International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Existing experimental researches show that in order to prevent the destruction of optical elements of modern opto-electronic devices (discs as the light filter linings for IR devices, the input protective windows of laser sighting systems for observation in IR areas of the spectrum, semispherical fairings of IR devices for homing and observation of objects, lightguides for laser medical devices, etc.), electron beam method becomes promising, as it provides cleaning of surfaces, increases their microhardness, makes them more resistant to external influences. The results of experimental studies to improve the properties of the surface layers of elements from optical ceramics after their processing with a moving electron beam with a heat density Fn = 106…1.6∙107 W/m2 and moving speed V = 10-3…10-1 m/s (increase in the surface microhardness from 1.2 … 2.9 GPa (raw elements) to 5.7 … 6.4 GPa (processed elements), the occurrence of hardened layers with a thickness of 210… 230 microns). It has been established that the improvement of these properties leads to an increase in the resistance of elements to external thermal effects: an increase of 1.3…1.7 times the critical values of external heat flows and their exposure times, exceeding which leads to the destruction of elements and the failure of devices for the studied range of change of external pressure is 105…107 Pa; increasing the maximum allowable values of thermoelastic stresses in elements from 50…140 MPa to 160…370 MPa at heating temperatures of 300…1200 K.

The paper presents results of research aimed at comparing selected properties of two types of pipe steels, conventional 17G1S-U steel and alternative S960QL steel. The steels were compared in terms of their chemical composition, microstructure, hardness and corrosion resistance. Static electrochemical corrosion tests were performed on the materials, namely electrochemical impedance spectroscopy (PEIS) and linear polarization (LP) in two electrolytes. The results show different chemical composition and microstructure of materials. 17G1S-U steel has a row-like ferritic-pearlitic structure with a hardness of 200 HV 0.1. S960QL steel has a martensitic structure with a hardness of 353 HV 0.1. Steels showed very close corrosion rate in both electrolytes.

The microscopic and macroscopic views of copper electrodeposits obtained on plastically deformed copper substrates of different deformation degrees have been investigated. Experiments have been performed under galvanostatic conditions. There appear, depending upon the degree of reduction realized during substrate rolling, three types of deposit: epitaxial, homogenous and texture. Epitaxial growth is observed on unreformed substrate and on the substrates with lesser deformation degree (up to 60 %). With the increase of the substrate reduction degree, heterogeneous type of the deposit appeared and the phenomenon of twinning was stated. On very much deformed substrates, as well as in presence of organic additives, field oriented texture type of the deposit is obtained. On very deformed substrates macroscopic uneven deposits appeared, with the linear structure which follows the direction of substrate rolling. Possible explanations of this phenomenon are given.

This article describes the technology of the combined process “equal-channel angular pressing-drawing”. The analysis of the influence of this process on the structure and mechanical properties of aluminum, copper and steel wires is given. The results of the study showed that the proposed combined deformation method “equal-channel angular pressing-drawing” has a significant advantage over the existing technology for the production of high-strength wire. This deformation method due to the combination of two deformations: severe plastic deformation in a matrix with parallel channels and the process of deformation through a drawing die, allows to get a wire with an ultra-fine structure and a high level of mechanical properties, the required size and shape of the cross section in a small number of deformation cycles.

Powder high-entropy alloys (HEA) of TiCrFeNiC equioatomic composition were synthesized by hot forging (HF). The phase composition and parameters of the fine structure of the alloys are determined. It is shown that at all annealing temperatures of the alloys their phase composition does not change significantly and consists of two solid solutions of substitution – FCC and BCC and two carbide phases – TiC and Cr3C2. The mechanical properties of the alloys are at a rather high level – so the maximum strength of the alloy was 2243 MPa and the hardness is more than 62 HRC, which can be explained by the effect of high entropy and in situ synthesis of carbides in the manufacture of alloys.

The high specific strength of Ti-based alloys and composites makes them highly requested materials in various structural applications. However, reinforcement of the alloys with hard particles generally lowers the values of toughness and plasticity of material. A satisfactory combination of plastic and strength can be achieved by formation of layered structures comprising of two and more layers of different materials with different chemical compositions within individual layers. The multi-layer materials allow controlling the mechanical properties of the individual layers by changing microstructure and chemical composition within each layer specifically. In the present study, a cost-efficient process of fabrication of Ti-based multi-layer composites using blended elemental powder metallurgy (BEPM) and TiH2 powder is proposed. Two and three-layered composites based on titanium or Ti-6Al-4V alloy and their metal-matrix composites (MMC) with TiC and TiB were fabricated. Multi-layered samples reinforced by TiC were successfully sintered due to very close shrinkage of adjacent layers. Shrinkage values of layers reinforced by TiB were lower than those for the Ti-alloy, which led to delamination of layered structures, distortion of shape, and cracking. We can control shrinkage in individual layers by means of optimizing the powder size, that allows to obtain multi-layer titanium matrix composites reinforced by TiB with well-balanced mechanical properties.

