The effect of high-pressure torsion (HPT) and subsequent annealing on the microstructure, mechanical properties, and temperature stability of an aluminum alloy, the composition of which includes 92.1 wt

Despite the close study of the effect of a specimen slippage under high-pressure torsion (HPT), there is still some ambiguity in this issue. In particular, the possibility of plastic flow in the specimen under slippage conditions has not been studied. In this study the effect of a specimen slippage in dies during HPT, as well as the plastic flow pattern in the specimen deformed, were experimentally studied and analyzed. Four types of materials with different deformation capabilities were used and special specimens with an insert were manufactured. HPT was performed using constrained and unconstrained die geometry, and with varying number of revolutions. The slippage effect and the plastic flow pattern were evaluated (i) by the insert displacement, (ii) by the change in the microstructure on the specimen’s cross-section, and (iii) by the change in the specimen’s microhardness. It was found that the specimen slippage effect in dies during HPT was observed when processing difficult-to-deform materials. Despite this, plastic flow develops in the specimen as a result of multiple micro-shear deformations. Moreover, with an increase in the number of revolutions, the macro-deformation of the specimen increases. The slippage effect is more pronounced in constrained die conditions compared to unconstrained die conditions.

A study of the phase transformation in technically pure titanium under different types of deformation has been performed: upset under high pressure and high hydrostatic-pressure torsion (HPT). A set of modern methods of the study included microindentation, X-ray diffraction, transmission electron microscopy, as well as EXAFS-spectroscopy in synchrotron radiation for detailed studying a local atomic structure of phases. The correlation between the phase transformation course and the deformation method has been found. It has been shown that in contrast to pressure without a shear component, the shear deformation under high pressure at room temperature contributes to the occurrence of a high-temperature β-phase with a local atomic order different from that in the initial phase.

Symmetric and asymmetric cold rolling of steel strips was carried out. There were 5 passes at 1700 mill to obtain 0.5 mm strip thickness from 2 mm initial strip thickness. The asymmetric rolling technique—with different roll radii and equal circumferential speeds of rolls—was applied on an industrial mill for the first time: rolls have different diameters and equal circumferential speeds. The research on the microstructure and mechanical properties was carried out after each of the rolling types. It was established that steel's strength is 11–13

In this study, the effect of high-pressure torsion (HPT) on the structure, phase composition and magnetic properties of ferromagnetic MnAl-C alloy were investigated. τ-phase MnAl disks were treated in two different initial conditions: first, a disk was deformed for 20 revolutions in “as-transformed” state, and second, the deformed disk was recrystallized and then deformed for 20 revolutions again. Repeated deformation produced a coercive force of 2.0 kOe which is significantly lower than the one obtained earlier after first HPT deformation (3.7 kOe). It was demonstrated that the low level of the coercive force was associated with the failure to achieve the specified strain during HPT and with deformation inhomogeneity both in depth and along the radius of the sample. This behavior of the material during HPT was due to the high hardness of the τ-MnAl-C ferromagnetic alloy. The article suggests variants for improving the machinability of the alloy to achieve the required strain.

The possibility of the formation of a multi-metal composite from two dissimilar alloys, Ti50Ni25Cu25 and Fe50Ni33B17, upon high-pressure torsion (HPT) at room temperature has been studied. The consolidation of the dissimilar layers upon HPT has been established. It is revealed that the leading role in the consolidation of the dissimilar layers upon HPT belongs to the method of joining materials by their mutual severe plastic deformation.

Abstract—The effect of 2-h annealing at temperatures of 180–300°C on the mechanical tensile behavior of a copper/aluminum D16 alloy composite prepared by cold rotary forging of an blank 20 mm in diameter to an blank 5 and 2.5 mm in diameter (e = 2.77 and 4.16, respectively) is studied. For comparison, a composite, which comprises additional 12Kh18N10T steel fibers longitudinally arranged between a sheath and a rod, is considered. Acoustic emission testing is used to study the deformation and failure processes of composite samples during uniaxial tension. The mechanical properties and deformation of the copper–aluminum composites are found to depend on the assembling and degree of reduction of area during rotary forging. The mechanical properties of the copper/aluminum alloy composite are less sensitive to heating as compared to those of the copper/steel/aluminum alloy composite. Annealing at 300°C causes the most substantial softening of the composite samples.

