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Structural and phase transformations in a commercial multicomponent aluminum–lithium alloy have been studied electron-microscopically upon storage after mega-plastic deformation by high-pressure torsion. It has been shown that the arising deformation structure of the alloy is unstable, and upon subsequent storage at room temperature it is transformed via a complex reaction of in situ recrystallization and decomposition of the supersaturated solid solution. The character of the transformation is determined by the regime of the previous mega-plastic deformation and by the duration of the storage.

Metallographic analysis, hardness and electrical resistivity measurements, and tensile tests are used to study the behavior of Al–Mg2Si alloys with (Sc + Zr) transition metal additions during aging performed after preliminary deformation under different conditions. It is shown that the decomposition of the supersaturated solid solution in the Al–Mg2Si alloys with (Sc + Zr) transition metals and without them occurs in the same manner. However, the strength properties of the alloys with transition metals are higher than those of the alloys free from the transition metals because of substantial refining of solid-solution grains and a high density of dispersoid (Sc1 –xZrx)Al3 aluminide particles. A peak hardness is observed for the alloys after quenching, equal channel angular pressing (ECAP), and aging. However, cold rolling after quenching before aging leads to an increase in the strength properties to a greater extent than ECAP performed under the same conditions.

The decomposition of supersaturated solid solution in the Cu–0.06 wt% Zr alloy has been investigated. Upon aging of the initially quenched alloy the homogeneous precipitation of particles is dominating. The decomposition begins from the precipitation of a metastable copper–zirconium phase, the particles of which have the shape of nanodimensional disks. An increase in the aging temperature results in the formation of coarser rodlike particles of the Cu5Zr equilibrium phase. Aging of the deformed alloy is characterized by the predominance of the heterogeneous precipitation of particles at subboundaries and dislocations, and the decomposition begins at a lower temperature. The particle size is less by an order of magnitude than that in the quenched state. The precipitation of nanodimensional particles at dislocations retards the formation of recrystallization centers.

Hypotheses on how first-order phase transitions develop which deny a fundamental element of the classical thermal fluctuation theory, namely, that the nucleation of a new phase must take place when the crystal lattice changes, are considered. It is shown that the thermal fluctuation theory does not work for polymorphic transformations in pure metals, which are accompanied by lattice rearrangement in a macrovolume (over the entire volume of a sample under study) without substance transfer. However, the classical thermal fluctuation theory of new phase nucleation is valid in describing the supersaturated solid solution decomposition in the case where the main pattern of the crystal lattice of the matrix is retained, and a new phase, which differs from the parent one in both crystal structure and chemical composition, precipitates in separate microvolumes.

The effect of severe plastic deformation on the decomposition of supersaturated solid solution has been investigated. A study has been performed on a metastable niobium-titanium alloy (NT-50). It has been established that an increase in the true plastic prestrain of the NT-50 alloy from 4 to 7.6 leads to the significant acceleration of supersaturated solid solution decomposition at all treatment times (from 50 to 2000 h). The volume fraction of the precipitated α-Ti phase increases by ∼(40–50)%. The true prestrain growth brings changes in the mechanisms responsible for the increase in the fracture of the precipitated phase. At the increased true prestrains, the volume fraction of the phase increases with growing sizes of precipitates at a constant and even slight decrease in their density, while at smaller true prestrains, the growth occurs at the expense of the increased number density of the precipitated particles with approximately the same sizes.

The changes in the structure and properties of the high-strength magnesium alloy IMV7-1 of a Mg-Y-Gd-Zr system are studied after heating at various temperatures. The alloy is hot-worked before annealing to obtain wrought semifinished products. The high stability of a hot-worked structure in annealing is established. It indicates the possibility of using the alloy as a light structural material at elevated (up to 300°C) temperatures. As the annealing temperature increases to 400°C and the holding time is one or two hours, there is only a slight decrease in the hardness, characterizing the strength properties of the alloy. With a further increase in the annealing temperature, a sharp fall in the hardness is observed. Investigation of the structure shows recrystallization in the alloy after annealing at temperatures up to 400°C. After annealing at higher temperatures of 450 and 500°C, the abrupt fall in the hardness is accompanied by complete disappearance of the elongated deformed grains which exist in the hot-worked state and by a significant grain growth. After recrystallization, the alloy retains the ability to be significantly strengthened upon aging, resulting in decomposition of the magnesium-based supersaturated solid solution.

