• Formation of an ultrafine-grained structure in various metals and alloys during radialshear rolling

    pg(s) 80-82

    The paper briefly discusses the main features of radial-shear rolling and provides an overview of its effect on the formation of an ultrafine-grained structure in various non-ferrous and ferrous metals and alloys. The conducted review showed that radial-shear rolling is the most promising way to form an ultrafine-grained structure in long bars made of both non-ferrous and ferrous metals and alloys, as well as from various composite materials.

  • Iinfluence of titanium boride additives TiB2 on the phase composition, substructure and mechanical properties of powder composite 65% Fe  35% FKh800

    pg(s) 73-79

    X-ray diffraction analysis of the Fe-35%FKh800-(0.38-2.2%)TiB2 system samples showed that a multiphase composition of materials is formed during the sintering process. The basis of the sintered composite is the ferrite α-Fe phase, which is a metallic ironchromium matrix, with γ-Fe, complex iron-chromium carbide (Fe,Cr)7C3, and carboboride phases in small amounts: borocementite – Fe3(B0.7,C0.3) with a rhombohedral lattice and carboboride Fe23(C,B)6 with a cubic lattice and a number of carbides (Cr7C3, Cr3C2). The research established the non-monotonic nature of the effect of the TiB2 additive content on the lattice parameters of the ferrite α-Fe and austenitic γ-Fe phases, as well as on the change in the intensity of the 111 line of the austenitic phase. According to the phase composition data and studies of the fine structure (substructure) of the sintered samples of the Fe-FKh800-TiB2 system materials, it can be noted that the components of the TiB2 alloying additive take an active part in the formation of the phase composition, as well as in the process of alloying the matrix phase, which is reflected in the numerical values of the substructure parameters.

  • Experimental coatings for photovoltaic panels obtained by the sol-gel method based on compositions with the participation of Y2O3 and ZrO2

    pg(s) 33-36

    A summary study of the development of solar energy and the main factors determining the productivity of photovoltaic systems has been carried out. The predominant surface contaminants of solar panels, reducing the efficiency of photovoltaic installations, and the existing different design types of cleaning systems for their effective removal are examined. The main trends in the development of singlelayer and multi-layer hydrophobic and other oxide coatings with diverse performance indicators suitable for solar panels are traced. In laboratory conditions, experimental self-cleaning coatings (based on compositions with the participation of Y2O3 and ZrO2) deposited by the sol-gel method on vitreous samples were obtained. The structure and morphology of the prepared thin films and the technological conditions for the deposition of nanoscale layers with different functional characteristics were investigated. The experimental results represent a prerequisite for the development of a series of additional compositions and a detailed technological regime for obtaining various modifications of resistant, long-lasting self-cleaning coatings, potentially applicable to photovoltaic panels.

  • The influence of aging parameters on thermal, mechanical and structural properties of the EN AW-6060 aluminum alloy

    pg(s) 29-32

    This paper investigates the influence of aging parameters (temperature and time) on thermal, mechanical and structural properties of the EN AW-6060 aluminum alloy. Thermal diffusivity and hardness were measured after applied heat treatments followed by investigation on scanning electron and transmission electron microscopes. Heat treatments included: solutionizing at 550°C for 1 hour followed by quenching in ice water; after quenching samples were aged at two separate temperatures of 180°C and 200°C for 1-8 hours. The results show that hardness gradually increases with aging time achieving peak value of 95 HV10 after aging at 180°C for 5 hours. Thermal
    diffusivity also increases with both aging time and temperature achieving peak values after aging at 200°C for 4 hours. SEM/EDS analysis show the existence of finely distributed precipitates containing Mg, Si and Fe. TEM investigation confirms the existence of rod-shaped precipitates several nanometers in length.

  • Preparation and adsorption properties of mixed zinc-calcium phosphates

    pg(s) 337-338

    Here we present data on the preparation and adsorption properties of mixed zinc-calcium phosphates in aqueous dispersions. The phosphates were prepared by co-precipitation from aqueous solutions followed by autoclaving. The effects of various Ca/Zn initial molar ratios and the type of Ca- and Zn-precursor salts (chlorides and acetates) on the structure, morphology and adsorption properties of the obtained phosphates were investigated. Preliminary data on the adsorption of methylene blue indicated that the as obtained mixed zinccalcium phosphates are promising candidates for application as adsorbents.

  • A study on deflections of GFRP reinforced concrete beams.

    pg(s) 329-333

    Steel reinforcing bars have not performed well in applications where members were subject to corrosive environments. Alkaline concrete protection can provide relatively good protection of the steel reinforcement, but when these are exposed to an aggressive environment or the protection breaks down, the reinforcement starts the corrosive process and it leads to rupture and fragmentation of the protective layer of concrete.
    These reasons lead to high maintenance costs, repairing or even replacing them. This problem prompted a lot of researchers to seek alternative materials with characteristics better than steel to be used in construction. GFRP bars, which are fibers with high resistance immersed in a polymer resin matrix, with a high tensile resistance and also resistant to corrosion, emerged in the 1990s as an alternative to replace steel rods. The use of GFRP is increasingly accepted by the countries, which are trying to create or adopt special codes for their use in building structures.
    This paper will take a quick look over GFRP materials and their mechanical properties, but also will aim to provide some ideas on the study of concrete members reinforced with GFRP bars and their design based on SLS method as it rapresents the most problematic one, focusing on deflections of GFRP reinforced beams.

