. Investigation of the changes in the nanostructure of steels after thermal aging for 500 h showed a significant increase in the number density of clusters in all steels, while after 1000 h aging their number density decreased in Eurofer ODS and 10Cr ODS, or remained at the same level in KP-3 ODS. At 500 h, the retention (10Cr ODS, KP-3 ODS) or increase (Eurofer ODS) of the average cluster size was also observed, while at 1000 h the average size was stable in Eurofer ODS and 10Cr ODS, or experienced a slight decrease in KP-3 ODS. Analysis of the nanostructure change showed first an increase in the number density of clusters (while maintaining or increasing the average size) in all steels during aging up to 500 h, corresponding to the nucleation stage of new clusters. After aging for 1000 h, a decrease in number density was found, corresponding to the maturation stage. These tendencies are also confirmed by analyzing the changes in the concentration of chemical elements in the matrix.

The structural evolution and hardness of vanadium under high pressure torsion at room temperature is investigated. Strain localization has been observed at true strains less than 1 (e < 1), leading to the formation of a banded structure. The study shows that strain localization delays the transition to the SMC structure during subsequent deformation. The mechanisms underlying the formation of deformation bands in vanadium are discussed. Dislocations are found to play a dominant role in the hardening of vanadium during the initial deformation stages (e < 1), while high-angle grain boundaries of deformation origin emerged as the main contributors at higher strains. In addition, the parameters of the Hall–Petch-type equation are determined.

Microstructural studies of samples made from various sections of fuel element shells were carried out after irradiation in the low enrichment zone of a fast neutron reactor with a sodium coolant to damaging doses of over 100 dpa. The porosity characteristics of samples irradiated with different rates of generation of atomic displacements selected from sites with different irradiation temperatures are studied. Histograms of the void size distribution are constructed for each sample, which are described by unimodal lognormal distributions. Three types of voids were identified: “small”,“medium-sized” and “large”,and changes in the average size and concentration of voids of each type were traced depending on the irradiation temperature and the rate of generation of atomic displacements.

The effect of aeroacoustic treatment (AAT) on the mechanical and technological properties of titanium VT1-0 is investigated. The dependence of the strength and ductility characteristics on the type of preliminary titanium treatments has been established: annealing, AAT and only AAT before plastic deformation significantly reduce the value of σ_B and increase plasticity, which reduces deformation forces, increases the deformation rate.The effect of pre-treatment on the process of plastic deformation of VT1-0 (a decrease in strength by ~ 200 MPa) is similar in terms of the effect of the electroplastic effect (EPE) on the strength of the wire from VT1-0.