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.

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

The mechanical properties of alloys Cu–0.03 wt

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 Cu 5 Hf 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.

Composites based on Al-Mg alloy, reinforced with graphene nanofilms, were obtained by in situ synthesis under a layer of salt melt. Using SEM and HRTEM, the morphological and dimensional characteristics of the structural components of composites with different contents of graphene were studied. An experiment on dynamic compression of composites by the Kolsky method was carried out, dynamic properties were measured, and the evolution of a cast structure during high-speed deformation was considered. For the first time, the dynamic properties of composites under loading by plane shock waves have been determined. The dynamic properties of aluminum matrix composites are compared depending on the properties of the non-reinforced alloy.

The structure and mechanical properties of composites consisting of a metal matrix based on aluminum and its alloys of different compositions (AA-3003 and AA-5154) and graphene synthes sized in situ under a layer of molten salts were investigated depending on the chemical composition and grain size of the matrix. Aluminum matrix composites of three compositions were studied in as-cast coarse-grained, deformed fine-grained (grain size < 1 mm), and deformed sub microcrystalline (grain size < 1 μm) states in order to compare the structural characteristics of composites with different grain sizes. The composites were subjected to deformation with a split Hopkinson (Kolsky) bar and to dynamic-channel angular pressing. The hardness and dynamic mechanical properties of the composites were measured at strain rates ε˙ from 1.8 − 4.7 × 103 to 1.6 − 2.4 × 105 s−1. It was found that grain refinement induced a sharp increase in the hardness of composites with various compositions (by a factor of 1.6–2.6). A correlation of the elastic-plastic properties of the aluminum matrix composites with the grain sizes and chemical compositions of the matrices was established. A transition from coarse-grained to sub microcrystalline structure was shown to improve the elastic-plastic properties on average by a factor of 1.5. It was proved that the reinforcing effect of graphene increased with the decreasing grain size of the matrix. Mechanisms of reinforcement of the aluminum matrix composites using graphene were proposed.

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.

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 × 10 3 s –1 were measured. The dynamic characteristics of the composite were measured under conditions of loading with planar shock waves (έ = 5 × 10 5 s –1 ) for the first time. The dynamic properties of the composite are compared as functions of the graphene content in the aluminum matrix.

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 10 3 s –1 are 550 and 945 MPa, respectively.

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.

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 Cu 5 Hf, 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.

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 (~10 4 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.

An experiment is performed for explosive convergence (collapse) of a cylindrical shell of low carbon steel with a ferrite-perlite structure. It is revealed that during ultra-rapid heating caused by high-speed deformation austenite formation occurs in an unusual sequence: first, free ferrite is converted, then pearlite. The decrease in free ferrite transformation temperature is explained by action of high pressure, as well as by varying degrees of heating steel structural constituents. An effect of barothermal quenching is observed, as a result of which a pearlite-martensite structure forms.

The structural mechanisms of buckling and the deformation behavior of copper and steel cylindrical shells (pipes) during collapse under the action of an explosion are studied. The dependence of deformation behavior on the transverse dimensions of the shell and properties of the loaded material is described. It is established that the stability of radial collapse depends on absolute dimensions of the shell rather than relative dimensions, with the collapse of large-diameter shells occurring more stably. It is demonstrated that the collapse stability is violated due to the formation of a characteristic pattern of localized strain in the sample, consisting of homogeneous, orderly arranged structural elements whose dimension depends little on the material properties and experimental conditions. A criterion for stable radial collapse that relates the characteristic dimensions of the structural element of localized strain and the shell radius is proposed.