The temperature dependence of the deformation strength of solid Cu-Al solutions

The temperature dependence of the deformation strength, of the parameters ₀ and K of Pötsch's equation, and of the discontinuous deformation in solid Cu-Al solutions of various concentrations have been studied. It was shown that the temperature dependence of and ₀ changes substantially when the alloy concentration is increased (under otherwise equal conditions). The nature of the processes which lead to the disappearance of the deformation discontinuity and to a sharp high-temperature recrystallization by process annealing is discussed.     

The appearance of the yield point in solid Cu-Al solutions under deformation

The kinetics of yield-point development in solid Cu-Al solutions under deformation at various deformation temperatures has been studied. The nature of the diffusion-strengthening processes which lead to the appearance of the yield point in these alloys, and the particular features of the effect in polycrystals are expounded.     

Contribution from dislocation to deformation resistance in polycrystals of copper-based solid solutions

The evolution of dislocation structure in solid solutions of Cu-Al and Cu-Mn systems with different grain sizes and at different test temperatures is studied by means of transmission electron diffraction microscopy. The scalar density of dislocations is measured and its relationship to the flow stress of alloys is determined. Changes in the contribution from dislocation hardening to deformation resistance upon variations in the contributions associated with changes in grain size, solid-solution hardening, and test temperature are analyzed.     

Contribution of the short-range order to the effects of heat treatment on Cu-Al solid solutions

The contributions from the short-range order to the heat of transition and to the density change are discussed for Cu-Al solid solutions; it is confirmed that the transitions in undeformed Cu-Al solid solutions cannot be explained in terms of the short-range order alone.     

Motive forces of plastic deformation and rotations in crystals with internal boundaries

The forces acting on the internal boundaries from the homogeneous and inhomogeneous components of the stress field are calculated. An interpretation of the torque stress is given, within the framework of theories using symmetric stress in media with an inhomogeneous structure. The reasons for the appearance of plastic deformations and rotations in the crystal are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 65–68, August, 1982.     

Mesoscale plastic flow instability in a solid under high-rate deformation

Here we consider high-rate deformation in solids in the context of a nonlocal transport theory, present a dynamic stress-strain diagram with elastic and plastic portions defined from a single standpoint, determine the conditions for pulse stress accumulation, and propose a mathematical model of momentum and energy exchange between scales and an instability criterion for transient plastic flow under shock loading. Phe instability criterion for high-rate deformation is verified by the example of shock loading of high-strength 30CrNi4Mo steel.     

Dynamics of plastic deformation: Waves of localized plastic deformation in solids

Conclusions It has been shown here that a localized plastic deformation in structurally inhomogeneous media can be of a wave nature and can propagate in the form of nonlinear plastic waves, not only at the microscopic level but also at the mesoscopic level. It has been established that there is an interrelationship between this new effect and grain-boundary slippage (an effect which has been under study for a long time) and also with certain types of quasiviscous fracture in plastically deformable materials.We have discussed certain specific practical problems in the mechanics of plastic deformation, and for certain types of fracture. In the future, these problems will be discussed at a more profound level and in greater detail, because of experimental studies which are presently being carried out on the dynamics of deformation for various types of loading and fracture [17, 18, 31]. We hope that the approach proposed here for a theoretical study of the localization of deformation and fracture can be taken to study such effects as splitting off [31], the influence of defect fluxes on grain-boundary slippage [22], superplasticity [23], the behavior of tectonic faults and boundaries of various types [32], electroplastic and magnetoplastic effects, and high-temperature localization of deformation [25].The general nature of the approach proposed here results from the circumstance that a localization of deformation is present explicitly or implicitly during plastic deformation, and the behavior of this deformation plays a role of fundamental importance in the propagation of plastic deformation through a material.The author wishes to thank V. E. Panin for a constant discussion of this problem and I. O. Nedavnii for carrying out the numerical calculations.V. V. Kuibyshev Tomsk State University. Institute of Strength Physics and Materials Science. Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 19–41, April, 1992.     

Study on the mechanism of hardening polycrystals of solid solutions Cu-Ni,Cu-Zn,Cu-Al,and Cu-Ge at microdeformation stage

The stress-strain curves were obtained at the stage of microdeformation of polycrystals of the solid solutions Cu-Ni, Cu-Zn, Cu-Al, and Cu-Ge. It was demonstrated that the shape of the stress-strain curves below the yield point depends on the concentration, the distribution of atoms of alloying elements, the properties of the components of the alloy, and on the size of grain. The dependence of the modulus of strain hardening on the composition of the alloys and on the grain size was analyzed. It was concluded that the magnitude of the modulus of strain hardening at the initial stage of microdeformation is determined by the character of the involvement of the individual grains in plastic deformation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 86–92, December, 1972.     

Formation and properties of copper-silver solid solutions upon severe deformation under pressure

Nonequilibrium nanocrystalline FCC solid solutions are obtained via the mechanical alloying of Cu_{1.0 ? x} -Ag _x powders (x = 0.1, 0.2, …, 0.9, 1.0) with deformation under pressure and their properties are investigated. The chemical homogeneity, microstructure, mechanical properties, and thermal stability of the alloys are investigated. The alloys have the positive deviation of lattice parameters from the Vegard law with crystallite sizes of 20 nm, hardness exceeding the initial values of the components by 4.5–6 times, and a brittle character of fracture. The thermally induced decomposition of nonequilibrium solutions starts at temperatures close to room and is complete after heating to 500°C with the development of collective recrystallization.     

Electrical resistance and thermophysical properties of solid solutions of germanium in iron

Temperature dependence of thermal diffusivity, thermal conductivity, and electrical resistance is studied in solid solutions of germanium in iron at impurity concentrations of 0.49–18.0 at.% Ge over the temperature range 300–1300K. The results obtained are evaluated and compared to similar dependences for the system Fe-Si.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 36–41, June, 1984.     

Avalanches and scaling in plastic deformation

Plastic deformation of crystalline materials is a complex nonhomogeneous process characterized by avalanches in the motion of dislocations. We study the evolution of dislocation loops using an analytically solvable phase-field model of dislocations for ductile single crystals during monotonic loading. The distribution of dislocation loop sizes is given by P(A) approximately A-sigma, with sigma=1.8+/-0.1. The exponent is in agreement with those found in acoustic emission experiments. This model also predicts a range of macroscopic behaviors in agreement with observation, including hardening with monotonic loading, and a maximum in the acoustic emission signal at the onset of yielding.     

Role of packing-defect energy in the localization of plastic strain during shock-wave loading of copper-based solid solutions

The formation of deformation structure accompanying a change in the packing-defect energy (PDE) and the conditions of deformation of copper-based solid solutions under shock-wave loading were investigated by the method of optical microscopy. It is shown that in the case of solid solutions with high PDE plastic strain is localized. This localization increases with the amplitude and duration of the shock pulse, and this in turn gives rise to the generation and growth of microcracks. V. D. Kuznetsov Siberian Physicotechnical Institute at Tomsk State University. Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 2, pp. 30–34, February, 1993.     

Electronic excitations owing to plastic deformation of ionic crystals

Electron emission and luminescence accompanying plastic deformation of alkali halide crystals are studied. It is shown that the intersection of dislocations can cause electronic excitation. Deformation electron emission and luminescence are produced by relaxation of these excitations. Fiz. Tverd. Tela (St. Petersburg) 41, 900–902 (May 1999)