Samples of a diluted dispersion-strengthening alloy of the Cu-Cr-Zr system were processed with a combination of some severe plastic deformation methods. Preliminary, the samples were quenched into water from a pre-melting temperature to create a supersaturated solid solution concentration. In the course of the experiment the average sizes and distribution density of particles with different chemical compositions undergo an evolution that indicates that phase transformations occur even during the cold deformation. A decomposition of the solid solution due to the deformation-induced acceleration of diffusion certainly contributes to this evolution, but the whole complex of the observed results cannot be explained only with this relatively well-studied phenomenon and implies the presence of the deformation-induced dissolution of the second-phase particles. A possible mechanism of the dissolution linking this process to a mechanical fragmentation of the particles in the course of severe plastic deformation is discussed. A dependence of the dissolution efficiency on the composition and related morphology of the particles was also noted. A conclusion on the simultaneously occurring of the kinetically opposite phase transitions is also confirmed by an observation of changes in the lattice constant of copper matrix that are non-monotonous versus the accumulated strain. The crystalline structure refinement upon the severe plastic deformation proceeds through selforganization of dense dislocation pileups into grain boundaries what implies a reverse influence of the second-phase particles, which are effective obstacles to dislocation motion, on the structural transformations. Thus, there exists an interdependence between strain mechanisms and phase transitions such as the second phase particles precipitation and their dissolution in the copper matrix that influences the structure refinement, the dispersion particles distribution in the bulk and, consequently, the strength and other properties of the material. This influence may be especially complicated in alloys that like the one under study have a second phase consisted of particles of many different compositions.

This paper reports experimental results demonstrating nonmonotonic changes of the solid solution concentration in the process of high-pressure torsion of the preliminary aged Cu-Cr-Zr alloy. The solid solution concentration which is very low in the initial state passes through a maximum before it finally stabilizes at a lower value. Such a behavior is, strictly speaking, impossible for a purely diffusion-controlled process under stationary conditions. Observations on the evolution of the second phases particles in the course of deformation suggest a possible mechanism behind this phenomenon. Severe deformation causes refinement of the particles initially present in the alloy by, most probably, quasi-brittle fracture, what creates fragments with sharp edges and makes possible their partial dissolution by Gibbs-Thomson mechanism. The morphology and sizes of the partially dissolved fragments as well as of newly precipitated particles make them less susceptible to fracture than those formed by the preliminary aging. So, under severe deformation, unlike the usually considered models, a "dissolving" subset of particles evolves not only due to diffusion; in the other words, the deformation creates a difference between "dissolving" and "precipitating" subsets of particles. As combined fracture and dissolution transform the initial ensemble of particles, the dissolution gradually slows down unlike the precipitation, which rate is controlled by the solution concentration and density of precipitation sites. As a result, these processes first reach a transitional balance, corresponding to the maximum concentration, and later a stable dynamic equilibrium on its lower level.

An increase in the service life of electrical products from copper and its alloys is directly related to an increase in the wear resistance of materials. Structural refinement and alloying with cadmium are known to have a positive effect on the strength characteristics and wear resistance of copper, which makes it possible, with a Cd content of 1% by weight, to increase the wear resistance of copper several times, but cadmium is considered an environmentally unsafe element. In this regard, the paper presents the results of studies of a widely used Cu-Cr-Zr alloy system in the ultrafine-grained (UFG) state, micro-alloyed with cadmium (0.2%, weight), in order to improve physical, mechanical, and operational properties, as well as environmental safety. Severe plastic deformation, providing structure refinement to ~150 nm, and microalloying with cadmium of a Cu-Cr-Zr system alloy, after a complete processing cycle, provides a tensile strength of 570±10 MPa and 67% electrical conductivity. At the same time, the abrasion resistance increases by 12 and 35% relative to the industrial systems Cu-Cd and Cu-Cr-Zr, respectively. The obtained characteristics are very promising for improving the operational properties of continuous welding tips, collector plates, and contact wires operating under conditions of intense wear.