卷 119, 编号 6 (2018)

The processes of direct and two-stage production of photoelectrons and the participation of internal states in the spectra of electrons from valence bands with resonant photoemission in copper chalcogenides Cu(In,Ga)Se₂ have been studied experimentally. Final two-hole states in photoemission have been obtained at the threshold excitation of the Cu 2p level. The strong interaction of holes leads to the multiplet splitting of these states. The value of the Hubbard repulsion of holes on the copper atom has been found to be 7 eV.

Metallic multilayer spin-valve nanostructures that comprise the exchange-coupled ferromagnet/ Ru/ferromagnet structure in the free layer have been synthesized by magnetron sputtering. For microobjects (meanders) formed from CoFe/Cu/CoFe/Ru/CoFe/FeMn/Ta spin valves with different thicknesses of ruthenium and copper layers, the dependences of the magnetoresistive sensitivity and low-field hysteresis loop shift on the meander strip width have been studied. Sensing elements characterized by high magnetoresistive sensitivity have been manufactured.

A bulky copper cylindrical shell with an internal diameter of 118 mm and a wall thickness of 5.9 mm has been exposed to an explosion of a cylindrical explosive charge uniformly distributed around it. A cylinder with a diameter of 57–58 mm has been obtained as a result of high-speed deformation caused by the explosion. A metallographic analysis of the cylinder structure shows that the shell collapses under the influence of axially symmetric radial deformation, which is accomplished by both twinning and sliding mechanisms. It is determined that axial deformation occurs along with the radial deformation. The microstructure of the cross-section consists of three zones. A wide annular deformation zone is formed on the outside, an annular recrystallization zone is formed closer to the center, and a circular region with a dendritic structure is formed at the center. The presence of dendrites indicates that the temperature at the boundary of this region reaches the melting point of copper. The temperature change along the radius of the cylinder has been calculated.

The structure of a hafnium crystal grown by the method of floating zone melting which underwent upon cooling the β → α (bcc → hcp) polymorphic transformation has been studied using the metallography, EBSD analysis, and electron microscopy. It has been shown that the α-phase structure of as-cast hafnium consists of lath-shaped crystals grouped into packets. As a rule, the α-phase grains contain several packets of different orientations from 12 orientations that can arise according to the Burgers orientation relationships. The boundaries of the α-phase grains and packets differ significantly. The grains have smooth boundaries, whereas the boundaries of packets are wavy. The misorientations between separate laths in a packet are less than 1°. Extended twins with a \({\left\{ {10\;\bar 1\;2} \right\}_\alpha }\) twinning plane have been discovered in the structure of hafnium. The presence of twins in the hafnium crystal is due to the influence of the total internal stresses caused by the temperature gradient that arise upon zone melting and by the β → α phase transformation. The fracture of the hafnium crystal at room temperature occurs along the basal (0001) plane. The typical fracture is brittle-viscous with a predominance of the brittle component.

The ab initio computer simulation of lattice parameters and local structure distortions caused by interstitial carbon atoms in the iron-carbon system has been carried out using WIEN2k software. For the calculations, the full-potential method of linearized augmented plane waves (LAPWs) taking into account the generalized gradient approximation of PBE–GGA was used in a supercell of 54 iron atoms with periodic boundary conditions. The carbon dissolution energy has been found to be 0.85 eV for bcc iron, and 0.79 eV for bct iron. The carbon–carbon interaction energies in the ferromagnetic bct iron have been calculated. It has been found that accounting for tetragonal distortions considerably changes the interaction energy of carbon atoms in comparison with that of the bcc iron. Both the maximum degree of tetragonality of iron and the maximum attraction of carbon atoms have been observed for the case of carbon atoms placed in octahedral pores of the same type. If carbon atoms are in different types of octahedral pores, the tetragonal distortion of the lattice is weak. The obtained results are in good agreement with the Zener–Khachaturyan hypothesis and experimental data of Kurdyumov.

The application of the method of molecular dynamics based on the use of pair interatomic potentials has been discussed to study various deformation processes during structural and phase (martensitic) transformations in metallic single and polycrystals. It has been shown that the method of molecular dynamics in a two-dimensional model makes it possible to qualitatively analyze the processes of grain-boundary sliding and other mechanisms of plastic deformation in polycrystals. It is also an efficient tool for describing diffusionless martensitic transformations in metallic materials. As an example, the use of the method for simulating grain-boundary sliding in a polycrystal with nonequilibrium grain boundaries is presented and the mechanisms of overcoming an obstruction in the form of a protruding segment of a grain have been demonstrated at the atomic level. The application of this method for describing the dynamics and morphology of the thermoelastic martensitic transformation has been illustrated by the example of the titanium nickelide and manganese alloys.