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The paper investigates the evolution of the structure and properties of low-alloy dispersion-hardening alloys based on the Cu–Zr, Cu–Cr, and Cu–Cr–Zr systems under high-rate deformation (~105 s–1) by dynamic channel angular pressing (DCAP) and subsequent annealing (aging) at 200–700°C. The effect of alloying with the microadditives Cr (0.09–0.22%) and Zr (0.04–0.20%) in achieving high hardness of copper with a submicrocrystalline structure obtained by DCAP is studied. The effect of DCAP and subsequent aging on the electrical conductivity of alloys is studied. The sequence of decomposition processes of a copper-based α solid solution with the precipitation of nanoscale particles of the second phases and recrystallization is determined. It is shown that the role of zirconium is due to the precipitation of Cu5Zr phase nanoparticles during DCAP and subsequent annealing on dislocations and subboundaries, their fixation, and reduced mobility, as a result, the process of formation of recrystallization centers slows down, which requires rearrangment (restructuring) of the dislocation structure. [ABSTRACT FROM AUTHOR]

The evolution of the structure of chromium–hafnium bronze under high-speed severe plastic deformation by dynamic channel-angular pressing (DCAP) and subsequent annealing has been studied. It is shown that fragmentation of the structure under DCAP occurs predominately through the twinning mechanism, especially upon two passes. In this case, significant strengthening occurs and the microhardness increases to 1750 MPa. When bronze is annealed, additional strengthening occurs due to the precipitation of Cu5Hf and Cr particles. The structure of bronze after DCAP has high thermal stability, and maximum hardness is achieved after annealing at 400°C. The strengthening and thermal stability of the structure in chromium–hafnium bronze is higher than in hafnium bronze. [ABSTRACT FROM AUTHOR]

The mechanical properties of alloys Cu–0.03 wt % Zr and Cu–0.10 wt % Cr with a submicrocrystalline structure formed after dynamic channel angular pressing and subsequent annealing. The properties of the alloys were studied under conditions of shock compression with a pressure of 4.7–7.0 GPa and a deformation rate of (1.3–3.2) × 105 s–1. It is shown that grain size refinement from 200–400 to 0.3–1.0 μm increases the dynamic elastic limit and the dynamic yield strength of the Cu–0.03% Zr alloy by factors of 1.9 and 1.8, respectively. At the same time, the spall strength is reduced by a factor of 1.4. Subsequent annealing at 400 and 450°C can increase the characteristics of the elastic–plastic transition by factors of 3.0 and 3.7, respectively. This elevates the spall strength to the level of a large crystal analogue. It is determined that the process of dispersing the Cu–0.10% Cr alloy structure to 1.0–5.0 μm leads to an increase in the spall strength by a factor of 1.5 with respect to this value in the coarse grained state, while the dynamic elastic limit and the dynamic yield strength are increased by factors of 3.7 and 2.6, respectively. [ABSTRACT FROM AUTHOR]

In this paper, we study the structure evolution of hafnium bronze undrer annealing after hardening and severe plastic deformation by two methods: dynamic channel-angular pressing (DCAP) and high-pressure torsion (HPT). Severe plastic deformation of hardened bronze is shown to lead to significant hardening. Under the annealing of bronze, additional hardening occurs due to the precipitation of Cu5Hf particles. The bronze structure after severe plastic deformation has a high thermal stability; the maximum hardness is achieved upon annealing at 400°C after DCAP and 300–400°C after HPT. [ABSTRACT FROM AUTHOR]

The high-rate convergence of copper cylindrical shells with a diameter of 48 mm and a wall thickness of 4 mm is studied at various intensities of explosive loading. Two structural mechanisms of the loss of stability of the radial deformation front are described. A diagram of structural changes reflecting the successive stages of the convergence process is presented. An interrelation is found between the number of protrusions on the shell surfaces during their corrugation at the intensity of explosive loading. It was found that high-rate longitudinal deformation during convergence has a pulsating character. It was found that the temperature rises to ~500°С in the center of the converged shell and that it can be higher than 1000°С at a high rate of spall-pore collapse. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of chromium–nickel austenitic stainless steel fabricated by selective laser melting using a Realizer SLM100 3D printer have been investigated in this work. The structure of the studied specimens has been formed by the complete melting of the initial powder and high-speed cooling of the melt. Cooling of the melt initially leads to the formation of δ ferrite, and then, polymorphic δ → γ transformation results in the formation of the final austenitic structure. The structure of δ ferrite which formed during melt crystallization has been found to exhibit a clear pattern of periodicity. The periodicity depends on the parameters of the melting process, such as the distance between neighboring bands formed during laser-beam traveling (intertrack distance) and the step of platform feeding (distance between layers). The polymorphic δ → γ transformation takes place by a disordered mechanism and no austenite texture forms. However, some structural heredity remains. It can be seen in the orientational relationship between some austenite grains and δ-ferrite grains. The steel fabricated by laser melting is shown to have high mechanical properties such as the yield strength, the ultimate tensile strength, and the tensile elongation at a strain rate of 10–2 s–1, which are 320, 765 MPa, and 50%, respectively. The yield strength and ultimate tensile strength of the specimens under dynamic compression by the Hopkinson–Kolskii technique at an average strain rate of 103 s–1 are 550 and 945 MPa, respectively. [ABSTRACT FROM AUTHOR]

