Papers by Keyword: Structure

Abstract: The mechanical properties and electrical conductivity of the Al–0.15Fe–0.5Si–0.5Mg–0.2Mn alloy with a Mg/Si ratio of 1 were investigated using optical microscopy, scanning and transmission electron microscopy, tensile testing, Vickers hardness measurements, and specific electrical resistivity measurements. To analyze the electrical conductivity data, the unit % IACS was used, calculated as a percentage relative to the conductivity of annealed copper. The alloy was studied in the as-cast condition, in the deformed condition (following extrusion and drawing), and after heat treatments: HT1 — solution treatment at 530°C and aging at 140°C for 8 hours, and HT2 - solution treatment at 560°C and aging at 175°C for 6 hours. The microstructure of the investigated alloy varied depending on the condition and heat treatment parameters, consisting of an aluminum matrix and strengthening particles with different morphologies and chemical compositions. For rods in the as-cast state, the conductivity was 55% IACS, ultimate tensile strength (UTS) — 150 MPa, and elongation — 14%. After HT1: 51% IACS, UTS — 140 MPa, elongation — 19%. After HT2: 51% IACS, UTS — 195 MPa, elongation — 19%.

Abstract: Using the magnetically controlled electroslag melting method, ingots of the manganese-containing titanium alloy OT4 (Ti–4Al–1.5Mn) were produced from the initial charge components. The as-cast metal was subjected to hot rolling followed by annealing. The chemical analysis showed that the manganese and aluminum content in the ingots matched their levels in the initial charge. No reduction in their concentration in the alloy was detected after single or double remelting. They are evenly distributed along the height and radius of the ingot. The gas content does not exceed the limits established for alloys of this type. Macro-and microstructural analysis of the as-cast and deformed metal did not reveal any pores, cracks, non-metallic inclusions. The mechanical properties of the deformed metal meet the standard requirements for premium-quality OT4 alloy bars. Thus, the conducted research demonstrated the feasibility of producing Ti-alloys with a given content of manganese using magnetically controlled electroslag melting method.

Abstract: Traditional handmade bamboo paper is a commonly used material for the restoration of ancient books and the printing of classic texts. This study discussed the ageing behavior of handmade bamboo paper under dry thermal ageing conditions. The filter paper composed of cellulose serves as a reference example. The results showed that the mechanical properties of bamboo paper containing lignin remained stable for a certain period of time before declining when the pH was less than 7. While the mechanical properties of the filter paper immediately decreased when the pH falls below 7.0. Pore structure analysis indicated that bamboo paper undergoes substantial structural changes in the early stages of aging, with an increase in specific surface area and pore volume, and a decrease in average pore size. These changes then stabilize over time. This may be attributed to the fact that hemicellulose and lignin help maintain the overall integrity of the bamboo paper fibers.The study provides a scientific basis for understanding bamboo paper ageing mechanisms and offers references for preserving historical documents.

Abstract: Steel 22MnB5 is widely used in the automotive industry for manufacturing high-strength structural car body parts. To achieve desired mechanical properties, hot-stamping is used, during which the Al-Si coating plays a critical protective role against oxidation. This study investigates the structural evolution of the Al-Si coating under various austenitization durations at 920 °C. Intermetallic phase formation and coating morphology are analyzed.

Abstract: The objective of this study is to investigate the tribological properties of detonation-sprayed (Ti,Cr)C-Ni coatings under dry and lubricating conditions. The (Ti,Cr)C-based coatings with 25 wt.%, and 33 wt.% of Ni binder were applied onto steel substrates by detonation spraying. Microreciprocating wear tests were performed under dry and lubricating conditions with water, diesel, biofuel, aviation fuel and oil as a lubricating environment. Post-test examination of wear tracks was performed using interference profilometry and SEM analysis. The (Ti,Cr)C-Ni detonation-sprayed coatings exhibit a dense microstructure, featuring well-bonded splats composed of fine (Ti,Cr)C particles and Ni-based binder. The lowest wear rates of the (Ti,Cr)C-25wt.%Ni and (Ti,Cr)C-33wt.%Ni coatings are observed in an oil environment. Instead, the wear rates of both coatings are highest in a water environment. The (Ti,Cr)C-25%wt.Ni detonation-sprayed coating is characterized by an increased wear rate in the water environment as compared with (Ti,Cr)C-33%wt.Ni due to more intensive brittle failure in the water environment.

