Том 125, № 11 (2024)

Metastable disperse states arising from decomposition in alloys are of considerable interest and have an important practice-related significance, providing high strength properties. Recently, the stabilization mechanism of disperse states through the formation of a shell enriched in alloying elements has attracted special attention. The paper presents a concise overview of the theoretical concepts pertaining to the formation and stabilization of disperse states in alloys, along with recent findings from first-principles atomistic simulations of Al–Cu–X, Fe–Cu–X, and Al–Sc–Zr alloys, wherein precipitates with a core–shell structure have been observed. Furthermore, the paper addresses the conditions of kinetic and thermodynamic stabilization of precipitates in relation to coalescence processes during annealing.

The effect of friction stir processing and subsequent aging on the microstructure and physicomechanical properties of the thermally hardened Cu–0.3% Cr–0.5% Zr alloy has been studied. Plastic deformation under friction stir processing leads to the formation of an ultrafinely grained structure with an average grain size of 0.5 μm, the decomposition of a supersaturated solid solution, and the precipitation of disperse particles in the stir zone. It has been shown that aging is accompanied by the additional precipitation of disperse particles and the development of recovery in the zone of processing. The refinement of a granular structure and the precipitation of particles leads to an increase in the strength properties and electrical conductivity in the stir zone. Aging is accompanied by a surplus increase in conductivity without any significant decrease in strength characteristics. The effect of structural evolution under friction stir processing and aging on the Cu–Cr–Zr alloy properties is discussed.

A brief review of theoretical models describing the dislocation mechanisms of misfit stress relaxation in crystalline nanoheterostructures of lower dimension, such as composite nanoparticles, nanowires, and nanolayers is presented. The critical conditions for the appearance of the first misfit dislocations in such nanoheterostructures are determined. The equilibrium distribution density was calculated for the circular prismatic loops of misfit dislocations in core–shell nanowires and proved to be in good agreement with the results of experimental observations. Energy barriers have been found for the nucleation of misfit dislocations in composite nanowires with a core shaped as a rectangular prism and in composite nanolayers with long prismatic inclusions. The lowest barriers are shown to occur upon the emission of partial or perfect dislocation dipoles by the edges of inclusions, depending on the characteristic dimensions of a heterostructure. The directions of further studies in this area were proposed.

The selection and verification of interatomic interaction models for molecular dynamics simulation of crystallization from a melt is carried out in relation to binary systems with a significant difference in solidus and liquidus temperatures, using the example of Cu–Ni and Mo–Ni alloys. The potentials used were verified based on thermodynamic calculations of equilibrium melting parameters and on available experimental data. The conditions for the formation, characteristics, and features of the evolution of the crystal structure in the course of solidification of binary systems and alloys with a significant difference in the solidus and liquidus temperatures are determined. Large-scale atomistic calculations of the redistribution of components of a Mo–Ni binary alloy in the course of its crystallization from a melt were carried out.

One of the most promising applications of high-entropy alloys (HEAs) is their use as materials for strain gauges. In order to study HEAs in the context of this application, it is necessary to be able to accurately and rapidly measure gauge factor (GF). This paper reports the results of testing and validation of a precision automated system for direct strain gauge testing of metal alloys. The technique has been applied in studies of both known strain-gauge alloys and new HEAs such as TiHfZrTa, TiHfNbTaZr, TiHfNbTa, and TiHfNbZr. It has been demonstrated that the HEAs under investigation display a markedly elevated GF with values ranging from 3.60 to 5.17. This is significantly higher than that observed in conventional materials employed in the fabrication of strain gauges, such as manganin, constantan, and nichrome. Furthermore, the examined HEAs demonstrate a considerable elastic limit, reaching up to 972 MPa. The analysis of the obtained data leads to the hypothesis that the anisotropy of the elastic properties of the material is an essential factor responsible for the high GF.

The paper presents the results of study of the magnetic structure of nonequilibrium gold–cobalt alloys obtained by high pressure torsion under different thermomechanical conditions in terms of temperature and strain magnitude. X-ray diffraction data analysis by Rietveld method has revealed incomplete dissolution of cobalt after 10 anvil revolutions at 300 K. In contrast, the same shear deformation at 80 K leads to complete dissolution of cobalt, accompanied by the formation of two solid solutions with different cobalt contents. The use of magnetic force microscopy has revealed that specimens subjected to mechanosynthesis at 300 K possess the stripe domain structure that is not observed in specimens after cryo-deformation. Vibrational magnetometry of the synthesized alloys has revealed a decrease in the saturation magnetization with increasing shear strain and decreasing temperature of mechanical alloying.

The effect of electrolytic hydrogenation on the mechanical properties and fracture mechanism of the multicomponent Cantor CoCrFeMnNi alloy of different characteristic grain size has been shown. It has been demonstrated that an increase in the density of grain boundaries enhances the resistance of Cantor alloy to hydrogen-induced embrittlement. The primary factors that influence the formation of brittle surface zones during hydrogen charging and subsequent uniaxial tension of hydrogen-charged samples have been identified, and the micromechanisms of their fracture have been elucidated. An increase in grain boundary density impedes the transportation of hydrogen by dislocations during plastic deformation. This is due to the limited free path of dislocations in a fine-grained structure. However, the thickness of the hydrogen-charged layer formed during hydrogen saturation is not significantly affected by the grain size.

Thermo-mechanical controlled processing (TMCP) of low-carbon low-alloy pipe steels is used to attain the required level of mechanical properties in rolled plates designed for pipe production, thereby ensuring the operational stability and reliability of trunk pipelines. The TMCP involves the hot deformation of austenite followed by accelerated cooling, during which the γ → α-transformation occurs. The technological capabilities of contemporary plate mills permit developing and implementing information systems for the control of steel structure and, consequently, its properties. The reliability and accuracy of such systems can be enhanced by using the correct thermophysical parameters of steels. In the present work the critical temperatures, temperature dependences of heat capacities of main phases, and thermal effects of phase transformations in specimens of 05G2MB (wt % ~ 0.05 C; ≤2.0 Mn; ~ 0.2 Mo; ~ 0.05 Nb) high-strength low-alloyed pipe steel have been determined employing differential scanning calorimetry method, dilatometric analysis, and calculations using Thermo-Calc software. It has been demonstrated that the thermal effect of magnetic transformation exhibits a markedly greater value than that of polymorphic phase transformation.