Том 120, № 1 (2019)

The spectrum of the electron paramagnetic resonance of the Er³⁺ ion in the matrix of metallic copper has been studied at 9.8 GHz in the temperature range from 1.7 to 4.2 K. The spectrum corresponds to the crystal field of cubic symmetry at g = 6.805 ± 0.01; this value agrees with the expected value for the doublet Γ₇. The residual width of the EPR line (T = 0 K) for the even isotopes of erbium was only 4.5 Oe. The temperature and concentration changes in the width of the line indicate the existence of an RKKY interaction between erbium ions. The hyperfine structure (HFS) of the EPR line for the ¹⁶⁷Er isotope has been identified. The positions of separate HFS lines are described with an accuracy of 1.5 Oe by a constant A = 74.25 ± 0.1 Oe. The increase in the accuracy of the determination of the hyperfine splitting of lines of the Er³⁺ ions made it possible to reveal a weak exchange narrowing of the HFS upon an increase of the erbium concentration in these alloys.

This study presents the results of an examination of the mechanical properties and structure of wear-resistant composite Ti–TiC-based coatings, which were formed on commercially pure titanium by electric-arc processing in an aqueous electrolyte, with transition and valve metals (Al, Ni, Cr, and Si) introduced into their composition. This study demonstrated that the change in mechanical properties can be attributed to the formation of the martensitic phase at the titanium–TiC interface, which is induced by hardening phenomena associated with electric-arc processing.

This study presents a wide spectrum of experimental investigations of alkali borohydrides МВН₄ (М = Li, Na, K, Rb, Cs) and complex hydrides with substituted anions Li(BH₄)_{1– y}I_y, LiLa(BH₄)₃Cl, and Na₂(BH₄)(NH₂) obtained by the nuclear magnetic resonance method, quasielastic neutron scattering spectroscopy, and X-ray diffraction analysis. Activation energies for reorientational motion of anions in alkali borohydrides have been systematized, and possible configurations and types of jumps of ВН₄ groups have been discussed. It has been shown that the activation energy of reorientations of ВН₄ groups change nonmonotonously with the growth of the cation radius. Substitution of halides and amides for anions in complex hydrides leads to an enhancement in the frequency of anion reorientations at low temperatures, a change in the translational diffusion of cations at the expense of a change in the crystalline structure, the appearance of vacancies in the lattice, and influence of the paddle-wheel effect. Interrelation between the type of anion reorientations, cation diffusion, and the crystal lattice has been demonstrated.

This paper investigates the microstructure and superplastic indicators of industrial titanium sheets (Ti–4% Al–1% V–3% Mo alloy) in a temperature range of 750–900°C and strain-rate range of 1 × 10^–5 to 1 × 10^–2 s^–1. The results show that the deformation temperature of 875°C and strain rates 6 × 10^–4 to 2 × 10^–4 s^–1 provide a relative elongation above 700% and a strain-rate sensitivity index m > 0.4. Under these deformation conditions, at the initial stage there is a decrease in the grain size of the α and β phases by 1.5–2 times, and a strong softening in the stress–strain curves can be observed. The dynamic recrystallization explains these effects. As the degree of deformation increases to above 50%, a steady-flow stage and a weak growth of the α-phase grains are observed; the grain size of the β phase remains unchanged. The calculated values of the effective activation energy Q were 194–237 kJ/mol, which suggests that the superplastic flow under the investigated temperature-rate deformation conditions is controlled by the grain-boundary diffusion.

An a luminum matrix composite reinforced with 1–5 wt % graphite nano platelets ( CNPLs ) has been fabricated by cold pressing followed by hot extrusion techniques. The wear test conditions used were implemented at different wear loads, (10 N, 20 N, 30 N, 40 N, and 50N) with three different sliding speed of 0.2, 0.4, and 0.8 m/sec. The effects of nano graphite content on the structure characteristics and properties of composites were investigated. Scanning electron microscopy (SEM) has been used to examine the dispersion of CNPLs and aluminum. The results showed that CNPLs were distributed homogeneously in the (CNPLs/Al) composites. The CNPLs content significantly affects the mechanical properties of (CNPLs/Al) composites. Meanwhile, the 2.0 wt % CNPLs /Al composite is found to exhibit the highest hardness. Experimental results showed that at all the loads studied the wear resistance of the composites was better when compared with the monolithic aluminum matrix.

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.