Abstract: Fatigue damage is one of the key degradation mechanisms affecting the service life and reliability of aluminum alloys in a wide range of technical applications. The present study focuses on the fracture mechanisms of aluminum alloys under cyclic loading, with a view to the initiation and analysis of fatigue crack propagation in the context of the microstructural characteristics of the material. Special attention was paid to the influence of grain morphology, distribution and type of intermetallic phases, as well as the presence of casting defects on the initiation and development of cracks. Fatigue experiments were performed on a selected Al-Mg alloy of the EN AC 51200 type for the use of three-point bending loading. The results show that the key factors affecting the fatigue behavior are the size and distribution of precipitates, the nature of the interfaces between the phases and the occurrence of microcracks initiated mainly in areas of stress concentration. The knowledge gained contributes to a deeper understanding of fatigue mechanisms in aluminum alloys and provides a basis for their optimization in terms of composition and technological processing in order to increase their resistance to fatigue failures.

Abstract: This study aimed to smelt high-entropy alloys (HEAs) composed of inexpensive and commonly available metallic elements using iron-based alloys, ligatures, and commercially pure metals, and to investigate their phase structure and heat-resistance. High-entropy alloys of the FeNiCrCuAl system were smelted in air using an induction furnace with a crucible lined with rammed neutral aluminum and magnesium oxides. The elements Fe, Ni, Cr, Cu, and Al were introduced via high-alloy cast iron, stainless steel grade GX10CrNiMn-18-9-1 (1.4541), industrial-grade low-carbon ferrochrome (FeCr70C1), binary Cu-33Al ligature, tough-pitch copper, and semi-finished nickel. Samples of the investigated alloys were prepared using lost foam and sand mold casting methods. Microstructural analysis revealed the presence of rounded dendritic branches, copper-rich interdendritic regions, and high-chromium carbides. The phase composition of the as-cast FeNiCrCuAl alloys consisted of multiple phases: solid solutions with a BCC structure ordered in the B2 type, an FCC structure, and complex carbides (FeCr)₇C₃. High-entropy alloys of the FeNiCrCuAl system, with increased aluminum and chromium content, can significantly outperform standard heat-resistant stainless steels in terms of oxidation resistance indicators – surface oxidation rate, and oxidation stability at 900°C and 1000°C. The specific oxidation of the high-entropy alloy FeNiCrCuAl, which contains at least 18 at. % chromium, was 0.1627 mg/cm² after a 4-hour exposure at 1000 °C. Under the same conditions, the specific oxidation of X2CrNi19-11 stainless steel (1.4306) was 0.6689 mg/cm².

Abstract: In the presented work the features of formation of metal-fullerene films of the systems Al-C₆₀, Au-C₆₀, Cu-C₆₀, Ti-C₆₀ from atomic-molecular flows in vacuum were investigated, the processes of surface resonance plasmon absorption and diffusion were studied. It is shown that electron microscopy, optical, Auger-electron and X-ray spectroscopy methods are effective for the study of metal-fullerene films. The combination of different methods of spectroscopy and electron microscopy allowed to establish the dependence of the grain size of the films, the shift of the position of the plasmon absorption maximum, diffusion parameters on the ratio of metal and fullerene components, to establish the fact of formation of the chemical compound Cu₆C₆₀.

Abstract: The construction industry is increasingly adopting sustainable solutions, with bamboo emerging as a resilient and eco-friendly material. However, challenges persist in bamboo construction, particularly in developing effective techniques for joining bamboo poles. This study aims to evaluate the structural performance and stress distribution of 3D-printed connectors for bamboo structures. By leveraging 3D printing technology, this research seeks to improve bamboo construction methods addressing its non-uniformity, streamlining design and production, and the potential use of bio-based material. Performance evaluations were conducted through software simulations and digital image correlation (DIC) to assess the mechanical behavior of the connectors and showed 1.561mm and 1.80mm displacement, respectively. The analysis identified areas requiring refinement to enhance load-bearing capacity and optimize stress distribution. The findings suggest that the connectors are explored using different materials, geometry, and even more advanced and efficient design of structures. Furthermore, this study provides practical insights into the viability and sustainability of the integration of 3D printing technology into bamboo construction practices.

Abstract: To improve the toughness of epoxy resins, we add N, N-dimethylformamide (DMF) to epoxy resin as it is curing, and the flexible epoxy resin is prepared. According to the results of Fourier Transform Infrared Spectroscopy (FT-IR), DMF is able to effectively graft onto the epoxy resin. The glass transition temperature (Tg) of the epoxy resin drops from 99.9°C to 19.4°C, indicating a reduction in the thermodynamic stability of DMF/epoxy, according to the results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). According to tensile studies, DMF/epoxy's mechanical strength is decreased, but its elongation is significantly longer and enhanced by three orders of magnitude. Impact testing reveals a significant improvement in the material's hardness (from 1.67 to 15 J·cm^-2). Furthermore, DMF/epoxy is flexibly bendable. Finally, the DMA test shows that DMF/epoxy can achieve good shape memory at low temperatures to room temperature.