Vol 10, No 1 (2019)

The article describes a new algorithm for predicting the structure of a reinforcing phase at heat treatment of high carbon steels. This approach is based on the construction of the distribution function of grains in their size for a set of regions in which the temperature gradient is sufficiently small. The proposed algorithm makes it possible to avoid calculating formation and growth of a single embryo and to proceed to modeling the structure in a relatively large cell, which can significantly reduce computational costs. To solve the problem of determining the distribution function of temperature fields, it is proposed to use a new approach based on integral heat transfer equations; this allows, on one hand, estimating the accuracy of calculations by the mismatch vector and, on the other hand, averaging thermophysical characteristics in a natural way and solving the problem on large-scale grid splits. Owing to the nonlinearity of the task and the need to use iterative procedures, integral equations provide the necessary conditions for their convergence. As a result of creating specialized software and carrying out a series of numerical calculations, it is possible to theoretically determine the necessary conditions for heat treatment for products made from steel of a particular grade: size and power of the heating inductor, the speed of its movement, the type of coolant and its feed rate, the depth of the hardened layer, etc.; as a result, this will make it possible to determine in advance the structure of the heat-treatable layer and reduce the total costs of experimental work.

Development of the concepts for the mechanisms of brittle fracture of metals and alloys in aggressive hydrogenous media is examined.

One of the simplest and most promising ways of obtaining materials with specified properties based on ceria, which is sol-gel synthesis through intermediate β-diketonate complexes, is considered. Apparently, this method is less energy and resource consuming, as well as more environmentally friendly compared to other approaches. The implementation techniques are shown and the regularities of the formation of ceria nanoparticles during sol-gel synthesis are described.

The effect of thermal treatment in air and SZhR-3 on BNKS-18 nitrile-butadiene rubber is studied in this work. A stretching device compatible with an atomic force microscope is developed to study the thermal effects on a change in surface structure of BNKS-18 during deformation. There are structural rearrangements in the surface during deformation and a change in the Poisson ratio and surface roughness of BNKS-18 before and after thermal treatment.

The TEM method was used to study dislocation substructures and their change at developed plastic deformation of fcc alloys upon departure from the site of destruction. Polycrystalline Cu–Mn alloys with grain sizes of 10, 100, and 240 μm were the materials of study. The parameters characterizing dislocation substructures were measured, and the patterns of their change depending on the distance from the site of destruction were determined. The influence of grain size on the change in these patterns is revealed. It is established that, near the site of destruction of samples, the highest density of disordered boundaries and curvature–torsion of the crystal lattice are observed.

The mechanical characteristics are studied for macroporous composite implants on the basis of β‑Ca/PO₄)₂/polylactide and β-Ca/PO₄)₂/polycaprolactone obtained by means of thermal-extrusion 3D printing. The effect of the degree of filling exerted on the strength, Young’s modulus, and the characteristics of the material destruction is described for the polymer, as well as for the three-dimensional structure filled with phosphate cement.

The influence of titanium dioxide powders obtained from the waste sorbent produced when discharges with nonferrous heavy metals are purified on the main technical properties and processes of structure formation of Portland cement stone was studied. It is shown that titanium dioxide modified with nanodispersed powder added to the cement composition plays the role of a modifier accelerating processes of hydration and hardening of cement. In the presence of titanium dioxide, the cement stone acquires the capability of self-purification owing to photocatalytic activity of the introduced additive.

The effect of low-cycle fatigue loading on interlayer strength and fracture toughness of discretely reinforced carbon-carbon composite material (CCCM) for friction use is studied. The material demonstrates good resistance to fatigue loads. In the described mechanisms for increasing CCCM fracture toughness after applying fatigue load, the fiber–matrix interface plays a key part. The dependences of CCCM fracture toughness and interlayer strength on the fatigue loading parameters are determined.

There is a growing interest in bioactive materials of medicinal use, because their employment gives large opportunities in the recovery of the integrity of bone tissue, which is dictated by their biocompatibility and bioactivity. The authors have compared cytocompatibility and matrix properties of a series of nanostructured calcium phosphate cements and have elaborated recommendations on improvement of primary in vitro screening of the materials dedicated for the replacement of osteochondral defects.

The structural features of Cu–Ag alloys mechanically synthesized by means of severe plastic deformation at a room and cryogenic temperature are revealed using X-ray diffractometry and electron microscopy and via in situ measurement of structure-sensitive characteristics such as shear stress depending on the deformation level. The effect of cryogenic strain temperature consists in a special character of change in the structure and shear stress of the formed alloys, which, in turn, affects the composition of the solid solution and the kinetics of structural transformations, as well as the mechanical properties.