Volume 7, Issue 4, December 2017

Simple approximate expression for the displacement field in harmonic triangular lattice under imposed volumetric mean strain is derived.

A superconducting multifilament wire made of Nb-Ti alloy was investigated by methods of atom probe/field ion microscopy, three-dimensional atom probe, high resolution electron microscopy (HREM) and computer simulation. Figure shows a HREM micrograph of the coherent interphase boundary with an ideal conjugation of atomic planes of adjacent grains.

The new type of core-shell structures of antimony ranging from 10-4 to 10-6 m, obtained in a single-stage process as a result of spontaneous crystallization of the melt at average cooling rates of the melt are 1 – 100 K/second. The structures consist of different forms of the same substance, whereas the core is represented by the mono-crystalline gray antimony and the shell is a deformed two-dimensional film.

Poisson’s ratio dependence on longitudinal deformations for four two-dimensional auxetic cellular samples.

Scanning electron microscopy was used to study the behavior during annealing of iron, in which an ultrafine structure of two different types was created by deformation under high pressure: cellular and submicrocrystalline. The figure shows orientational maps (EBSD) of iron with different initial type of structure after annealing at 750 ° C, 1h.

Twin-oriented bands up to 20 m in width appear near grain boundaries of coarse-grained aluminum during single pass of dynamic channel angular pressing. Analysis of their deviations from the ideal twin misorientation showed that they could be formed both at an early and at a later stage of deformation.

In this paper, we study some low-dimensional bushes of nonlinear normal modes in graphene using ab initio calculations based on the density functional theory. The amplitude-frequency dependencies of one-dimensional bushes are found. The excitation transfer between nonlinear vibrational modes of different symmetry that belong to the same bush is investigated.

The movement of oxygen ions in the Al melts under action of a constant electric field is studied by molecular dynamics. The speed and intensity of oxygen ions movement across the melts depends on their concentration.

Scheme of the reactor: 1 – the discharge area; 2 – upper tubular electrode; 3 – lower tubular electrode; 4 – the reactor vessel; 5 – solenoid (the inductor); 6 – pulse electrodes, arrows indicate the direction of water flow

Geometry of the surface-stabilized FLC cell.

The dynamics of the system of finite size particles with the rotating central particle calculated on the basis of different models.

The electric properties of Bi5Nb3O15 bismuth niobate polycrystalline samples and chromium-containing solid solutions Bi5Nb3-3хCr3хO15-δ (х≤0.08) were studied using impedance spectroscopy.On the grounds of the performed researches the conclusion about the electron-ionic character of conductivity of solid solutions Bi5Nb3-3хCr3хO15-δ was made.

Bulk ceramic materials based on B4C–ZrB2 systems have been produced by means of pressure-assisted self-propagating high temperature synthesis (SHS) using a mixture of elementary powders B, C and Zr. The influence of reaction mixture composition on microstructure formation and physical and mechanical characteristics of SHS composites have been studied by X-ray diffraction and microstructural analysis.

The study of the iron-containing Bi5Nb3O15 solid solutions has shown that, in the solid solutions iron (III) atoms aggregate with antiferromagnetic and ferromagnetic types of exchange.

Solving of vital problems in development of modern aerospace equipment, power engineering, creation of ion-plasma technologies for processing new products and materials, the development of nuclear power reactors of the fourth generation requires to manufacture structural elements made of materials able to be operated in the temperature range from 1600 to 2200 K. The paper proposes a model for predicting the mechanical properties of high-temperature ceramic composites and extend the understanding the mechanisms of fracture at high temperatures in conditions of intensive dynamic effects.

According to molecular dynamics simulations the silicon alloying the tetrahegonal distortion of steel martensite.

Growth of seeds grains in superconducting ceramics Y123. The seed grown zone contains high density of low-angle boundaries and captured pores.

The influence of the microstructure, its heterogeneity, grain size and distribution of secondary phases on the corrosion rate is demonstrated. The microstructure refinement by the severe plastic deformation leading to the increasing fraction of grain boundaries, promotes the formation of a reasonably uniform protective layer, reduces the inhomogeneity of the second phases and increases the overall corrosion resistance of the ZK60 alloy.

Grain boundary (GB) segregation of Co has the positive effect on both plasticity and strength of nanocrystalline (NC) Al, while Ti atoms in GBs improve only its ductility. Cracking of NC Al and its alloys with GB segregation of Fe or Mg occurs through the formation of nano-voids at GBs followed by their coalescence at higher stresses.

The values of binding energies of carbon nanostructures with the nonconventional geometry of framework calculated using the density functional theory can substantially differ from each other depending on the chosen DFT-functional.

Many questions remain open in the understanding the role of microstructural factors in the acoustic emission (AE) phenomenon occurring in deforming materials. A comparative analysis of AE time parameters in tensile testing of pure aluminum, copper, silver and nickel specimens having very different values of stacking fault energy (SFE) was undertaken in the present work to clarify the SFE effect on the AE signal. Continuous digital wideband recording was used for AE waveform registration, which offers the possibility to avoid the threshold discriminators and to analyze a continuous AE signal generated during plastic deformation mediated by dislocation mechanisms. The power of the AE signal were selected as the descriptive parameters. Following the evolution of dislocation structures, the AE energy parameters were demonstrated to have a similar behavior in all investigated materials, i.e. the AE level increases sharply at the onset of plastic flow and then decays gradually during the uniform strain hardening stage. However, the absolute values of the AE amplitude and energy differ significantly depending on SFE. It was shown unambiguously that in contrast to expectations, the AE energy parameters reduce as the SFE value increases. This effect is discussed qualitatively in terms of the features of dislocation behavior, which are governed by the SFE value.

Martensitic transformation is investigated in two-dimensional molecular dynamics model. Dislocations affect the direct martensitic transformation as the nucleation centers.

Effects of severe plastic deformation by isothermal сryorolling at a temperature of liquid nitrogen with a strain of e~2 and subsequent natural and artificial aging on the evolution of structure, hardness and resistance to intergranular corrosion (IGC) of the preliminary quenched D16 aluminum alloys of conventional and Zr modified compositions, were investigated. It was concluded that the main factors, determining the alloy microstructure changes, mechanical and corrosion behavior, are the volume fraction and morphology, and spatial distribution of second phases - excess phases and precipitates.

The set of points of strength surface in the space of principal stresses is determined for 2D case. The approximation of this set of points permits one to obtain the strength criterion in the analytical form.

A model for elastic bonds in solids, composed of bonded particles is presented. The model may serve for description of elastic deformation of rocks, ceramics, concrete, nanocomposites, aerogels and other materials with structural elements interacting via forces and torques.

Typical TEM structures of pre-quenched 1420-type alloys after HPT (RT, 4 revolutions, P=6GPa) and further annealing

Shock-wave loading of reactive materials by throwing a flyer

Combined SPD method including multiple abc-pressing and multi-pass rolling resulted in the formation of two-phase ultrafine-grained binary Zr-1Nb alloy structure, where the average alloy structural elements size was 0.22 µm. Ultrafine-grained alloy included high level of mechanical properties (yield strength – 450 MPa, ultimate tensile strength – 780 MPa, microhardness – 2800 MPa) at low elastic modulus (51 GPa).