There are studied the structure formation of the high-strength casting Cu-Al alloys. Providing high level of properties for such alloys is connected by maintaining the necessary Cu content and alloying special strengthening additives. The most effective additives are unfortunately toxic Cd or expensive Ag. It is proposed to remove such components from the composition of alloys. To provide the structure dispersion and an increasing of properties, other alloying and modifying components, in particular, Mn and Zr, should be used. There are developed the technological bases for obtaining master alloys Al-Mn and Al-Zr with applying the energy of electromagnetic fields and magnetodynamic equipment. Modes for adding made master alloys into experimental liquid high-strength casting Cu-Al alloy are worked. As result, it is provided the substantiate refining of the cast alloy structure. To provide further structural transformations and to increase the properties of the experimental alloy, as well as due to a change in its chemical composition, the modes of its heat treatment are clarified. The proposed mode is similar to T6 and includes two- stages' homogenization (annealing) under quenching in water and subsequent artificial ageing. The further development of research consists in determining the new alloying components for such alloys. These components should make a strengthening effect on the structure, promote properties' increasing, and, at the same time, are non-toxic and relatively cheap.

The melt treatment in the magnetodynamic apparatus using the ARSAL refining flux and modification of phosphorous copper were applied to hypereutectic Al-Si alloys to investigate their structural changes and properties. It was shown that such treatment of the melt in the magnetodynamic installation using the ARSAL refining flux and properly chosen heat treatment of the solidificated alloys allows us to refine primary silicon particles, reduce segregation of alloying elements, increase the supersaturation of solid solution, to enlarge the volume fraction of the nanoparticles formed during the aging process. As a result, the strength characteristics are increased: tensile strength σB increases from 322 MPa in the initial state to 353 MPa, yield strength σT-from 280 MPa to 317 MPa and elongation δ increases from 0.78 to 1.55%.

The paper addresses decomposition processes of supersaturated solid solutions of Al–Mg alloys alloyed with transition metals. Al–(3.5–4)aт.%Mg–(0.25–0.5)aт.%Sc–(0.15–0.75)aт.%Zr–(0.04–0.12)aт.%Hf alloys with Sc/Zr ratios 5:2:1:0.3 have been chosen for study. The alloys were obtained by melt spinning at the quenching temperature of 1000 °C. The annealing in the temperature range of 300–450 °C was carried out to study aging processes in the alloys. Their structure and mechanical properties were examined using transmission electron microscopy (TEM), X-ray diffractometry, and hardness measurements. The temperature ranges of phase transformations were determined by measuring the temperature coefficient of resistivity α t  =  1/ρ 0 dρ/dT . It has been shown that the highest thermal stability of the alloys is achieved when the Sc/Zr ratio is equal to 1.

The changes in the structural state of the base Al-3Zr wt% alloy depending on the casting temperature, quenching cooling rate, and the target alloying were studied. It was shown that low cooling rate of 101 deg/sec of the base alloy causes formation of two preferential size (about 10 and 2 µm) of dispersed particles that uniformly distributed in the Al-0.12Zr wt% matrix. Increasing cooling rate to 103 °/s causes rise of Zr content in the matrix from 0.12 to 2.4 wt%. Thus, in this case, a precondition of formation of nano-sized Al3Zr hardening particles is appeared. At the highest cooling rate (106 °/s), turbulent convection flows are formed, as well as a vortex structure with Al3Zr particles. The addition of 3–4% Mg to the base alloy increases the melt viscosity, suppresses thermal diffusion processes, levels the concentration on the free and contact side, and increases the degree of supersaturation of the solid solution. The use of Sc, Er micro-alloying completely eliminates the formation of large particles, and contributes to the refining of primary intermetallic compounds to d ~ 1 μm with a significant increase in their precipitation density.

An effective alloying system for providing improved mechanical and technological properties of model cast Al–Cu alloys (Al-4.6%Cu-0.4%Mn-0.2%Ti), using magnetohydrodynamic (MHD) melt mixing, has been chosen in this research. It was shown that MHD treatment provides a non-dendritic (globular) ingot structure and can be applied to ensure thixotropy in the mass production of high-precision cast parts. Small additives of alloying elements that modify both grain structure (Mn, Zr) and reinforcing phases (Sn, In, Sc) were used. It is shown that the most effective alloying elements which improved the strength characteristics of the alloy are Sn and In. The introduction of 0.1–0.2% Sn or In followed by heat treatment led to a 50% increase in its yield strength, a 15% increase in the tensile strength. Sn and In modified the decomposition kinetics, providing a high density of precipitate and slow coalescence of nano-sized particles of the strengthening θ′-phase, which resulted in higher strength characteristics of the alloy.