Electron microscopy is used to study the evolution of microstructure of copper–aluminum composites, which takes place as the degree of reduction upon rotary swaging increases, and their conductivity is measured. The effect of reinforcing the copper–aluminum composites with steel fibers on the conductivity is studied.

The review describes a number of important recent studies in the field of physical fundamentals of severe plastic deformations (SPDs) in metals and alloys and their further systematization. Based on analyses of experimental data and theoretical approaches, we formulate for the first time three fundamental principles and seven characteristic features inherent in SPD processes. SPD physics is entirely based on the postulates of nonequilibrium thermodynamics. A solid under deformation is considered a mechanical dissipative system in which the total energy continuously decreases or dissipates, converting into other, nonmechanical, forms of energy. Within the framework of the proposed nonequilibrium evolutionary thermodynamics, it is possible to describe from a unified standpoint the evolution of the structure of defects for polycrystalline and amorphous metallic materials upon SPD. We note that the process of mechanical alloying of powders should not be completely identified with SPD processes.

To improve the balance of strength and ductility of the Al–6% Ca–8% Cu (wt %) alloy, the high-pressure torsion (HPT) deformation followed by annealing was applied. The structure of the as-cast alloy consisted mainly of two eutectics [(Al) + AlCaCu] and [(Al) + (Al, Cu)4Ca + AlCaCu]. HPT through three turns leads to the formation of a predominantly submicrocrystalline structure, refinement of eutectic particles and their more uniform distribution in the sample volume, calcium segregation from AlCuCa and (Al, Cu)4Ca particles, and supersaturation of the (Al) solid solution with copper. Such a structure provides a strengthening of the alloy by a factor of 3.5, but contributes to its embrittlement. Subsequent annealing at 400°C achieves a good balance of strength and ductility of the alloy.

A multi-metal composite was consolidated from the Ti50Ni25Cu25 and Fe50Ni33B17 alloys by room-temperature high-pressure torsion (HPT). The structural research methods used in this study were X-ray diffractometry, high-resolution transmission electron microscopy, scanning electron microscopy with an electron microprobe analyzer in the mode of backscattered electrons, and the measurement of indentation hardness and modulus of the composite constituents. The structural aspects of the bonding process have been examined. The method of joining materials using their coupled severe plastic deformation has been established to play a leading role in the consolidation of the dissimilar layers upon HPT.

The copper/aluminum alloy and copper/steel/aluminum alloy composites fabricated by rotary forging at room temperature are studied. An analysis of the calculated forging reduction ratios of the components indicates a complex process of deformation of composite workpieces during forging from an initial diameter of 20 mm to a final diameter of 2.5 mm. Rotary forging leads to significant hardening of both the copper shell and the aluminum rod and to the appearance of a nonuniform microhardness distribution in the cross section of the samples, which levels off with increasing reduction. The mechanical properties of both composites are comparable after forging to a diameter of 5 mm: the yield strength and the ultimate tensile strength are 355–370 and 390–395 MPa, respectively, at a relative elongation of 2–3%. A consistent decrease in the sample diameter to 2.9 mm does not cause a noticeable change in the strength properties of the composites and decreases the ductility of the copper/steel/aluminum alloy composite material.

A systematic study of structure and hardening of two‐phase Al–8% Ca, Al–10% Ce, and Al–10% La eutectic aluminum alloys under high‐pressure torsion (HPT) has been carried out. HPT leads to an increase in microhardness as a result of the formation of a nanocrystalline structure with a high density of crystal defects in the Al–8% Ca alloy and a nano‐ and submicrocrystalline structure with a low density of crystal defects in the Al–10% Ce and Al–10% La alloys, as well as the eutectic particle refinement in all alloys. The predominant crystallite sizes after HPT through five turns are 70–210, 60–120, and 25–45 nm, respectively, in the Al–10% La, Al–10% Ce, and Al–8% Ca alloys. The change in the shape of the curve of the microhardness distribution over the samples’ surface with an increase in the number of turns from 1 to 5 is different for three alloys. The results demonstrate the ultrafine‐grained microstructure development varied depending on the binary alloy systems. Initial as‐cast eutectic particles have a significant effect on the structure and hardening of alloys through their morphology, volume fraction, hardness, and orientational ratio with the aluminum base.