Biomedical alloys 19Ti-59Zr-22Nb and 40 Ti-35Zr-25Nb were produced by blended elemental powder metallurgy approach using TiH2, ZrH2 and Nb powders. Usage of hydrogen as temporary alloying element for titanium and zirconium leads to activated sintering and decreased residual porosity of the alloys produced. Contrary, large amount of Nb powder negatively affects sintering and 6-9% residual porosity is observed in sintered alloys. Two-stage sintering (TSS) approach which includes preliminary sintering of powder blends, hydrogenation of sintered products, crushed in powder and sintering again, was used to obtain uniform alloys with reduced porosity. Volume changes of sintering of noted powder blends and prealloyed powders were investigated together with microstructure of sintered materials. Using prealloyed hydrogenated powders in TSS process resulted in activated densification, improved homogeneity of alloy microstructures and low (~2%) residual porosity.

This paper proposes the idea of a “small volume” in which to consider complicated processes to create structures in phase transitions of first and second order in the foundry. The small volume is chosen based on the classical theory of crystallization and its use for quantum mechanics. A numerical solution of Stefan-Schwarz’s task was presented by obtaining the temperature field of solidification of a composite cast in a squeeze casting. This little volume we proposed for a good possibility in the direction for a theoretical possibility of hybridization of production and technology.

The base process was obtained: 3D hardening temperature field for the K-test under heat transfer at conditions with maximum intensity. A methodology for determining macro-level defects in aluminum alloys. It is definitely the placement of the K-test method in the process of creating the first order phase transition in a casting technology. The idea of interaction between the classical theory of crystallization and quantum mechanics for the processes of structure formation at casting was introduced by Stefan’s task in volume with nano-size.

The aim of this paper is the investigation of the effect of natural aging on the mechanical, physical and microstructural properties of an EN AW-6060 aluminum alloy. These properties were investigated during different aging treatments. Firstly, the effect of natural aging on properties was investigated, after which the influence of natural aging (room temperature pre-aging) on the artificial aging was studied. The results showed the beneficial effect of natural aging in both sets of experiment. During the natural aging, the hardness increased for around 20 % while electrical conductivity values were slightly higher than in the quenched sample. The hardness of the samples gradually increases up to 25 days of natural aging reaching a plateau state, after which the values of hardness remain the same. Also, room temperature pre-aging had a positive effect on subsequent artificial aging. Samples that were pre-aged for 40 days or more before artificial aging had around a 13 % increase in hardness values compared to the samples that were directly artificially aged. Electrical conductivity had increased by around 1 MS/m in pre-aged samples compared to only artificially aged samples. Optical microscopy investigations confirmed the existence of precipitated phases and their distribution in the microstructure.

The aim of this work is to present the influence of anodic surface treatment parameters on thickness and structure of an anodic layer formed on aluminum products.
The materials used in this study are the aluminum products from Alumil Company in Albania. The analyses of samples were performed using Optical Microscopy (Leica DMI 5000 M) for characterization of macrostructure of anodizing layer and Vickers micro-hardness (HMV-2 tester) of non-anodized aluminum products and anodized aluminum products. Aluminum product of the series A6060 are taken in Alumil Company in Albania. Comparing the results in this research (analyses) we have concluded the characteristics of anodizing layer in the aluminum product, which have improved and increase their surface and product performance.

Equiatomic alloys TiCrFeNiCuC were made by two methods of powder metallurgy – vacuum sintering and hot forging followed by annealing. In the process of sintering the TiCrFeNiCuC blanks, the influence of entropy of mixing resulted in the formation of solid substitution solutions mainly on the basis of the FCC lattice, and also formed titanium carbide (TiC0.74). In samples obtained by hot forging and subsequent annealing, two carbides TiC and Cr3C2 were found, and titanium carbide being formed with lower carbon content (TiC0.58). In addition, the forged samples showed significantly higher values of the defect of the crystalline structure, which leads to increase in their hardness.