Using high-resolution scanning and transmission electron microscopy methods, the morphological and size characteristics of the structural components of the composites synthesized on the basis of aluminum with a graphene microadditive in a commercial aluminum melt under a layer of molten salt are studied. An experiment on the dynamic compression of a composite by the Kolsky method was performed, the evolution of a cast structure during high-rate deformation is studied, and mechanical characteristics in the range of deformation rates έ = 1.8–4.7 × 103 s–1 were measured. The dynamic characteristics of the composite were measured under conditions of loading with planar shock waves (έ = 5 × 105 s–1) for the first time. The dynamic properties of the composite are compared as functions of the graphene content in the aluminum matrix. [ABSTRACT FROM AUTHOR]

It is shown that initial treatment (quenching or annealing) has a significant effect on the evolution of the structure of hafnium bronze upon dynamic channel-angular pressing (DCAP). Upon annealing, hafnium becomes bound into particles of the intermetallic compound Cu5Hf, and the annealed samples are only insignificantly strengthened upon DCAP. Upon quenching, Hf remains in the solid solution, and the strengthening effect upon DCAP is much greater. Twinning becomes the main deformation mechanism for quenched bronze upon DCAP. [ABSTRACT FROM AUTHOR]

The deformation structure in copper that forms upon the convergence of a massive cylindrical shell into a cylinder is studied in this work. The shell in the deformation zone was subjected to high-speed deformation (~104 1/s) with large values of true strain (e varied from 0.8 to 2.0). It is shown that two types of structures were formed under deformation: regions containing disperse grains with high-angle boundaries and twins and regions with deformation cells having low-angle boundaries. It is found that the twins that arose at the early stages of deformation are distorted upon further deformation: their rectilinear boundaries are bent, the orientation relationships with the matrix are violated, and high-angle boundaries of arbitrary orientation are formed. [ABSTRACT FROM AUTHOR]

Abstract—The dynamic properties of commercial copper (99.8 wt % purity) with a submicrocrystalline and nanocrystalline structure obtained by high-strain-rate deformation using the dynamic channel-angular pressing (DCAP) method have been studied in this work. The tests were carried out under conditions of shock compression at a pressure of 5.6−6.8 GPa at a strain-rate of (0.9−2.0) × 105 s–1. The analysis of the evolution of the structure and mechanical properties, namely, the dynamic elastic limit, dynamic yield stress, and the spall strength of copper before and after DCAP in different regimes, made it possible to evaluate the influence of the dispersity and imperfection of the crystal structure on its resistance to the high-strain-rate deformation and fracture. It has been shown that the grain refinement from 100 to 0.5−1.0 μm increased the dynamic elastic limit and the dynamic yield stress of copper by six times, but only slightly decreased the spall strength. The further refinement of the structure (up to 0.05−0.40 μm) increases the spall strength of copper by 1.4 times as compared to its value in the initial coarse-grained state. [ABSTRACT FROM AUTHOR]

A number of regularities of phase and structural transitions in an economically iron and nickel doped aluminum alloy with eutectic-forming elements (nikalin) at high shear strains under pressure have been determined in this work. The structural evolution of nikalin, in particular, the change in the morphology and sizes of its structural components, such as solid Al solution grains and eutectic aluminides Al9FeNi, was studied by scanning and transmission electron microscopy. The torsion of nikalin under high pressure was determined to result in the formation of a strengthened composite material with a submicrocrystalline Al matrix and dispersed (1.5–2.0-µm) particles of transition–metal aluminides. Kolsky dynamic compression and plane shock wave loading experiments were performed, and the mechanical behavior of nikalin with different structures was studied within a strain rate range of 10–4–105 s–1. The dynamic characteristics of nikalin were compared with the mechanical properties determined in static tests. [ABSTRACT FROM AUTHOR]

Metallography has been used in this study to investigate copper samples cut from cylindrical shells collapsed under shock wave loading. Spallation phenomena (either the shell is divided into concentric rings, or a wide zone with spallation cavities and cracks is formed), which occur in shells under shock wave loading are considered. High-rate deformation during inertial convergence heals pores and cracks. Traces of healing remain in the microstructure. Various cases of nonradial convergence, when a stable circular deformation front is lost, are observed. Bends appear on the thin-walled shell and the shell crumples during its converging. Periodically arranged protrusions form on the inner surface of the thick-walled shells. They subsequently join together, converging to the center of the shell. A wave-shaped relief, protrusions, dents, and corrugation on the outer surface indicate the loss of stability. [ABSTRACT FROM AUTHOR]

A bulky copper cylindrical shell with an internal diameter of 118 mm and a wall thickness of 5.9 mm has been exposed to an explosion of a cylindrical explosive charge uniformly distributed around it. A cylinder with a diameter of 57-58 mm has been obtained as a result of high-speed deformation caused by the explosion. A metallographic analysis of the cylinder structure shows that the shell collapses under the influence of axially symmetric radial deformation, which is accomplished by both twinning and sliding mechanisms. It is determined that axial deformation occurs along with the radial deformation. The microstructure of the cross-section consists of three zones. A wide annular deformation zone is formed on the outside, an annular recrystallization zone is formed closer to the center, and a circular region with a dendritic structure is formed at the center. The presence of dendrites indicates that the temperature at the boundary of this region reaches the melting point of copper. The temperature change along the radius of the cylinder has been calculated. [ABSTRACT FROM AUTHOR]