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The α+β titanium alloy Ti-6Al-4V having different structure and phase composition is investigated in this paper under the tensile deformation in the temperature range from 773 to 1223 K. The transmission and scanning electron microscopy observations show that superplastic deformation of the Ti-6Al-4V alloy with the ultra-fine grain structure produces the formation of the secondary phase particles along the grain boundaries. It is identified that this process is connected with the vanadium redistribution during deformation. The obtained temperature dependence of the fracture elongation of the alloy samples is nonmonotonic and exceeds 700% at 973 K. It is supposed that the reduction in the fracture elongation within 1073–1173 K range is associated with the deformation-induced micron-sized grains and the formation of lamellar β- and α″-phases along the grain boundaries.

The effect of annealing at 673 K for 6–24 h on the structural and phase state and mechanical properties of the titanium alloy of a Ti-Al-V system that was previously subjected to severe plastic deformation by uniform compression deformation, has been studied. It has been established that these annealings lead to a nonmontonic dependence of the mechanical properties of the alloy on the annealing time. It has been shown that the annealing of the Ti-Al-V alloy in a submicrocrystalline state is accompanied by simultaneous hardening processes, i.e., the formation of fine particles during phase transformations and the formation of new nanosized grains, and softening processes, i.e., recovery processes and the growth grains to micron sizes. The prevalence of a given process during annealing determines the deterioration or improvement of the alloy’s mechanical properties.

Grain-boundary misorientations and mechanical properties of ultrafine-grained (UFG) nickel produced by equal-channel angular pressing are investigated after rolling at a temperature of −196°C. It is shown that cryogenic rolling increases the fraction of high-angle grain boundaries almost two times in UFG nickel. The approach based on electron backscatter diffraction analysis is proposed to estimate the relative energy of high-angle boundaries in polycrystalline metals.

The special features of the ultrafine-grained structure forming in a Ti-6Al-4V alloy with the use of a method combining severe plastic deformation and reversible hydrogen treatment are studied by electron microscopy and X-ray diffraction analysis. Martensite and the α ↔ β phase transformations due to hydrogen presence are found to promote structure refining during severe plastic deformation of the alloy. This makes it possible to decrease the degree of deformation required for obtaining the ultrafine-grained structure with the size of elements of 0.1–0.5 μm. Formation of the ultrafine-grained structure in a Ti-6Al-4V alloy is shown to lead to growth of its strength properties by approximately a factor of 1.5, an increase in the hydrogen embrittlement resistance, and a decrease in the temperature transition to the superplastic state by 200–300 K.

Using the method of equal-channel angular pressing (ECAP), submicrocrystalline structure is formed in lowcarbon Fe–Mn–V–Ti–C steel with the average grain size 260 nm in the ferrite-perlite state and 310 nm in the martensitic state. It is established that the ECAP treatment gives rise to improved mechanical properties (Hμ = 2.9 GPa, σ0 = 990 MPa in the ferrite-perlite and Hμ = 3.7 GPa, σ0 = 1125 MPa in martensitic states), decreased plasticity, and results in plastic flow localization under tensile loading. The high strength properties formed by the ECAP are shown to sustain up to the annealing temperature 500°C.

An analysis of the diffraction patterns from backscattered electrons and of measured microhardness has been performed to investigate the distributions of structural parameters (average grain/subgrain size and fraction of high-angle grain boundaries) and of the mechanical properties in the longitudinal section of a pure aluminum billet subjected to severe plastic deformation by equal-channel angular pressing. The distributions of the characteristics under study were found to be nonuniform. A minimum average grain size and a maximum fraction of high-angle boundaries were observed in the core of the billet. As the sample surface was approached, the examined parameters were seen to vary in magnitude through a broad range. Conceivable reasons for the structural heterogeneity of the material are discussed.

Transmission electron microscopy, X-ray diffraction, and electron back-scattering pattern analysis have been used to investigate the effect of the speed of equal-channel angular pressing (ECAP) at room temperature on the formation of ultrafine-grained structure in pure aluminum. It has been established that eight ECAP passages with a pressing speed of 3.3 × 10−2 mm/s results in the formation in aluminum of a substantially inhomogeneous grain structure with a grain size in the range of 1–27 μm (average size 3.0 μm). An increase in the speed of pressing by an order of magnitude leads to an increase in the level of internal stresses and dislocation density, an increase in the upper boundary of the interval of the grain-size distribution and in the average grain size (to 3.4 μm), and a decrease in the number of boundaries with high-angle misorientations. It is assumed that these changes are connected with the fact that processes of dislocation-structure relaxation have no time to occur during the ECAP at high pressing speeds.

The special features of the evolution of the structural and phase states of a Ti-6Al-4V alloy in forming submicrocrystalline structure with the use of temporary hydrogen treatment are studied by electron microscopy and x-ray diffraction analysis. Plastic deformation in the α + β two-phase region at 1023 K is found to initiate a complete β → α transformation in a Ti-6Al-4V-H alloy to form an α phase with lattice parameters different from those of the equilibrium α phase. Isothermal annealing at a dehydrogenation temperature of 873 K gives rise to α + β two-phase submicrocrystalline structure with a grain size of ∼ 0.3 µm. The use of nonequilibrium hydrogen release in the deformed Ti-6Al-4V-H alloy exposed to electron beams is shown to result in one-phase submicrocrystalline structure and grain refining. Possible reasons underlying the phase transformations in the alloy under study are discussed.

The structural-phase state and mechanical properties of commercial aluminum alloys produced by severe plastic deformation are studied and compared to the initial polycrystalline state. This kind of treatment is found to give rise to the formation of a homogeneous ultrafine-grained structure with second-phase particles occurring predominantly along grain boundaries. With this structure, the strain-temperature and strain-rate intervals wherein the superplastic properties of the alloys under study are observed are shifted to lower temperatures and higher rates.

Comparative investigations of the effect of diffusion streams of copper atoms (a weakly segregating impurity) and silver atoms (a strongly segregating impurity) from the surface in the high-temperature plastic deformation of nickel have been carried out. It has been established that in the high-temperature plastic deformation of nickel, when there are diffusion streams of copper and silver from the surface, there is a reduction in the creep resistance of nickel due to an increase in the contribution of grain-boundary slip to the overall deformation. Two stages, characterized by different values of the rate sensitivity factor m, are observed on the curve of the stress against the rate of deformation over a certain temperature range for each impurity. In the region of deformation rates of $$\dot \varepsilon< 2.5 \cdot 10^{ - 6} $$ sec−1, m≊0.2, and for $$\dot \varepsilon > 2.5 \cdot 10^{ - 6} $$ sec−1, m becomes less than 0.05.

We have investigated the effects of surface copper diffusion on the creep of large-grain nickel (average grain size about 20 m) and submicron crystalline nickel (grain size about 0.3 m). For both structural states of nickel we find an acceleration of creep over its value in vacuum, and an increase in plasticity during creep when copper has diffused deeply into the nickel from the surface. The temperature range over which these effects are observed in the submicron nickel is nearly 300° lower than that for the large-grain samples. This result is probably due to a significant increase in the grain-boundary and bulk diffusion coefficients of copper in submicron nickel when compared with large-grain nickel.