The effect of long-time homogenization and aging on the formation of disperse β ′ phase particles and β phase particles has been analyzed. Alloys solidified with the cooling rate of ∼10 − 1 °C/s (Al–10%Mg and Al–10%Mg–0.1%Sc) and alloys melted by centrifugal casting with the cooling rate of ∼ 10 3 °C/s (Al–10%Mg) were chosen for comparative analysis. А significant heterogeneity of the distribution of the strengthening β ′-phase after aging is observed in Al–10%Mg alloys obtained by the ingot technology. The greatest hardening up to 100% is achieved after using the centrifugal casting due to the formation of the β ′-phase during aging.

The precipitation of intermetallic compounds of transition metals during aging of the Al–5.8%Cu–0.3%Mn–0.1%Zr alloy has been studied using DSC, resistometry, X-ray and transmission electron microscopy. In these age hardenable alloys, the nanoscale metastable Θ″ and Θ′ phases of the Al2Cu compound are the main strengthening phases, which are formed at low temperature aging of T < 300 °C. The effect of high-temperature treatment (homogenization, heating for quenching, heating for the elimination of internal stresses, etc.) on the aging with the precipitation of strengthening phases has been investigated.

The comparative analysis of the effect of monotonous and non-monotonous severe plastic deformations (SPD) on the structure and properties of aluminum alloys has been carried out. Conventional hydrostatic extrusion (HE) with a constant deformation direction and equal-channel angular hydroextrusion (ECAH) with an abrupt change in the deformation direction were chosen for the cases of monotonous and non-monotonous SPD, respectively. Model cast hypoeutectic Al-0.3%Sc alloys and hypereutectic Al-0.6%Sc alloys with Ta and Ti additives were chosen for studying. It was demonstrated that SPD of the alloys resulted in the segregation of the material into active and inactive zones which formed a banded structure. The active zones were shown to be bands of localized plastic deformation. The distance between zones was found to be independent of the accumulated strain degree and was in the range of 0.6–1 μm. Dynamic recrystallization in the active zones was observed using TEM. The dynamic recrystallization was accompanied by the formation of disclinations, deformation bands, low-angle, and high-angle boundaries, i.e., rotational deformation modes developed. The dynamic recrystallization was more intense during the non-monotonous deformation as compared with the monotonous one, which was confirmed by the reduction of texture degree in the materials after ECAH.

УкраинаВ сплавах Al-Sc, Al-Sc-Ti, Al-Sc-Ta при интенсивной пластической деформации методами гидроэкструзии и равноканальной угловой гидроэкструзии при комнатной температуре образуются домены с периодической структурой, в которых чередуются области деформированной и недеформированной матрицы с периодом модуляции 0,4-0,7 мкм.Такая структура обусловлена тем, что

The mechanism and kinetics of Al3Li/Al3Sc composite particles formation during aging of triple Al-Li-Sc alloys were studied. The particles of such type consist of two isomorphic phases, ordered by L1(2) type. Composite particles in Al-Li-Sc are formed by epitaxial nucleation of delta'(Al3Li) phase on pre-existing Al3Sc precipitates at low temperature aging in the area of existence of Al3Li phase, and form uniform shell around them. The motive force of such heterostructure formation is the minimization of total surface, elastic and chemical energy of the alloy. Dark-field transmission electron microscopy images of such composite particles taken from superlattice reflex 100 are composed of a dark core surrounded by a bright shell. The mutual diffusion of Li and Sc during the aging of Al-Li-Sc alloys is observed. The dark-field transmission electron microscopy image of the composite particle obtained from superlattice reflection became transparent after continuous natural aging of Al- Li-Sc alloys. The presence of the particle in Al matrix can be only seen due to decoration by secondary precipitations of delta'(Al3Li) phase. Composition analysis of such transparent particles was carried out using two-beam kinematical theory of electron diffraction. Such composite particles with transparent cores remain in Al matrix even after severe plastic deformation of Al-Li-Sc alloy.

Evolution of the microstructure and mechanical properties of the hypereutectic Al-16.5mass%Si-3.77mass%Cu alloy by treatment in the liquid state by magnetohydrodynamic (MHD) and hydrodynamic (HD) methods, followed by processing in the solid state by equal channel angular pressing (ECAP) method and thermal treatment has been investigated. This alloy has in initial state a very low value of plasticity at room temperature. Optical microscopy technique was employed in order to determine the evolution of the microstructure after different operating conditions of ECAP and thermal treatments. It was demonstrated that it is possible to significantly improve mechanical properties of this alloy by means of combining a low number of ECAP passes after an adequate combination of MHD+HD processing and thermal treatments.