The effect of cryogenic temperatures of deformation in a Bridgman chamber via severe plastic deformation by torsion under a high quasi-hydrostatic pressure at temperatures of 293 and 77 K on the structure and mechanical properties of commercial (low-alloy) titanium is studied. Transmission electron microscopy is used to perform a detailed statistical analysis of the structure of titanium with different contents of microalloying elements.

The experimental heat resistant alloy Al-3.3Cu-2.5Mn-0.5Zr (wt%) has been manufactured using the method of electromagnetic casting (EMC) followed the high-pressure torsion (HPT) treatment. The HPT-deformation leads to the formation of nano- and submicrocrystalline structures in aluminum alloy with increased dislocation density. The predominant size range of crystallites was 80-250 nm. A change in the structure of aluminum alloy as a result of HPT leads to a multiple increase in microhardness which is about 2-time higher comparing with cold rolled strip (220 vrs. 120 HV). Annealing of the HPT-processed aluminum alloy up to 250 degrees C doesn't decrease the microhardness but after annealing at higher temperatures significant softening takes place.

Ferromagnetic alloys of the Mn-Al system are promising materials for permanent magnets and details of electric motors. Deformation methods of processing these alloys allow obtaining high magnetic properties, however, they are still not well researched. In the current study the effect of the tau-MnAl alloy structure obtained by severe plastic deformation on the phase composition, structure, and magnetic properties gained during subsequent annealing is investigated. It was shown that a twinned structure is preferable for recrystallization (in terms of recrystallized volume) than a dislocation one. The largest coercive force of 3.7 kOe was reached in the current investigation after deformation by 20 revolutions (epsilon approximate to 6.83). Subsequent annealing led to a drastic fall in coercive force due to vanishing of defects (dislocations and nanotwins) acting as sites of domain wall pinning. (C) 2021 Elsevier B.V. All rights reserved.

The influence of cold rotary forging on the mechanical properties of the Cu/Al–10% La composite, depending on the billet’s reduction ratio, has been studied. The billet was forged from an original diameter of 20 mm to a final diameter of 2.5 mm (e = 4.16). It is shown that the formation of a predominantly subgrain structure with a high density of dislocations in a copper shell, and a predominantly ultrafine grain/subgrain structure in an aluminum rod provides an approximately two-fold increase in the strength of the composite material compared to its components. To clarify the mechanisms of deformation and fracture of the composite samples under tension, the acoustic emission technique was used. It is shown that by choosing the temperature of post-deformation annealing, it is possible to achieve the required balance between strength and plasticity of the composite samples. The electrical conductivity and coefficient of linear thermal expansion of the composite samples have been measured.

The crystallization mechanisms and kinetics in amorphous Ti50Ni25Cu25 alloy produced by different methods of amorphization have been studied by X-ray diffraction at room temperature and in situ synchrotron diffraction upon heating up to 823 K. One of the amorphous states was obtained by melt quenching (MQ) at a cooling rate of approximate to 10(6) K/s. The other amorphous state was realized in a polycrystalline alloy of the same composition by high pressure torsion by four revolutions of the movable anvil (HPT4). Differential scanning calorimetry was used to determine the temperatures of crystallization and glass transition, as well as a change of the thermal effect as a function temperature. It is shown that the amorphous states under consideration substantially differ in the mechanisms and temperature parameters of crystallization. The amorphous phase produced by HPT4 was found to be less stable with respect to heating than the amorphous phase obtained by MQ. The origins of the difference in the crystallization kinetics of the amorphous phases obtained by MQ and HPT4 are discussed.