Computer-aided simulation of gas adsorption processes in nanopores

A computer-aided simulation of the behavior of molecular gas-phase hydrogen in spherical nanopores was accomplished. The calculations were performed within the frame of molecular dynamics. Interaction between hydrogen molecules is described on the basis of adaptive intermolecular reactive empirical bond-order (AIREBO) potential. The interaction of gas with the walls of nanopores was calculated using the Lennard-Jones potential. The paper also contains the calculated distributions of gas density and velocities of molecules for different temperatures and pressures. The paper states that the adsorption properties of gas systems in nanopores can be described by varying the parameters of the potential of interaction with pore walls

Computer-aided simulation of gas adsorption processes in nanopores

A computer-aided simulation of the behavior of molecular gas-phase hydrogen in spherical nanopores was accomplished. The calculations were performed within the frame of molecular dynamics. Interaction between hydrogen molecules is described on the basis of adaptive intermolecular reactive empirical bond-order (AIREBO) potential. The interaction of gas with the walls of nanopores was calculated using the Lennard-Jones potential. The paper also contains the calculated distributions of gas density and velocities of molecules for different temperatures and pressures. The paper states that the adsorption properties of gas systems in nanopores can be described by varying the parameters of the potential of interaction with pore walls

Evolution of microstructure and microhardness of dispersion-hardened V-Cr-Zr-W alloy during deformation by torsion under pressure

Results of the study of the microstructural evolution and microhardness changes of dispersion-hardened V–Cr–Zr–W alloy under severe deformation during torsion on Bridgman anvils are presented. Typical structural states and mechanisms of their formation are revealed for basic evolution stages as well as appropriate microhardness values are determined. It was shown that at true logarithmic strain values (e) in the range 0.7 ≤ e 2, the anisotropic submicrocrystalline structure is observed and the formation of two-level nanostructural states was found within grains. In the strain range (e) from 3 to 6.6, submicrocrystal sizes hardly change, but changes of two-level nanostructural state parameters are observed: the nanofragment size decreases and values of elastic curvature of the crystal lattice increases

Microstructure and mechanical properties of V–Cr–Zr alloy with carbide and oxide strengthening

A comparative study of the effectiveness of carbide and oxide types of strengthening of V–Cr–Zr alloy was carried out by means of a comprehensive certification of structural-phase state parameters and measuring the mechanical properties characteristics. It has been shown that the use of chemical-heat treatment contributes to a significant increase in the thermal stability of the microstructure and mechanical properties of V–Cr–Zr alloy in comparison with carbide strengthening under the conditions of thermomechanical treatment. A controlled increase in the volume fraction of fine particles based on ZrO2, along with an increase in the concentration of oxygen in the solid solution, leads to a decrease in the rate of oxides coagulation and an increase in the thermal stability of high disperse heterophase structure. These effects contribute to the retention of high defect structural states with nonzero values of crystal lattice curvature even after high-temperature (0.67 Tmelt) anneals. The high efficiency of dispersion and substructural strengthening is a consequence of blocking dislocation slip by fine particles stabilized by oxygen in a solid solution

Influence of temperature on microstructure parameters and microhardness of dispersion-hardened V–Cr–Zr–W alloy after deformation by torsion under pressure

Study of microstructure transformation and microhardness changes of dispersion-hardened V–Cr–Zr–W alloy after severe plastic deformation by torsion on Bridgman anvils and subsequent heat treatments was conducted. Basic stages of relaxation processes were revealed: at 800°C recovery processes take place and primary recrystallization begins; at 900°C primary recrystallization intensifies; in range of 950–1050°C collective recrystallization processes activate; at 1200°C secondary recrystallization starts. Microhardness measurement and comparison of its values with structural states features were conducted. Strengthening mechanisms and their contribution at various stages of defect substructure relaxation are discussed. It is shown that increase of thermal stability of V–Cr–Zr–W alloy microstructure is a consequence of the formation of high density of thermally stable Zr (O–N–C)-based nanoparticles

Microstructure and mechanical properties of vanadium alloys after thermomechanical treatments

The results of investigation of dispersion strengthening effect on parameters of structural-phase states and characteristics of short-term strength and ductility of vanadium alloys of V–4Ti–4Cr, V–2.4Zr–0.25C, V–1.2Zr–8.8Cr and V–1.7Zr–4.2Cr–7.6W systems with different concentration of interstitial elements after optimized thermomechanical treatment mode were summarized. It was shown that for effective realization of dispersion strengthening by Orowan-type mechanism at least 25–50% of the initial volume fraction of coarse particles should be transformed into fine-disperse state and redistributed over the volume of material

Features of plastic deformation and fracture of dispersion-strengthened V-Cr-Zr-W alloy depending on temperature of tension

Influence of tension temperature on features of plastic deformation and fracture of V–4.23Cr–1.69Zr–7.56W alloy was investigated by scanning and transmission electron microscopy. It is shown that temperature increase leads t

The effect of thermomechanical treatment regimes on microstructure and mechanical properties of V-Me(Cr, W)-Zr-C alloys

The regularities of the formation of a heterophase structure in dispersion-strengthened vanadium V–Me(Cr, W)–Zr–C alloys are studied as a function of the regimes of their thermomechanical treatment. The regimes of treatment providing a substantial increase in the dispersity and homogeneity of spatial distribution of ZrC particles, temperature of recrystallization, and high-temperature (at T = 800°C) short-time strength are found in comparison to conventional treatment regimes

Two-level nanostructural states in metallic BCC-materials after high-pressure torsion in the Bridgman anvils

The results of an electron-microscopy investigation of two-level nanostructural states (submicrocrystals

Structural relaxation features of spark plasma sintered Ni3Al samples

A study of the features of relaxation processes activation in Ni3Al samples obtained by ball milling and subsequent spark plasma sintering (SPS) was carried out. The effect of the duration of the preliminary high-energy ball milling (HEBM) on the activation of structural relaxation processes at temperatures above and below the SPS temperature was revealed. It was found that at temperatures above the synthesis temperature, the main relaxation processes are associated with the activation of primary recrystallization in the most defective regions, that consist of grains of submicron sizes. It was shown that the temperature of activation of high-defect states relaxation in SPS samples of Ni3Al decreases with an increase in the duration of the preliminary HEBM