The study of the effect of ultrasonic shock treatment on the structure of Al-Mg-Si alloy surface showed that the initial structural state of the alloy significantly affected the mechanism of relaxation of internal stresses generated by shock-cyclic loading. The formation of orientation chaos observed in pre-homogenized alloy. Many nanoscale areas (20-50 nm wide and up to 80 nm long) of re-orientation matrix with random orientation formed on the surface of the specimen. After aging of the alloy to form a metastable b¢ phase, relaxation was due to the formation of non-crystallographic orientation bands with a high density of dislocations and ragged dislocation boundaries. It was found that the fragmentation of matrix or grain refinement was not observed during ultrasonic shock treatment of Al-Mg-Si alloy.

The possibility of changing the structure and properties of the wrought low-alloyed, inexpensive Al-Mg- Si alloy due to the use of different modes of severe plastic deformation (SPD) in combination with different types of thermal treat ments both before and after SPD has been studied. It was shown that the use of SPD at room temperature for Al-Mg-Si alloy formed a heterogeneous deformation structure which is characterized by incomplete dynamic recrystallization. The average grain size decreased from 200-500μm to 300- 500nm. SPD provoked the deformation-induced complete or partial dissolution of excess phases, regardless of the initial state of the alloy. This was accompanied by the formation of a supersaturated solid solution in the matrix. Grain refinement a nd substructure formation led to the increase of tensile strength from 207 to 391 MPa in the pre -aged samples, their elongation being reduced by 30%. The study of aging and thermal stability of the structures formed after SPD showed that the SPD processes were accompanied by the formation of microporosity which determined the limits of the accumulated strain (e5.1) and the aging temperature (Т140 °C ).

Decomposition processes of supersaturated solid solution of aluminium alloys alloyed with Sc and Zr have been studied in the work. The binary hypereutectic Al-Sc alloys, hyperperitectic Al-Zr alloys and ternary AlSc-Zr alloys were chosen. Alloys were obtained by the melt-spinning. Melts were quenched from temperatures of T = 1000 C and T = 1400 degrees C. The study of the structure of rapidly solidifyed binary Al alloys alloyed with Sc and Zr showed that the crystallization of anomalously supersaturated solid solution (T-quen = 1400 degrees C) or the crystallization with the formation of "fan" structure (T-quen = 1000 degrees C) are possible depending on the quenching temperature of the melt. The decomposition of anomalously supersaturated solid solution is continuous, with the precipitation of nano-sized spherical Al3X (X-Sc, Zr) particles of L12-ordered phase which is isomorphous to matrix. It was found that the loss of thermal stability of Al-Sc alloys is due to the loss of coherence of the strengthening Al3Sc phase. In Al-Zr alloys the loss of strength is due to the formation of a stable tetragonal DO23-ordered A(13)Zr phase. After co-alloying of Al by Sc and Zr a bimodal grained structure was observed for the hypereutectic ternary alloy (T-quen = 400 degrees C). Nano-sized grains of 50-60 nm were present on the boundaries of 1-2 mu m large-sized grains. TEM shows the formation of nanocomposite Al3Zr/Al3Sc particles. The formation of Al3Zr shell changes the nature of the interfacial fit of the particle with the matrix and slows down the decomposition during the coalescence. Ternary Al-Sc-Zr alloys have significantly higher thermal stability during aging as compared to binary Al-Sc and Al-Zr alloys.

Decomposition of supersaturated solid solution of aluminium alloys alloyed with Sc and Zr have been studied in the work. The binary hypereutectic Al-Sc alloys, hyperperitectic Al-Zr alloys and ternary Al-Sc-Zr alloys were chosen. Alloys were obtained by the melt-spinning. Melts were quenched from temperatures of T = 1000 degrees C and T = 1400 degrees C. The crystallization of anomalously supersaturated solid solution (T-quen. = 1400 degrees C) or the crystallization with the formation of "fan" structure (T-quen. = 1000 degrees C) are possible. The decomposition of anomalously supersaturated solid solution is continuous, with the precipitation of nanosized spherical Al3X (X = Sc, Zr) particles. The loss of thermal stability of Al-Sc alloys is due to the loss of coherence of the strengthening Al3Sc phase. In Al-Zr alloys the loss of strength is due to the formation of a stable tetragonal DO23-ordered Al3Zr phase. After co-alloying of Al by Sc and Zr a bimodal grained structure was observed for the hypereutectic ternary alloy (T-quen. = 1400 degrees C). Nanosized grains of 50-60 nm were present on the boundaries of 1-2 mu m large-sized grains. Transmission electron microscopy shows the formation of nanocomposite Al3Zr/Al3Sc particles. The formation of Al3Zr shell changes the nature of the interfacial fit of the particle with the matrix and slows down the decomposition during the coalescence.