Materials Science. Non-Equilibrium Phase Transformations.
Vol. 9 (2023), Issue 1

Table of Contents

  • Modeling of the structural evolution of carbon steel hypereutectoid structure subjected to reforging under pulsating contact stress loading

    pg(s) 3-6

    The paper presents the results of microstructural studies of 16MnCrS5 steel hypereutectoid structure subjected to reforging under pulsating contact stress loading. It is revealed that the local evolution of the structure in the focus of contact loading has signs of selfimprovement with the transformation of the isotropic morphology of the carbide phase into an anisotropic one with signs of textural riveting. Instead of the initial structure with a uniform carbide phase distribution, signs of textural anisotropy with reinforcement elements of the modified layer high-carbon hypereutectoid zone with carbide inclusions are formed.

  • The Effect of Alumina Particles Reinforcement on the Mechanical Properties of Base Alloy Melt of (6061)

    pg(s) 7-12

    This paper aims to study the reinforcement effects of alumina (23) particles on the mechanical properties of base alloy melt of (6061). The samples of metallic composites with dispersed particles percentage (5%, 10% and 15%) are prepared by casting vortex method, which help the particles entrance in the matrix and distribution of it in homogeneous form. The purpose of this study is to improve the hardness, impact strength, tensile strength, and compressive strength, which are increased with the increment of the added particle’s amount due to the hardness of alumina particles. Based on the results it concluded that the value of the durability increases with the increase in the percentages of the particles by weight between three stages. Also, the addition of aluminum oxide particles increased the tensile resistance and thus improved the mechanical properties of the base material. It was also noted that with the addition of aluminum oxide, the melting point of the metal increased and reached about 980 degrees Celsius.

  • Effect of electrode polarity on the properties and wear resistance of 3D titanium alloys under reaction electro-spark treatment with WC and TIB2 – based composition hard alloys

    pg(s) 13-18

    This work discusses the properties of 3D titanium alloys with wear-resistant coatings of hard alloy electrodes based on WC-TiB2-B4C and solder mass of Co-Ni-Cr-B-Fe-Si-C, produced by reaction electrospark processing (RESP) at positive and negative polarity. Through profilometric, metallographic, XRD, SEM, EDS and tribological methods, the complex influence of polarity and pulse energy on the topography, composition, properties, and wear characteristics of the coated surfaces was investigated. The differences in the coatings obtained with the two polarities were identified. Coatings with similar roughness and thickness were obtained, which can be changed by changing the modes for RESP within the limits Ra =2.5÷5μm, δ= 8÷40μm, with microhardness 8 to 14 GPa and 2-4 times higher wear resistance than that of the substrate. At RESP with negative polarity and pulse energy up to 0.04 J, the coatings have comparable characteristics and properties to those at positive polarity, but lower roughness, finer structure and lower coefficient of friction. These coatings can be successfully used to reduce roughness and surface defects and improve the wear resistance of 3D titanium alloys. The pulse energy and polarity of RESР, producing coatings with minimum roughness and maximum wear resistance, have been determined.

  • Studying the composition and properties of white eco-cement

    pg(s) 19-22

    The possibility to produce white Eco-cement with the use of a dry method under low-temperature firing of a raw material mixture based on the CaO – SiO2 – Al2O3 – MgO system is shown. Computer calculations were performed and an analysis of the dependence of the characteristics of cement clinker on the quantitative ratio of raw components was carried out. A new composition of the raw material mixture with a decrease of 19 wt. % amount of the carbonate component and, accordingly, CO2 emissions during combustion was determined. The peculiarities of phase transformations in the material during firing with a maximum temperature of 1100 ᵒС when microtalcum was introduced into the initial mixture with the formation of pericloze, ockermanite and merwinite as a factor in the structure and properties of cement clinker were noted.

  • Microhardness dependence of Ti-Zr alloys on time and temperature of sintering

    pg(s) 26-29

    Commonly used metallic biomaterials are titanium and its alloys, cobalt-based alloys and 316L stainless steel. Titanium alloys are reference materials in biomedical applications due to their desirable properties such as excellent mechanical properties and good biocompatibility. Since presence of different metals can significantly alter the properties of titanium it is usually alloyed with other metals, including the zirconium. In this work Ti-20Zr was prepared by powder metallurgy by mixing the powders in a ball mill and sintering in a tube furnace under argon atmosphere. Microscopic analysis with the light microscope showed that the porosity decreased with increasing temperature and sintering time. Scanning electron microanalysis with energy-dispersive spectrometry showed the two-phase microstructure of the sintered alloy. Microhardness was determined by Vickers method. A longer sintering time and a higher sintering temperature resulted in higher microhardness values.

  • CeО2-ZrО2 Multi-layer Cubic Coatings Obtained by Sol-Gel Technology

    pg(s) 30-31

    A solution was synthesized in a system ZrO2-CeO2 by sol-gel synthesis and deposited by the immersion method. The pretreated Nb substrate was treated with sulfuric acid and absolute alcohol solutions. Layering was in three stages. The sample was heat treated at 500°C. The obtained results are characterized by XRD, XPS, CEM analyzes.

  • Tribological properties of PVD nanocoatings

    pg(s) 32-34

    The paper presents the results of research aimed at determining selected tribological properties of PVD nanocoatings. PVD nanocoating of the 4th generation duplex nACRo4 was applied to the surface of shaped parts of molds and cores for high-pressure aluminium casting. The surfaces were laser textured with a random texture. The tribological properties of the coating were determined by measuring the friction coefficient using the Pin on Disc method at a temperature of 300 °C. Confocal microscopy was used to determine the parameters of the microgeometry of surfaces with random texture topography. The aim of this surface treatment was to analyse the adhesion effect of commercially used ones of lubricants in the technology of treatment of shaped parts of molds when casting aluminium alloys under high pressure on machines with a cold filling chamber. By checking the integrity of textured surfaces with deposited with the duplex PVD coating of the 4th generation nACRo4, no damage to the integrity of the deposited material was detected PVD coating. Elements forming the PVD coating were detected on the surface by semiquantitative EDX microanalysis.