Russian Metallurgy (Metally)最新文献

Abstract—A hypereutectic Al–8Ca–2Mn–1Ni–0.3Fe–0.3Zr (composition is given in weight percent) alloy prepared by casting in an electromagnetic crystallizer is subjected to hot rotary swaging (RS) from an initial diameter of 14.5 mm to a final diameter of 5.2 mm. RS is found to lead to the formation of an ultrafine grain–subgrain microstructure. The alloy subjected to RS exhibits a yield strength, ultimate strength and relative elongation of 269 MPa, 342 MPa, and 4.5%, respectively; in this case, fracture is completely ductile and the linear thermal expansion coefficient is low, at the level of traditional hypereutectic silumins.

Abstract—The deformation and failure of two types of three-layer metallopolymer composites have been analyzed. The outer layers of these composites are thin sheets of VT23 high-strength titanium alloy, and the inner layers are made of carboplastic or organic plastic. Failure staging of laminated composites has been considered. The properties of the composites have been compared from specific characteristics, namely, from ratios of strength parameters and Young modulus to specific weight. It has been shown that the load-carrying capacity of the composite consisting of highest specific strength materials (titanium + carboplastic) may be lower than that of the composite with high deformation performance (titanium + organic plastic).

Abstract—The cross-hardening diagrams of titanium nickelide, the martensitic inelasticity diagram of which has no yield plateau, is found to converge into a single curve as the stresses increase. This curve is equidistant to the direct transformation diagram and is located significantly higher than the initial martensitic inelasticity diagram. These results suggest that the cross hardening may be substantially higher (by more than 50 MPa) than that generally accepted earlier.

Abstract—The influence of the structure and texture formed by deformation treatment under different conditions on the mechanical properties of pure magnesium is investigated. The strength and plasticity of pure magnesium is shown to depend not only on grain size, but also on texture. For example, equal-channel angular pressing (ECAP), which causes a sharp inclined basal texture, leads to significant softening of pure magnesium as compared to the pre-ECAP extruded state at a significant increase in plasticity. In the case of rotary swaging (RS), magnesium has the highest strength after deformation at 350°C, which brings about strong grain refinement and a texture with the highest fraction of a nonbasal component. A further decrease in the RS temperature and an increase in the strain, which leads to further grain refinement and a decrease in the fraction of a texture-free component, decrease the yield strength of pure magnesium at a significant increase in its plasticity. The best combination of mechanical properties, specifically, a high strength (σ_0.2 = 148 ± 1 MPa, σ_u = 218 ± 3 MPa) and plasticity (δ = 19.0 ± 0.6%), is achieved after RS at 300°C and a true strain ε = 2.77 due to the formation of a favorable structure and texture.

Abstract—The structure, phase composition, mechanical properties, and corrosion resistance of the Ti–10 at % Nb–(1–3 at %) Mo alloys subjected to cold rolling and water quenching from temperatures of 750, 800, and 850°C are studied. The rolled alloys are found to consist of the α and β phases; as the molybdenum content increases, the content of the β phase increases. After quenching from all considered temperatures, the alloys mainly consist of the α" phase; in this case, after quenching from 750°C, insignificant amounts of the α, β, and ω phases are present. The heating before quenching from 750°C is shown to slightly affect the grain size. As the temperature increases to 800 and 850°C, the recrystallization and grain growth occur. Quenching from the temperature above 800°C leads to the increase in the plasticity and decrease in the strength. The Ti–10 at % Nb–1 at % Mo alloy quenched from temperatures of 800 and 850°C is found to demonstrate the minimum Young’s modulus (62–63 GPa) and high strength properties.

Abstract—A technique for numerically simulating the influence of zirconium hydride orientation on deformation and local strain distribution in tubes made of Zr–Nb–Sn–Fe (E635) zirconium-based alloy is described. Simulation has been performed by the finite-element method embedded in the ANSYS software package by taking into account the crystal texture in the material at room temperature. It has been shown that radially oriented hydrides cause sharper stress variation than those oriented tangentially. It has been confirmed that the dependence of von Mises maximal stress on hydride orientation factor F_n in the tube is S‑shaped, which indicates the presence of the ductile-to-brittle transition in the interval F_n = 0.20–0.35. Simulation results agree with experimental data, so that the suggested technique may be considered applicable for predicting the mechanical properties of hydrogenated tubes made of zirconium alloys.

Abstract—The efficiency of acoustic emission (AE) for detecting defects in plastic parts fabricated by fused deposition modeling and subjected to load is investigated. Specimens of acrylonitrile–butadiene–styrene (ABS), polyethylene terephthalate glycol (PETG), and polylactide (PLA) are tensioned to failure, and discrete AE signals are simultaneously recorded. The time dependences of the number of AE signals and their activity and the amplitude distributions of AE signals are analyzed. A correlation is revealed between changes in the AE flow parameters and the formation of cracklike defects, the presence of which is confirmed by optical microscopy.

Abstract—The structure, deformation behavior, and tensile properties of soft magnetic alloy 2NSR, 30KSR, and 84KKhSR ribbons produced by melt spinning are studied. The ultimate tensile strength of the ribbons is shown to exceed 1000 MPa at a small relative elongation ε ≈ 1%, and the elastic modulus is 100 GPa. Strain component distribution fields are constructed and analyzed. The characteristic structural-scale levels of deformation in the alloy ribbons are discussed.

Abstract—The athermal and deformation-induced martensitic transformations in a titanium nickelide-based alloy are considered. For this purpose, specimens are subjected to tensile deformation at various degrees and then heated to measure their sizes and to perform X-ray diffraction analysis of the phase composition and microstresses in the B2 phase. The martensitic transformation is found to be thermoelastic during deformation up to the first critical degree. Above this deformation, an intensive increase in microstresses occurs, which is associated with shape changes in the material due to dislocation formation and slip. This mechanism competes with and begins to suppress the martensitic transformation mechanism above the second critical strain. Here, the martensitic transformation acquires characteristics of an explosive transformation mechanism.

Abstract—Effect of a barrier copper coating deposited on reinforcing carbon fibers on their compatibility with an aluminum matrix (wrought AD31 alloy of the Al–Mg–Si system) is studied. The coating was deposited by galvanic deposition from an acid or alkaline electrolyte at room temperature. No coating has been deposited onto SiC fibers. Samples have been fabricated by spontaneous impregnation at temperatures of 700–950°C in vacuum at a residual gas pressure of 0.1 Pa. The microstructure of the fiber–matrix bonding regions is studied. The coating formed from an alkaline electrolyte is shown to provide better wetting of the fibers by the matrix melt.