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In this paper, we present an interatomic potential predicting thermal properties of phases of titanium in their temperature range of stability at zero pressure. The potential was developed within the approach proposed by A.G. Lipnitskii and V.N. Saveliev for atomic systems with metallic and covalent types of bonds, which exactly describes three-particle interactions. The parameters of the potential were optimized to the database of results of density-functional calculations and known experimental data for hexagonal close-packed phase of Ti. The developed potential correctly describe ω -Ti as the ground state at zero temperature. Prediction of the point-defect energies, stacking fault energies, surface energies, specific heat, and thermal expansion is in reasonable agreement with the experimental and density-functional data. This indicates the transferability of the potential to describe phases of titanium in a wide range of temperatures. Melting point of β -Ti predicted using the developed potential is in excellent agreement with the experimental value. For the developed potential the lowest temperature of the mechanical stability of the β phase equals to 1156 K, at which the spontaneous transition to the α phase occurs. The volume of the transformation from β to α phase is correctly predicted by the developed potential in agreement with the experimental value. MD simulations in combination with Gibbs-Helmholtz integration show that the α phase is mechanically and thermodynamically stable at any temperature up to melting temperature of the β -Ti. The constructed potential can be applied for modeling the β phase at its range of mechanical stability as well as α phase at temperatures up to melting point of the β -Ti.

The development of low-swelling radiation-resistant alloys is vital for the creation of reliable fusion reactors. In this article, we revisit the long-standing problem of very low radiation swelling in V-Ti-Cr alloys by means of DFT calculations. In particular, we study double and triple interactions of point defects such as solutes, vacancies and self-interstitial atoms in bcc V. According to our results titanium atom and vacancy are strongly attracted and in addition to pairs form highly stable triple Ti-Vacancy-Ti complexes, which are absent in the case of chromium. By using an analytic model of void growth and using calculated binding energies of point defect complexes in bcc vanadium we obtain three orders of magnitude reduction of swelling rate due to the formation of Ti-Vacancy-Ti complexes, which allows to explain experimental observations. Finally, we explain the causes of the strong attraction between titanium and vacancy using geometry and electronic structure analysis.

Titanium additions suppress the radiation swelling in vanadium alloys, but the mechanism of the suppression is debatable. It is claimed that interactions of Ti atoms with vacancies in vanadium are crucial in the suppression. In this paper we study clustering of excess vacancies in pure V and V-4Ti by molecular dynamics simulations at 700 K based on our interatomic potentials constructed earlier for the Ti-V system. For pure V the process results in the formation of a Frank sessile dislocation while the clustering in V-4Ti ends with the formation of the Ti-vacancies complexes with a specific structure. This allows us to discuss a possible mechanism of the swelling reduction in V caused by Ti alloying.

Modeling of high-speed deformation of α-Ti at a pressure of 20 GPa and a temperature of 700 K simulating the conditions of high-energy effects is carried out. The mechanisms of plastic deformation, including sliding along prismatic planes and the α-ω transition, are established. A feature of the deformation process of titanium in the considered conditions, which leads to the formation of disperse inclusions of the α-phase in the ω-phase matrix, is revealed.

A model of high-angle general-type grain boundaries is developed and grain-boundary diffusion of niobium in a Nb–Cu system is investigated using the method of molecular dynamics. The results of predictions of the effect of a copper impurity on grain-boundary self-diffusion of niobium are compared with the experimental data on diffusion annealing of multi-layered composites containing Cu/Nb boundaries. Recrystallization of polycrystalline niobium is investigated under the conditions of grain-boundary diffusion of copper.

The results of theoretical and experimental studies of the mechanisms of diffusion-controlled processes in nanostructured metals and alloys available in the literature and obtained by the authors are discussed. The molecular dynamic method was used in the context of a modified embedded-atom method was used to investigate the process of collective recrystallization of nanocrystalline titanium. An analytical description of the recrystallization kinetics has been proposed which takes into account the contributions of triple joints to the thermodynamic driving force. Methods of transmission, including high-resolution, electron microscopy were used to examine the kinetics of collective recrystallization in nanostructured titanium VT1-0. The temperature dependence and values of the activation energy for collective recrystallization have been determined. Problems of practical implementation of nanostructured unalloyed titanium in medicine are discussed.

Investigations of the features of the diffusion along grain boundaries and of the diffusion-controlled processes in submicroscopic and nanocrystalline materials produced by methods of intense plastic deformation are reviewed. To determine the parameters of the diffusion along grain boundaries and triple junctions in metals, which are independent of the results of processing of diffusion experiments based on diffusion models, results of a molecular dynamic investigation of the diffusion in nanocrystalline copper considered as an example are presented. Comparison of the features of grain boundary diffusion in submicroscopic and nanocrystalline materials produced by various methods is performed.

