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The temperature and amplitude dependences of internal friction in hybrid composites consisting of unidirectional carbon fibers and glass tissues in a T-107 molten epoxy matrix have been studied. From the high-frequency portion of the internal friction background with regard to its low-frequency one, the energy of formation and migration of vacancy-like defects in an amorphous matrix of glass fiber- and carbon fiber-reinforced composites has been estimated.

The nucleation and propagation of a shear band in a metallic iron glass model under uniaxial tension were studied by analyzing the quadratic nonaffine displacements of atoms. The evolution of its atomic structure was performed using statistical geometric analysis based on the construction of Voronoy polyhedra. A model was proposed based on notions about the formation of an elastic stress field equivalent to the field of a dislocation located in the area of a minimum gradient in the concentration of local shear-induced transformation centers for the nucleation and motion of a shear band.

We have studied the stability of ultradispersed diamond and carbon nanotube suspensions in water and aqueous solutions of various salt electrolytes. The results demonstrate that, in the course of coagulation and sedimentation, the particles in suspension become separated into size fractions and form agglomerates several orders of magnitude greater in size than the parent particles, and that the dependence of the suspension concentration on storage time has a linear portion. The sedimentation process in the electrolyte solution-based suspensions proceeds until an almost zero concentration of fine particles is reached. We have determined the settling time of the particles in the suspensions, which determines their stability, and evaluated the porosity of particle conglomerates. The feasibility of suspension redispersion after sedimentation has been examined. Resonication of the suspensions has been shown to restore the particle concentration and size.

Patterns of the generation of nanocluster icosahedral substructures of pure iron metallic glass upon quenching a melt with two competing processes, athermal nucleation and the growth of polytetrahedral local formations and their decomposition under the impact of thermal fluctuations, are investigated by means of molecular dynamic simulation.

By differential scanning microcalorimetry, measurements of specific electrical resistivity, and X-ray crystal structure analysis, a spectrum of structural transformations during isochronous heating of thinfilm metal glasses of Ni60Nb40 alloy over the range of temperatures of 20–950°C is investigated.

The laws of atomic restructuring in the Cu80Zr20 metallic glass during melt quenching are studied by molecular dynamics simulation using statistical-geometrical analysis based on Voronoi polyhedra and cluster analysis. The morphology and size distribution of polyhedral nanoclusters in the glass structure are investigated.

Within the framework of the method of molecular dynamics and statistic geometrical analysis, laws governing the formation of the structure of a percolation cluster consisting of interpenetrating and mutually contacting icosahedra have been studied in the process of iron vitrification. The results of an analysis of the morphology of clusters consisting of only interpenetrating icosahedra and of the nature of their joining into a percolation cluster are presented.

The results of molecular dynamics simulation of the process of atom-by-atom growth of palladium nanoparticles are presented. The structures obtained for the Pdn clusters agree well with the results of the first-principles calculations. The low-symmetry atomic configurations for the structure of the Pd4 and Pd13 clusters have been obtained using the semiempirical potentials of the interatomic interaction for the first time.

Features of the formation of a percolation cluster structure composed of interpenetrating and contacting icosahedra during the glass transition in an amorphous Ni60Ag40 alloy have been studied using the molecular-dynamics method and statistical geometric analysis. Data on the morphology of clusters composed entirely of the interpenetrating icosahedra and on the character of their conjugation in the percolation cluster are presented.

This paper reports on the results of the molecular dynamics simulation of isothermal and isochronous annealings of binary clusters in the Cu-Ni and Cu-Pd systems. The specific features of the formation of the structure are investigated as a function of the component ratio and the cluster size. It is revealed that the Cu-Ni and Cu-Pd clusters have low and high tendencies toward amorphization, respectively. This is explained by different ratios between the atomic sizes in compositionally ordered systems.

Features in the evolution of the atomic structure of the Ni60Ag40 alloy upon quenching from a liquid disordered state were revealed within the molecular-dynamics method using many-particle potentials of interatomic interaction, calculated within the embedded atom method. It was shown that the structural stabilization of the amorphous Ni60Ag40 phase during the glass transition occurs due to the formation of a percolation cluster of interpenetrating and contacting icosahedra with nickel and silver atoms at vertices and preferentially nickel atoms at centers.

The structure of an fcc(001)/fcc(001) interphase boundary in a “nickel hemispherical crystal nanoparticle-palladium crystal substrate” system is investigated using molecular dynamics simulation with multiparticle potentials calculated in the framework of the embedded-atom method as a function of the angle of rotation of the nanoparticle. Relaxation transformations are found to occur in a component of the system under investigation with a larger lattice parameter. It is demonstrated that, under given annealing conditions, the system is characterized by a size dependence of the angle of rotation of a nanoparticle: the annealing leaves the location of large islands virtually unchanged but brings about a rotation of small nanoparticles into a parallel orientation or an orientation with a local energy minimum.

