Key Engineering Materials Vol. 1046

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: 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: The paper deals with an experimental determination of the temperature dependence of the contact angle of wetting of the tungsten substrate by liquid tin using the sessile drop method. Unlike the traditional method of heating of one drop of melt on a solid substrate, here a new similar drop of liquid tin was supplied through the capillary as the temperature increased. It was found that the values of the contact angle decreased with the growing temperature, but these values increased again at higher temperatures. Our findings indicate that, as applied to the tin–tungsten system, the curve of temperature dependence of the contact angle shows the sections of an anomalous increase in values of the contact angle as the temperature rises. We observed this effect earlier in the tin–steel system, and it was given a theoretical explanation from the standpoint of the quantum-mechanical model of Wentzel–Kramers–Brillouin quasiclassical representations.

Abstract: Applications of advanced heat resistant ferritic steels in boiler repairs require detailed information on the creep behaviour of welds made of various combinations of steels. The paper deals with the results of hardness and microstructure characterization of a dissimilar circumferential weld of 14MoV6-3 and P91 tubes after about 10 years of service exposure in a boiler operated at 580 °C and steam pressure of 10.3 MPa. The P91 tube (f38x4 mm) was welded to the 14MoV6-3 tube (f38x6.3 mm) using the GTAW (141) technology. Bőhler-FOX IN 9-IG (3Cr0.5Mo0.3V) wires were applied as a filler material. Microhardness evaluation after long-term service exposure revealed two carburized zones, values in these zones did not exceed 350 HV0.5. The slowdown of recrystallization in partially decarburized areas of the 14MoV6-3 and the WM suppressed the formation of soft ferritic bands along fusion lines. This phenomenon is related to the high thermodynamic stability of V(C,N) particles in vanadium-bearing low alloy heat resistant ferritic steels at temperatures below 600 °C.

Abstract: This study presents the results of both non-destructive (radiography and computed tomography) and destructive (light optical and scanning electron microscopy) evaluations of operational degradation in welded joints of ESW (electroslag welding) pipelines. Microbiologically influenced corrosion (MIC), potentially induced by manganese-oxidizing microorganisms (MOMOs), was investigated as a plausible degradation mechanism. Extensive subsurface corrosion cavities were identified beneath the internal surface of the pipelines. The presence of MnO₂ globules near these cavities supports the hypothesis of MOMO-induced corrosion.

Abstract: Alumina dispersion strengthened copper (ADSC) is nowadays well-researched material. Its properties make it an excellent candidate for use in electrical engineering applications such as material for welding electrodes. The subject of this study was a joint of ADSC and precipitation-strengthened Cu-Cr alloy. ADSC was prepared by powder metallurgy method using Spark Plasma Sintering (SPS). While SPS allows the preparation of low porosity compacts it's limited by the size and shape of compacts it can prepare. This work aimed to prepare different joints between ADSC and Cu-Cr alloy and examine their properties as well as chemical composition and microstructures. Three types of joints were tested. A joint made by pressing ADSC into Cu-Cr sleeve shows the forming of oxides in the joint as well as the hardening of Cu-Cr on the contact surface due to deformation strengthening. Joint made by SPS flash sintering showing the formation of relatively big cavities and the formation of oxides on the materials interface. The in-situ joint was produced using a method where a Cu-Cr sleeve replaced the bottom punch in SPS compaction. The In-situ interface shows very little change in chemical composition and seemingly made a diffusion connection. However, these samples show higher porosity of composite compared to regularly SPS prepared compacts.

Abstract: The structural vulnerability of rural dwellings built with traditional adobe in high Andean areas motivates the search for sustainable solutions that improve their mechanical properties without increasing costs. This study evaluates the mechanical behavior of adobe blocks reinforced with natural fibers such as sheep wool and corn husk, locally available agricultural waste. Five types of blocks were created, varying the wool content (0.2%, 0.4%, and 0.6%) with a fixed proportion of husk (0.6%), while traditional mixtures with ichu as a reference were used. Standardized compressive and flexural strength tests were performed, identifying the mixture with 0.4% wool and 0.6% husk as the most efficient, achieving average values of 1.83 MPa and 0.81 MPa, respectively. These results exceed traditional blocks by more than 47% and 34%, demonstrating a significant improvement in structural performance. Analysis of the mixture confirmed its viability as a low-cost material for rural areas, improving the mechanical properties of adobe and offering an ecological and replicable alternative for housing in extreme climates.

Abstract: Rapid urbanization, economic expansion and population growth have led to a significant increase in global solid waste production, which threatens ecosystems, depletes natural resources, and negatively affects human health. Textile waste has reached 150 million tons per year and constitutes a significant portion of this growing waste stream. At this point, interest in the use of recycled materials as an alternative raw material has increased, and composite materials have emerged as a promising area for the evaluation of textile waste, offering sustainable solutions for resource recovery and waste management. In this study, hybrid composites are developed by introducing various fibrous waste groups (denim and human hair) and bio-resin (acrylated epoxidized soybean oil, AESO) to E-glass reinforced epoxy composites, and the effects of waste type and bio-resin addition on the flexural strengths of the structures are examined using a full factorial experimental design. In this regard, three different sandwich structures are designed, with the outer layers made of E-glass woven fabric and the middle layers made of either E-glass fabric for control samples or different waste groups, and the productions are carried out using the vacuum infusion method. Pure epoxy or an epoxy system with 30% AESO additive is used as matrix material. Statistical results indicate that reinforcement type has a huge effect on the flexural properties individually and in binary interactions of of other factors. The performance results show that the flexural strength is improved with addition of waste regardless of their type and the best flexural properties are seen in samples with denim waste reinforcement containing cotton fiber, while the addition of AESO appears to have a negative effect. The composite structures developed within this study have the potential to replace particle boards, thus contributing to solid waste management and producing innovative solutions to resource scarcity.

Abstract: Today, the solid waste problem is expanding at an alarming rate, and considering the scale of production and consumption, the textile industry contributes significantly to this waste. An indispensable component of fast fashion, polyamide-containing pantyhose are included in the disposable product group and cause irreversible loss of a very valuable raw material. The waste of this product group constitutes a hidden waste group that does not decompose in nature and has not yet been recycled. This study focuses on recycling polyamide-containing pantyhose waste and evaluating them in thermal insulation panel production. In this context, the process of opening the fibers of the pantyhose is carried out in a carding machine, and a hot press technique is utilized with the addition of low melting temperature polypropylene fibers as a binder, for panel production. Rice husk, which is a commonly known agricultural waste, is also introduced into the panels in different forms (granule and powder) for better air encapsulation. The effect of ply number (two and four) and the form of rice husk added as an additive on thermal and air permeability properties is examined within the framework of a full factorial experimental design plan. The findings obtained reveal that the variables affect both thermal insulation and air permeability properties both individually and in binary interactions. The lowest thermal insulation coefficient is obtained in the two plied, granule form rice husk added sample group (0.02117 W/mK), which also has the highest air permeability values (442.57 l/m²/s) and the results are found to be competitive with commercial products. This suggests that it is possible to use this waste group in sustainable panels for construction, and the findings reveal that it may create value in terms of both solid waste management and exploring new resources for polyamide-based fibrous products.