Materials Science. Non-Equilibrium Phase Transformations.
Vol. 4 (2018), Issue 3

Table of Contents

  • Development of technology for manufacturing products with high mechanical strength based on aluminum oxide

    pg(s) 73-75

    The results of development of the technology for manufacturing samples of insulators made of alumina ceramic with an aluminum oxide content of up to 95% are presented. The maximum tensile strength of the produced insulators has been investigated. The structures of the chip of the ceramic insulator surface have been obtained. It is shown that a change in the aluminum oxide content by 8-10% leads to an increase in the strength properties of the product by 1.5 times. The developed technology can be used to produce high-strength dielectric products, for example, antenna rod insulators, applied in the field of electrical engineering, radio engineering and other industries.

  • Elastic properties of Fe under high pressures

    pg(s) 76-78

    The definition of the n -order ( n>=2) elastic constants of a loaded crystal and the calculation method of the second and third order elastic constants of hcp crystal under hydrostatic pressure from the energy-deformation relation are given. The energy at the various pressures and deformations of hcp iron is obtained in framework of DFT. The calculations of the second and third order elastic constants of hcp Fe at 20-340 GPa (T=0K) are performed. The Gruneisen parameters for long wave acoustic modes in hcp iron are defined. The obtained results are used for the stability analyses of the hcp phase of iron at high pressures.

  • Influence of the external magnetic field on the structure and properties of the hypereutectic aluminum-silicon alloy

    pg(s) 79-82

    The effect of a constant magnetic field during the crystallization of a hypereutectic aluminum alloy on its structure in the solid state investigated. It is shown that the superposition of the magnetic field positively affects the structure of the alloy. A uniform distribution of the doped phases and eutectic in the volume of the alloy is observed. The phase of primary silicon significantly changes the size and the shape. It is established that the influence of an external magnetic field reduces the dimensions of the shrinkage defects. In general, the effect of an external magnetic field on the structure of the alloy leads to an improvement in the operational properties. The obtained measurement results showed more stable hardness values over the cross section of the sample in comparison with the alloy that was not processed.

  • Covalence of the Fe-C interatomic bond and the hardness of martensite of carbon and alloyed steels

    pg(s) 83-85

    A technique for determining the generalized degree of covalence of the interatomic Fe – C bond is proposed by the addition rule taking into account the fractions of Fe2C, Fe4C and Fe6C clusters and cementite in steel. The correlation dependence of the generalized degree of covalence of the interatomic Fe – C bond with the hardness of microstructures observed in eutectoid carbon steel, as well as the hardness of ferrite and cementite, is revealed. A functional relationship between the generalized degree of covalence of the Fe-C interatomic bond and the martensite hardness at different mass content of carbon is established, which ensures the correspondence of the
    calculated and experimental data.

  • Swelling, mechanical and thermal properties of microwave – synthesized intelligent soft materials

    pg(s) 86-88

    Advances in technology since the second half of the 20th century are followed as well as induced by the development of intelligent materials. These materials are able to respond to external stimuli by measurable changes in structure and intrinsic properties. Stimuli-responsive hydrogels are soft smart materials as they exhibit significant changes in physicochemical properties in response to small external stimuli. Acrylate hydrogels are widely used in applications where their smart and soft nature comes to the fore. Synthesis of those materials by conventional heating is time-consuming and unsuitable from the point of energy and sources saving. Microwave-assisted synthesis is promising method that provides polymerization under the more favourable conditions, reducing the reaction time. The focus of present work was to investigate the swelling behaviour, mechanical and thermal properties of acrylate hydrogels synthesized by microwave heating.

  • Model description of grain boundary diffusion processes in microcrystalline solid systems

    pg(s) 89-91

    The simple model of grain and phase boundaries diffusion into polycrystalline solid system with micro grain dimensions is proposed. There are considered different types of diffusion regimes which are realized by definite correlations between volume and grain boundary diffusion lengths and average grain sizes.

  • Dependences of phase transitions temperatures of perovskites ABX3 (X=O or F) upon the interatomic A-X bond strains

    pg(s) 92-95

    The ferro-, antiferroelectric and rotational phase transitions of known binary perovskite structure oxides (ABO3) and fluorites (ABF3) have been considered. Some correlations between their phase transition temperature values, on the one hand, and the interatomic bond А-X (X–O or F) strain values, on the other hand, have been constructed. It has been established that the known perovskite structure binary oxides and fluorites with different phase transition nature, caused of a lot of their composition and structure factors, are conditioned, among another, by the interatomic bond А-X strains in their structure.

  • Experimental data and simulation by the finite element method of the cylindrical steel shaft quenching in water

    pg(s) 96-98

    In the present work, the process of water quenching of a steel cylindrical body imitating a stepped shaft is considered. The cooling function was determined experimentally, based on which the heat transfer coefficient was determined according to an existing methodology. The results obtained are used as input data for simulation using the finite element method. Results are obtained for the cooling functions at different points in two sections of the shaft. The results of the simulation are compared with the CCT curves and with the measured hardness at these points.

  • Electron-beam remelting of Ni-Cr-Al-Y alloys for manufacturing of cathodes for ion-plasma coating

    pg(s) 99-101

    An experimental electron-beam technology for obtaining tube billets from NiCrAlY alloys used as cathodes for the deposition of heat-resistant coatings by the ion-plasma method has been developed. It is established that coatings applied to gas turbine blades of aircraft engines using cathodes of electron beam melting meet the requirements of Motor-Sich JSC TU for this type of products.

  • Effect of thermal-cyclic deformation and heat treatment on the structure and electrical properties of Ст3

    pg(s) 102-104

    The results of the effect of preliminary thermal-cyclic deformation on the microstructure of hot-rolled low-carbon steel Ст3пс are presented. It is shown that the regime of thermal-cyclic rolling leads to a decrease in the average grain size of ferrite from 8 to 6 microns in comparison with the structure of steel after industrial production. There is a decrease in the size of pearlite colonies and their volume fraction in the structure of steel after using thermal-cyclic deformation. The results of the effect of heat treatment: normalization and tempering on the electrical resistivity of the hot-rolled carbon steel sheet Ст3пс produced using thermal-cyclic mode of deformation processing (DTCT). DTCT preliminary thermal-cyclic was rolled (5 cycles at a reduction of 10-15 % in each cycle and cooled to a temperature below the Ar1). And normalizing annealing was carried out in the range from 100 to 900 °C increments to 100 °C for 1 hour. The possibility to reduce the magnitude of the specific electrical resistance of the hot-rolled steel manufactured using DTCT mode through the use of subsequent normalizing at 700 °C on average 10 %, and by annealing – no more than 5 %. A further increase in the time of normalization at 700 °C to 3, 5 and 10 hours has no significant effect on the value of the electrical resistance of the steel subjected DTCT. However, the downward trend in resistivity is maintained. Overall reduction of electrical resistivity of the hot-rolled steel Ст3пс by using
    mode DTCT and subsequent normalizing at 700 °C for 1 hour is more than 12 %.