Crystallisation processes of amorphous Cu-film on Pd(001) substrate have been investigated by molecular dynamics method. It has been established that the formed structure has tetragonal distortions; the elastic stresses caused by dimensional misfit of crystal lattices of the substrate and the film lead to the formation of complex defect structure changing during the annealing.

Molecular-dynamics simulation based on many-particle potentials calculated in terms of the embedded-atom method was performed to study growth of Ni films on singular (001), (110), and (111) surfaces of a Pd single crystal at a temperature T = 1000 K. Upon the growth of a Ni film on (001)Pd and (110)Pd surfaces, there is formed a heterostructure consisting of a Pd substrate, a single-layer epitaxially stabilized solidsolution phase, and a film of an Ni-Pd solid solution. At the initial stages of the film growth, the lattice misfit is compensated via elastic deformation; with increasing average thickness of the film, there occurs a relaxation of the elastic deformation: in the (001)Pd-Ni heterosystem, via the formation of misfit dislocations; in the (110)Pd-Ni heterosystem, via misfit dislocations and point defects (in the [\(1\bar 10\)] direction) as well as via partial dislocations (in the [001] direction). Upon the growth of an Ni film on the (111)Pd surface, no intermixing of the components occurs; already at the initial stages of growth, the islands (clusters) are not deformed; the matching at the interphase boundary is incoherent.

An isothermal kinetic diagram for the beginning of homogeneous nucleation is constructed using the molecular-dynamics model of an instantaneously supercooled iron melt near the icosahedral percolation transition temperature identified with the glass transition temperature T g . This diagram is compared with the theoretical one calculated using quantitative information obtained by analyzing the kinetics of the initial stage of growth of supercritical nuclei at temperatures higher than T g . A satisfactory coincidence of the theoretical curve with computer simulation data at temperatures higher than T g and substantial disagreement with these data below T g , where crystallization is necessarily preceded by the formation of an icosahedral percolation cluster, demonstrate the substantive influence of an icosahedral substructure on the nucleation rate predicted by the classical theory.

A molecular dynamic model for instantaneously undercooled iron melt has been applied to model the isothermal annealing of the stable percolation clusters. They contain mutual penetrating and contacting icosahedra with atoms at the vertices and centers. Such stable clusters form only below the critical temperature Tg ~1180 K. We identify Tg as the glass transition temperature. It is established that the time when a homogeneous nucleation starts is minimal for Tg. The stable icosahedral percolation clusters do not form above Tg. The proposed quantitative model describes the atomic mobility in metal glasses, where root-mean-square atomic displacement is the sum of contributions from both linear (Einsteinian) and logarithmic terms, associated to irreversible structure relaxation. The activation parameters of the model change abruptly at the icosahedral percolation transition.

The paper develops concepts of the structure of pure amorphous metals and atomic mechanisms of its formation. It is shown that a stable percolation cluster of interpenetrating and contacting icosahedra whose vertices and centers are occupied by atoms is formed under the conditions of isothermal annealing of instantaneously supercooled iron melt only below the critical temperature ∼1180 K identified with the glass transition temperature. The duration of isothermal annealing up to the formation of the icosahedral percolation cluster does not exceed ∼1.5 × 10−11 s at 900–1180 K. The time of the beginning of homogeneous nucleation was found to be minimum at the critical temperature above which stable icosahedral percolation cluster did not form. Arguments are provided in favor of the assumption that the formation of icosahedral percolation cluster interferes with the beginning of crystallization. A quantitative model is suggested to describe the diffusion mobility of atoms in metallic glasses. In this model, the mean-square displacement of atoms is represented as the sum of the contributions of the linear (Einstein) and logarithmic components. The latter appears because of irreversible structural relaxation. The icosahedral percolation transition was shown to change the activation parameters of the model jumpwise.

It is shown on the basis of the model of iron with the Pak-Doyama paired potential of interatomic interaction in the framework of the molecular dynamics method that structural stabilization of the amorphous phase of pure iron during hardening from melt is ensured by the formation of a percolation cluster from mutually penetrating and contacting icosahedrons with atoms at vertices and centers.

The atomic mechanisms and kinetics of self-diffusion of Pd adatoms on a single-crystal Pd(001) surface are investigated using molecular dynamics simulation. It is shown that the migration of Pd adatoms on the Pd(001) surface predominantly occurs through the relay-race mechanism with the participation of substrate atoms. The activation energy for an elementary event of relay-race self-diffusion is calculated from the kinetic equation describing the change in the concentration of surface adatoms labeled at the initial instant of time.

Molecular dynamic simulation with multiparticle potentials calculated by the embedded-atom method shows that a [(001)Pd–75% Pd–25% Ni solid-solution monolayer–79% Pd–21% Ni solid-solution monolayer] heterostructure is formed due to structural–morphological transformations and diffusion exchange between Ni and Pd atoms in a system of the Ni monolayer on the (001)Pd singular surface. The formation of two adjacent solid-solution monolayers ensures their coherent connection by means of elastic deformation and explains the pseudomorphism of subnanofilms with large dimensional discrepancy between the components of the original heterostructure.