  • Structure and physical-mechanical properties of bulk and ribbon amorphous and nanocrystalline iron-based alloys

    pg(s) 288-293

    The physic-technological basis for fabrication of bulk rods and plates of amorphous, amorphous-nanocrystalline and 100% nanocrystalline alloys at melt cooling rates from 80 to 3200 K/s with crystal sizes from 10 to 50 nm has been developed. The multiphase structure formed in the initial bulk samples, as well as in the process of nanocrystallization of amorphous ribbons, is characterized by record microhardness values of 17-22 GPa. Amorphous powders (20-100 μm) of Fe55Ni8Co6Mo4Cr2V1Al2P9C6B5Si2 and Fe61.37Co6.84Cr3.78V0.85W0.82Mo1.06Nb0.85B19.87C1.99Si2.57 alloys are used to create a wear-resistant coating on structural stainless steels and low-carbon St3 by the gas-thermal “cold” method » sputtering and subsequent melting of the applied layer.The values of microhardness (Hμ) of nano-coatings significantly exceed the microhardness of all known tool steels. Examples of technology transfer and practical using of developed amorphous and nanocrystalline alloys are presented.

  • Development of a composite alloy zinc-containing material and investigation of its influence on the chemical composition of BRSN5ZN5PB5 powders produced by the method of induction melting and spraying the melt with an inert gas

    pg(s) 285-287

    The process of obtaining bronze powders of grade BrSn5Zn5Pb5, obtained by the method of induction melting and spraying of the metal melt with an inert gas, has been studied. It is known that in the production of BrSn5Tsn5Pb5 powder, the main losses of zinc occur during the melting of the components. To study the possibility of reducing zinc losses in the melt, a zinc-containing composite alloying material has been developed. Its effect on the chemical composition of BrSn5Zn5Pb5 powders obtained by induction melting and spraying the melt with an inert gas has been studied.

  • Production method role for the composite powders quality

    pg(s) 282-284

    Self-propagating high-temperature synthesis (SHS), refers to a technology for the production of useful materials (mainly composite powders) that uses combustion processes. The solid combustion process results in the release of more heat which is needed to rebond the elements of the system and it is this extra amount of heat that is used to self-sustain the combustion process and its development. This process is known as self-propagating high temperature synthesis.
    This paper presents the study of the magnetic properties of the products obtained by this method in comparison with other methods which use nickel-zinc ferrites. The latter are widely used in radio devices, antennas and transformer cores, as well as in high-frequency filters where the current loss is significant.

  • Structure, phase composition and tribological properties of iron-based composites in situ synthesized from powdered Fe-high-carbon ferrochrome mixtures

    pg(s) 278-281

    The article presents the results of investigations of tribotechnical properties of powder composite materials based on the ironhigh-carbon (ФХ800) ferrochrome system during dry friction with ШХ15 steel at various loads of 30, 60, and 100 N. It was found that an increase of the load from 30 to 100 N leads to an increase in the coefficient of friction from 0,45 to 0,5 (for 25% ФХ800) and from 0,40 to 0,46 (for 40% ФХ800). At the same time, the mass wear of samples made of powder materials decreases with an increase in ФХ800 content from 25 to 40 (wt. %) and with growth of the load from 30 to 100 N, respectively, from 3,5 – 8,0 to 0,75 – 1,6 mg/km., which provides wear resistance improvement (km/mm) by 2,8 – 2,2 times. X-ray phase full profile analysis using the Rietveld method established that there are 2 phases: metallic α-Fe (79,68%) and carbide Me7C3 (20,32%) in the composite Fe – 25%ФХ800 and 3 phases: α-Fe (69,5%), γ-Fe (3,96%) and carbide Me7C3 (26,57%) in the Fe – 40% ФХ800 composite. Topographic studies of 2D profiles of worn surfaces of composites after friction under different loads were conducted. The results of optical profilometry show that the main mechanism of destruction of the powder composite surface during dry friction with ШХ15 steel is adhesive wear (seizing) of the contacting surfaces.

  • The study of the corrosion zinc-nickel coated ST2 stainless steel

    pg(s) 275-277

    In the present work, the corrosion of Zn-Ni coated steel in the presence of acetic acid was studied. Corrosion tests were carried out in salt spray and the corrosion rate was determined by the weight loss method. The results showed that the Zn-Ni layer acted as sacrificial coatings on steel, the acetic acid, even if it is a weak acid. Also, in this paper, a simulation was carried out regarding the corrosion protection of steel attacked by acetic acid using a sacrificial anode (Zn alloy). The results obtained from the simulation agree with the experimental ones.