Grain-boundary stresses in copper for 60 symmetrical tilt grain boundaries with different orientations of the grain-boundary plane and tilt axis have been calculated by the molecular-statics method with the use of embedded-atom-method potentials of interatomic interaction. It has been established that the grain-boundary stresses are negative for grain boundaries with small excess volumes and increase approximately linearly with a buildup of the excess volume. It has been shown that the increase in grain-boundary stresses is connected with a decrease in the average coordination number of atoms, whereas pairs of closely spaced atoms in the grain-boundary core cause a negative contribution to grain-boundary stresses.

An analysis of manifestation of the effect of acceleration of creep in polycrystalline metals and alloys in the presence of grain-boundary diffusion fluxes of an impurity from an external medium (coating) is performed. The influence of the softened (due to impurity diffusion fluxes) layer thickness on the creep character in molybdenum is discussed for the case of its diffusion contact with nickel. An analysis of the effects of the regime of impurity grainboundary diffusion on the value of strain-rate sensitivity and on the behavior of grain-boundary migration as a function of external stress is made. Using submicrocrystalline nickel as an example, the influence of grainboundary state on properties of metallic materials in submicrocrystalline state is investigated. Direct measurements, theoretical calculations and indirect estimations of the differences in grain-boundary diffusion coefficients in coarse- and ultrafine-grained states are performed. The role of dispersion hardening in stabilizing the submicrocrystalline structure and improving the creep resistance is addressed, including the case where the grain-boundary fluxes of impurity atoms are forced from an external medium.

This paper presents the ternary interaction of N, H, and vacancy point defects and the nitrogen trapping ability of aluminum vacancies induced by hydrogen by means of DFT methods employed in VASP (Vienna Ab initio Simulation Package) and Abinit packages. The obtained vacancy formation energy of 0.65 eV is close to experimental values. Although the N–vacancy complex is unstable with the negative binding energy of −0.51 eV, the stability of H–vacancy–N is proved by the positive binding energy of 0.59 eV and the appearance of the orbital hybridization in the density of state (DOS) of atoms connecting to this complex. Moreover, Al vacancies can trap more than 4 N atoms, which prevents the formation of aluminum nitride and subsequently affects not only the hardness of the Al surface but also many practical applications of AlN coating.

We have calculated the binding energy using the inserted atom method for divacancies for a large number of surfaces of aluminum, nickel, copper, palladium, silver, platinum, and gold, and also in the near-surface layers. A correlation was found between the binding energies at the high-index and low-index surfaces. The transition of the calculated quantities to bulk values was tracted while successively moving the defects into the depth of the near-surface layer of the material.

The energies for migration of vacancies and adatoms and the adatom formation energy at surfaces with low indices have been calculated for aluminum, nickel, copper, palladium, silver, platinum, and gold using the inserted atom method. We have found the self-diffusion activation energies for the jumpwise diffusion mechanism with participation of both types of surface point defect.

The vacancy formation energy is calculated using the inserted atom method for faces with high and low indices and in the near-surface atomic layers of aluminum, nickel, copper, palladium, silver, platinum, and gold. The transition of the calculated quantities to the bulk quantities is traced for successive insertion of a defect deeper into the near-surface layer of the material. The relaxation contribution to the energetics is revealed for each type of surface. A correlation is seen between the energies of formation at surfaces with high and low indices.

The spalling fracture in a copper crystallite with a specific intergrain boundary under pulsed loading is modeled numerically. It is found that the grain boundary changes the parameters of nonlinear waves generated by loading and significantly affects the character of the spalling fracture.

The process of pulse-train-induced cleavage fracture in a copper crystal with grain boundary was studied by methods of computer simulation. It is demonstrated that trains of isolated compression pulses induced in the material favor the tendency to fracture propagation along the grain boundary.

The electronic structure of the Ni3Al(001) surface is calculated using the self-consistent film linearized augmented- plane-wave method. As a result, surface states both above and below the Fermi level have been found. Practically, all the occupied surface states are generated by the atoms of nickel. There is only one occupied state at the M point localized at the surface atoms of aluminium. The states above the Fermi level are mainly localized at the Al atoms of the surface layer. There are states totally generated by the atoms of aluminium. Calculated work function exceeds the corresponding values for the Ni(001) and Al(001) surfaces.

A molecular dynamics method was used to study the interaction of isolated compression pulses with the (100) and (110) free surface in a copper monocrystallite. It is shown that this may be accompanied by cleavage fracture. Parameters of compression pulses which lead to cleavage processes are determined.