Spontaneous twisting of (NH4)2SO4 crystals at the phase transition from the paraelectric phase Pnam to the ferroelectric phase Pna2 (TC = 223 K) was studied using the method of low-frequency torsion pendulum. It is shown that the macroscopic twisting of samples is caused by the rearrangement of ferroelastic twins with the {011} and {031} twinning planes existing in both the paraelectric and ferroelectric phases. A model interpreting the effect of the spontaneous twisting below the ferroelectric Curie point is proposed.

Using a torsion pendulum, the features of spontaneous twisting of several ferroelastic crystals at a temperature variation near the phase transition points have been studied as a function of a crystallographic orientation, a thermal and mechanical history, and an external static shear stress. It was assumed that a torque arises at the Curie point because of the specific domain structure organization resulted in the predominant formation of that certain domain types.

It is shown that a system of classical particles considered in a molecular dynamics model with Pak-Doyama pairwise interatomic potential adequately describes not only the various structural states of iron (melt, bcc crystal, metal glass) but also the complex self-organization processes occurring in first-and second-order phase transitions (crystallization and vitrification, respectively). When the temperature is varied at a constant rate of 6.6×1011 K/s, crystallization sets in from both the amorphous and the liquid state; at a rate of 1.9×1012 K/s, crystallization is observed only in the amorphous state; and when heated at a rate of 4.4×1012 K/s, the model amorphous iron transfers to the liquid state without crystallization. The energy of homogeneous formation of a crystal nucleus in the bulk of the amorphous phase of iron is calculated to be ∼0.71 eV under the assumption that there is a spectrum of activation energies.

A quantitative model of visco-plastic damping induced by structural relaxation of metallic glasses is developed. The model is shown to be consistent with the experiment.

The results of research into the interaction of 0.04 mm diameter gold microwire with STI50 solder have been presented when soldering hybrid integrated circuits and microassemblies on printed boards. The dependence of dissolving of gold wire on the temperature and duration of soldering has been established as well as on holding time at a seam temperature of 100 ° C; the interaction of STI50 solder with gold coating on UHF and HIC boards has been considered when soldering on metallic substrates.

The model of iron with Pak-Doyama pair interatomic potential was used as an example to demonstrate by molecular dynamic calculations that the structural stabilization of an amorphous phase of pure metals is due to the formation of a percolation cluster composed of the interpenetrating and mutually contacting icosahedra whose vertices and centers are occupied by atoms.

The structure of the (001) fcc/(001) fcc interphase boundary of a system consisting of a hemispherical Ni (or Cu) crystal nanoparticle and a Pd crystal substrate was studied depending on the nanoparticle rotation angle θ = 15°, 20°, 25°, and 30°. A molecular dynamics simulation including multiparticle potentials calculated in the framework of the embedded atom method was used in this study. It was shown that, under given annealing conditions, the nanoparticle rotation depends on the size; namely, the annealing of small nanoparticles leads to their rotation to the position corresponding to the coincidence orientation at the interphase boundary, while the position of large islands remains practically unchanged. It was established that the atomic rearrangement at the interphase boundary affects only lattices with a larger parameter.

The isochoric heating of amorphous iron at an average rate of about 6.6×1011 K/s was modeled by the molecular dynamics method using the approximation of Pak-Doyama pair potential. The bcc crystallization of the model system was found to occur in the temperature range 1100–1180 K.

Internal friction in metallic materials experiencing a thermoelastic martensite conversion under conditions of a monotonically changing thermodynamic stimulus is determined by two main factors: irreversible processes involving growth of crystals of the new phase, and cyclical motion of the phase boundaries under the action of applied periodic stresses. While the losses caused by irreversible processes decrease with increase in loading amplitude, depending on the type of conversion the amplitude dependence of the background component of internal friction may be of a complex nonmonotonic character, with a maximum in losses at certain oscillation amplitudes. At low amplitudes sections of the boundary unattached to defects perform cyclical motions like membranes, and the losses due to the thermal conversion effect may produce a significant contribution to the overall damping level only at the membrane resonant frequencies. For amplitudes exceeding the critical boundary detachment stress internal friction increases, passes through a maximum, and then decreases anew. The amplitude dependence of internal friction behaves in a similar manner in the process of creation and subsequent collapse of crystals of the new phase in the field of an external periodic load.

The complete set of equations describing the self-consistent dynamics of coherent interphase boundaries and the elastic and temperature field generated by them in a crystal, which undergoes diffusion-free phase martensitic transformation, is obtained in terms of thermodynamics and the classic theory of continuum, with the Lagrangian formalism used.

Techniques have been developed (torsional oscillations, ν ∼ cps; flexural oscillations, ν ∼ kc/s) and measurements of the low-frequency internal friction of strained and annealed metal whiskers and thin films were made in the temperature range from 20 to 1000°C. A dissipation mechanism taking account of aftereffect is suggested and the value of internal friction calculated. The expression obtained for Q −1 is used for determining the length of the dislocation segments which tear away from the pinning points in the process of recovery. The theory suggested is in qualitative agreement with the experiment.