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.

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The polarization of the secondary protons in the (p, 2p) reaction with the S-shell protons of nuclei 4 He, 6 Li, 12 C, 28 Si, 40 Ca was measured at 1 GeV unpolarized proton beam. The spin correlation parameters C ij for the 4 He and 12 C targets also were for the first time obtained as well. The polarization measurements were performed by means of a two-arm magnetic spectrometer, each arm of which was equipped with the multiwire-proportional chamber polarimeter. This experiment was aimed to study a modification of the proton-proton scattering matrix in the nuclear medium. Comments: 28 pages, 7 figures, 6 tables, Submitted to the journal "Physics of Atomic Nuclei" Category: Nuclear experiment (nucl-ex)

Changes of properties and the second phase particles' distribution in diluted CuCrZr alloy in the course of equal channel angular pressing (ECAP) and post-deformation annealing are investigated. To decrease the concentration of alloying elements dissolved in the copper matrix, samples of the alloy were thermally aged prior to the ECAP. Temperature of annealing, 450°C, was the same as the one used for the subsequent post-deformation aging, and the time of annealing was long enough to reach a practically equilibrium state. The enthalpy release rate curve of the ECAP-processed sample, unlike the one for the initial state exhibits an exopeak in the temperature range 440..470°C, which is typical for breakdown of the solid solution in alloys of this system. The post-deformation aging causes a significant increase in the tensile strength as compared to the value immediately after the ECAP. This increase can be related only to the dispersion strengthening that is confirmed by the observation of higher density of particles after the aging. These facts unambiguously indicate that the solid solution at the aging temperature is supersaturated, i.e. its concentration increased in the course of the ECAP due to the deformation-induced dissolution of the second phases. This conclusion agrees with the behavior of the electrical conductivity that noticeably decreases upon the ECAP and recovers its initial value after the aging. As the density of structural defects is significantly different in the initial and final states, the observed decrease can be related only to the lattice distortion due to dissolved foreign atoms.

We studied the effect of the regimes of ultrasonic action on the structural transformation during free upsetting with 50% reduction of the copper alloy Cu–0.5Cr. In the process of deformation, the samples were subjected to intermittent and continuous ultrasonic actions. It can be noted that the application of ultrasonic vibrations in the process of deformation leads in both cases to a reduction in yield strength. Under a continuous ultrasonic action with a power of 640 W, the most developed structure is formed, with a fraction of high-angle boundaries equal to 32.4%, with the lowest values of coherent scattering regions, density of dislocations and microdistortions, while the decline in yield strength of the material under deformation is 40 MPa. This paper is part of a Thematic Issue on Copper and its Alloys.

Various contributions to the overall strength of the Cu-1Cu-0.7Al-0.2Zr alloy after the combined severe plastic deformation treatment have been calculated and compared with those after the standard industrial processing. Contrary to the common viewpoint, the SPD increases the strength not only due to the structure refinement, but also because of greater contribution of the dispersion strengthening. It is argued that this effect is linked to the deformation-induced phase transitions upon the SPD.

Работа посвящена изучению влияния структуры и размеров зерна на изменение микрорельефа и оптических характеристик образцов зеркал из медных сплавов с существенно различными размерами зёрен при бомбардировке их ионами дейтериевой плазмы. Исследование проведено в рамках решения задачи выбора материала обращённых к плазме зеркал для оптических методов диагностики плазмы в термоядерном реакторе. На основании комплексных исследований структурных особенностей поверхностного слоя образцов зеркал из низколегированных медно-хромовых сплавов сделан вывод об определяющей роли размера зерна на их поведение при воздействии дейтериевой плазмы. Ключевые слова: хромо-циркониевые медные сплавы, первое зеркало, оптические свойства, ионное распыление.