Yu.M. Ustyugov

The magnetic, electrical, and optical properties of the high-entropy equiatomic AlCrFeCoNiCu alloy produced by rapid quenching from the melt by spinning at a cooling rate of 105–106K/s have been...

We report on the results of analysis of the phase composition, structure, and hardness of high-entropy FeWMoCrVSiMnC multicomponent steel subjected to synthesis and subsequent thermal treatment....

The results of studying the phase composition, structure, and hardness of a synthesized multi‐component Fe–W–Mo–Cr–V–Si–Mn–C steel are presented. Investigations were performed via using methods of the analytical transmission and scanning structural and orientation electron microscopy, optical metallography, X‐ray energy‐dispersion spectroscopy, X‐ray phase and structure analysis, measurements of Rockwell hardness. It has been established that the steel has a high hardness (62 HRC) and is in an ultrafine‐grained composite‐wise martensite–multi‐carbide state. In this case, all different type of carbides are uniformly distributed over the volume of the steel and are of either nano‐ or submicro‐crystalline size in dependence of the type of the carbide phase. The state of the steel, synthesized via laser remelting, from the viewpoint of the character of the spatial distribution of the chemical and phase constituents, has turned out to be very much resembling that one which is typical of some high‐entropy alloys already studied.

In this paper, we have studied the relaxation processes that occur upon the decomposition of solid solutions at the stage of coalescence in the regime of dislocation-matrix diffusion using the precipitated-phase-particle-feeding-dislocations system as an example. The cases of linear and nonlinear interrelations between the controlling parameters of the system (the fraction of the relaxed regions of the interphase surface and the number of edge dislocations that supply the alloying component to the precipitated phase) have been analyzed. It has been established that in real cases it is advantageous for the system to reduce its total energy via the “infiltration” of feeding dislocations, i.e., the escape of segments of edge feeding dislocations localized in the precipitate outside the limits of the precipitate with the formation of structural dislocation loops at the interphase surface by the reaction of the following type: 1 feeding dislocation = 1 structural loop + 1 matrix dislocation. In the presence of an enhanced density of feeding dislocations, this reaction is blocked, and the relaxation of interphase stresses is accomplished as a result of sequential acts of the loss of coherence, which are accompanied by a partial “escape” of edge feeding dislocations. For the edge dislocations that remain unescaped, there is formulated a condition for the subsequent “leakage” of their segments localized in the precipitate outside the limits of the precipitate according to the following reaction: 2 feeding dislocations = 1 structural loop + 2 matrix dislocations.

The study of relaxation processes upon the decomposition of solid solutions at the stage of coalescence in the regime of dislocation-matrix diffusion is performed using a “precipitated-phase-particle-feeding-dislocations” system as an example. Within the framework of the variational approach, the cases of the independent and interdependent variation of the fraction of the relaxed regions of the interphase surface and of the number of edge dislocations which supply the alloying component to the precipitated phase have been investigated. Under the assumption that implies the linearity of the possible connection between these parameters, the model approximation of the continuous nucleation of epitaxial defects, and the absence of free matrix dislocations near the particle in the initial state, it is shown that the decrease in the number of edge feeding dislocations in the process of relaxation of interphase stresses can occur only by means of “leakage” of dislocation segments localized in the precipitate outside the limits of the precipitate with the formation of structural dislocation loops on the interphase surface.

For describing the isomorphic heterogeneous decomposition of binary supersaturated solid solutions at the stage of coalescence under conditions of dislocation-matrix diffusion with a relaxation of stresses caused by phase separation, we consider a system representing a precipitation-phase particle in a surrounding matrix + dislocations intersecting the interphase surface and supplying an alloying component to it. In the approximations based on the continuity of the distribution of misfit dislocations on the interphase surface and of the average concentration field, we obtained an expression for the total energy of the system in the form of a functional which depends on the fraction of the relaxed regions of the interphase surface, the number of supplying (feeding) dislocations, and their mutual arrangement. The need for the use of a model functional appears within the framework of the variational problem for determining the equilibrium parameters of the system.

On the basis of a theoretical analysis of asymptotic states which are formed under the conditions of an enhanced density of matrix dislocations in different stages of decomposition of supersaturated solid solutions in concrete diffusion regimes, it is shown how the universal function of relative particle-size distribution is connected with the functional parameter m which is the only carrier of information on the amount of preliminary deformation ε of an aging alloy. This parameter as a function of ε is approximated by a step. The smearing and height of this step are determined from the found conditions of the realization of dislocation diffusion as the mechanism which controls coalescence in the initial and final (in the case of smallness of ε, very remote in time) stages of the evolution of a heterophase structure. Thereby, an explicit dependence of the universal distribution function on the deformation and the temperature and duration of aging is established.

The object of a theoretical examination is here the heterogeneous isomorphic continuous decomposition of supersaturated solid solutions for the case of binary aging alloys with a developed dislocation structure under enhanced temperatures in the unsteady stage of coalescence, whose transient nature is caused by the instability with respect to a change in the mechanism of mass transfer acting in the system, which controls coarsening of the disperse heterophase structure. For the quasi-stationary diffusion regime, a complete analytical description of the evolution of the second-phase-size distribution function is given for the stage of the transient kinetics, when the initially prevailing diffusion along dislocations, which supply the alloying component to the precipitation phase, is succeeded by volume diffusion at the last stages of decomposition.