The N30K10T3 and N40K10T3 invars with the Curie points θC ≈ 200°C and θC ≈ 310°C and the martensite temperatures Ms ≈ −80°C and Ms < −196°C, respectively, have been studied. The two alloys were hardened by quenching in the range of temperatures from 100 to 750°C. In addition, the first alloy was hardened by a combination treatment including phase-transformation-induced hardening and aging. The method of phase hardening consisted in the use of a forward (γ → α) and a reverse (α → γph) martensitic transformations. It has been shown that the temperature dependences of the linear expansion coefficient and the dependences of the hardness on the temperature and time of aging are considerably different for both alloys upon decomposition of the supersaturated solid solution. Both the ordinary and the double aging have been studied.

The N30K10T3 invar that has a temperature of the onset of martensite transformation of austenite Ms ≈ −80°C and a Curie point θC ≈ 200°C after water-quenching from 1150°C is studied. The decomposition of a supersaturated solid solution is shown to substantially influence the linear thermal expansion coefficient. The alloy is studied in the following three initial states: after quenching, after phase transformation-induced hardening (γ → αm → γp.h), and after cold (20°C) plastic deformation by 30%.

Effect of a pulsed magnetic field and low-temperature tempering on the carbon amount in the martensite of a quenched 65G steel has been considered. The treatment by pulsed magnetic field and subsequent exposure for 12–24 h of quenched samples of the 65G steel result in the same effects of a decomposition of the supersaturated solid solution (martensite) as those observed upon heating in the temperature range from 100 to 200°C.

Concentration and structural inhomogeneities in highly doped GaSb(Si) single crystals grown under various conditions of heat and mass transfer are studied by methods of X-ray topography, high-resolution X-ray diffractometry, and digital image processing. It is established that the inhomogeneity of crystals is determined by specific features of impurity microsegregation during growth under conditions of nonstationary convection in a melt and by peculiarities of the dislocation structure of crystals. The processes related to the initial stage of the decay of the Si supersaturated solid solution in GaSb contribute considerably to the inhomogeneity of crystals on the micro- and macrolevels.

Kinetics of decomposition of the supersaturated solid solution in the Mg-3.3 wt % Yb alloy has been investigated during aging in a temperature range of 150–225°C using electron microscopy, X-ray diffraction, and hardness measurements. Mechanisms of the decomposition of the supersaturated solid solution and the nature of phases precipitating at different stages of aging, namely, in the underaged, maximum-hardness, and overaged states, have been established. The character of structural components responsible for the hardness changes during aging process has been established.

The magnesium solid solution in the Mg-Al-Ca system is confirmed to be in equilibrium with the Al2Ca phase of the Al-Ca system. The solubility of Al2Ca in solid magnesium is determined, and its decrease with decreasing temperature suggests the decomposition of a supersaturated solid solution in Mg-Al2Ca alloys. The decomposition kinetics of the supersaturated solid solution and the accompanying strengthening effect in the alloys at aging temperatures of 175 and 200°C are established.

The decomposition of a solid solution of iron in gallium arsenide at 900°C has been studied by magnetic force microscopy and transmission electron microscopy. The results demonstrate that annealing of Fe-doped GaAs for 3 h leads to the formation of disk-shaped ferromagnetic inclusions 50–500 nm in diameter and 1.5–50 nm in thickness. The average inclusion concentration is 1011 cm−3. The estimated decomposition time of the solid solution at 900°C is within 1 h.

Data obtained to date on specific features of defect formation for hydrogenated single-crystal Si are analyzed. It was demonstrated that, in addition to other effects, interaction of H atoms with radiation defects and impurities leads to the formation of large clusters of three main types, namely, vacancy, interstitial, and impurity clusters. The main condition for formation of these clusters is the simultaneous presence of supersaturated solutions of H and defects in the sample. The interaction of H atoms with impurities and defects initiates the decomposition of the supersaturated solid solution of defects and impurities with the formation of precipitates. This leads to the formation of clusters, which are not observed in the absence of H. The mechanisms of formation and structure of clusters are discussed.

The mechanism of grain refinement in the process of nucleation and growth of cells of discontinuous precipitation in the Pb-5 wt % Sn alloy has been investigated. In the case of the nucleation of cells according to an S-like mechanism, there occurs a “splitting” of the initial grain boundary into three boundaries of two adjacent cells. The boundary between the cells is fixed, the boundaries of the growing cells move into the supersaturated solid solution until the collision with other cells. The possibility of the passage of intercrystallite microcracks into the bulk of grains in the process of the discontinuous precipitation is shown.

The late stages of diffusive decomposition of a supersaturated solid solution into phases consisting of multicomponent stoichiometric compounds with a common element are investigated. It is shown that a competition is possible between phases for the common component, as a result of which only one of these phases survives.