The combined effects of wear and creep largely determine the long-term reliability of alloys in demanding thermal and mechanical environments, but conventional structural materials show limited resistance to these degradation mechanisms. High-entropy alloys (HEAs), though inherently robust, have gained attention as potential candidates for such environments, particularly when reinforced with stable oxide dispersions. In this study, oxide-dispersion-strengthened Co-Cr-Fe-Ni HEAs containing 1 and 4 wt% Y2O3 were synthesized through mechanical alloying and spark plasma sintering to evaluate this approach. Microstructural characterization using X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the retention of the fcc crystal lattice. Pronounced grain refinement was achieved, decreasing from 360 +/- 70 nm in the unreinforced HEA to 95 +/- 15 nm in the 4 wt% ODS composition, accompanied by a substantial increase in hardness to 685 +/- 30 HV. Wear experiments revealed a fourfold reduction in specific wear rate. This improvement was accompanied by a transition in wear mode from extensive surface damage in the unreinforced HEA to predominantly oxidative and fatigue-assisted mechanisms in the ODS HEAs, facilitated by the formation of protective tribo-oxide layers. Nanoindentation creep analysis revealed a decrease in stress exponent from 16.05 to 5.72 with increasing Y2O3 content. This change signifies a transition toward dislocation-controlled creep and tunable creep resistance. Collectively, these findings establish that rare-earth oxide dispersion is an effective strategy for simultaneously enhancing surface durability and controlling time-dependent deformation in HEAs, thereby extending their potential for demanding structural and tribological applications.

This study investigates the formation of aluminide coatings on Inconel 718 (IN718) superalloy produced by Cold Spray Additive Manufacturing (CSAM) using Pack Induction Aluminizing (PIA) process. The advantage of the proposed method is that the aluminizing time, which takes several hours in conventional pack aluminizing performed in furnace, can be reduced to a few tens of minutes. The microstructure, phase evolution, and tribological performance of the resulting coating were also characterized in the study. The results showed that increasing the processing time from 5 min to 10 min increased the coating thickness from approximately 10 μ m to 19 μ m, resulting in the formation of a double-layered aluminide coating. XRD and EDS analyses determined that the main components of the coating were aluminum-rich intermetallic compounds with an outer layer of Ni(Fe,Cr)Al _3 and an inner layer of Ni _2 (Fe,Cr)Al _3 , characteristic of a high-activity aluminizing process. The PIA process significantly improved the tribological properties of the IN718 substrate. Specifically, friction coefficient slightly decreased, wear resistance increased, and wear track depth decreased by approximately 80% compared to the uncoated alloy. These findings demonstrate that the PIA method is a highly effective and rapid technique for producing protective, high-performance aluminide coatings on IN718 superalloy fabricated by cold spray additive manufacturing.

This study compares the effect of very fast induction heating for two competitive and cost effective aluminizing process, namely, hot dip aluminizing (HDA) and slurry aluminizing (SA) of Inconel 718 superalloy. Each process produced well adhered coating layers, which comprise two or more layers. Morphological, structural and chemical characterizations of each layer were extensively studied, and formation mechanisms of the coatings were discussed in comparison to each other. The HDA process performed in a molten Al-11 wt. Si bath at 700 °C formed a 120 μm coating layer, mostly comprising of NiAl _3 . The induction heating for 20 s at 1000 °C increased the coating thickness more than two times (250 μm), transformed the aluminides to Ni _2 Al _3 , made the elemental distribution more uniform within the coatings, and also formed CrSi _2 precipitates, which might be beneficial for an improved oxidation resistance. In the SA process, the induction heating forms a coating of 43 μm in thickness, which is more uniform than the HDA coatings, and also comprises of two layers having Ni _2 Al _3 and NiAl type aluminides. EBSD examination revealed that the SA coating has a uniform grain size and random grain orientation, which are promising for improved oxidation resistance. Evaluation of the results in comparison to each other provided a better understanding of the effect of induction heating on different aluminizing processes. For example, a coating uniformity similar to that of the SA coating can be achieved only after the application of the induction heating in the HDA coatings. Also, the SA process assisted with the induction heating can be applied to various substrates without subjected them to a high temperature for a long time, and would be a promising method for partial and complete aluminizing of Ni-based substrates.

In this study, the formation of fast, hard, well-adhered and scratch-resistant in-situ composite coatings on electron beam melted (EBM) Ti-6Al-4V alloy were proposed by successive applications of cold spray (CS) and induction heat treatment techniques. The total treatment time to achieve such properties was around only 5 min. In this context, pure aluminum (Al) was first coated by CS technique on EBM Ti-6Al-4V alloy, and the coated samples were heat treated by induction heating method for different times (10 and 20 s). The coating layer that bonded well to the substrate material was obtained using the CS technique. After the induction heating, TiAl3 intermetallics were formed in a sawtooth-like morphology as an interfacial layer at the substrate-coating interface. Similar to the interface, fiber and plate-like TiAl3 compounds were found within the CS’ed coating layer. As the induction heating time increased to 20 s, the thickness of the interfacial layer and the fraction of intermetallics in the coating layer correspondingly increased. The highest hardness and scratch resistance were obtained in the 20 s induction-heated sample. Finally, this study demonstrates that the cold spray followed by induction heating is a rapid technique to obtain hard, well-adhered and scratch-resistant composite coatings in-situ on EBM Ti-6Al-4V alloy.

This study investigates the wear and high-temperature oxidation behavior of AISI 316L stainless steel (SS) subjected to two distinct aluminizing processes, hot-dip aluminizing (HDA) and slurry aluminizing (SA), both followed by rapid induction heating. The objective was to assess the efficiency of short-time induction heating as a diffusion treatment and to compare the resulting structural and functional properties of the coatings. Microstructural characterization was carried out by using SEM, XRD, and EBSD, while mechanical and tribological properties were evaluated by nanoindentation and wear testing. The HDA coating exhibited a uniform outer morphology, whereas the SA coating developed a lamellar structure due to localized thermal gradients during induction heating. Despite these morphological differences, both coatings consisted of Fe2Al5, FeAl, and α-Fe (Al) phases. The SA coating demonstrated a higher surface hardness (13.2 GPa vs 10.8 GPa for HDA) and a lower coefficient of friction (0.40 vs 0.52), resulting in a markedly lower wear rate (3.2 × 10-5 mm3/N·m vs 6.5 × 10-5 mm3/N·m). Isothermal oxidation at 1000 °C for 24 and 96 h revealed that both coatings transformed toward a protective α-Fe (Al) matrix with a continuous Al2O3 scale. However, the coating thickness increased more significantly in SA samples from 35 to 400 μm after 96 h compared to 230 μm for HDA, indicating superior Al diffusion kinetics in the SA process. Overall, the SA process combined with rapid induction heating exhibited superior wear resistance compared to the HDA route, whereas the HDA process combined with the same thermal treatment demonstrated enhanced oxidation resistance relative to the SA.

As high entropy alloys (HEAs) continue to be increasingly studied for next-generation structural materials, gaining a comprehensive understanding of their mechanical properties, including their creep behaviors, remains essential. In this work, rare earth element yttrium (Y) added CoCrFeNi HEAs are produced by mechanical alloying, followed by consolidation via spark plasma sintering (SPS) with ultrafine grain sizes. The microstructures after SPS consolidation are examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The creep properties, including creep displacement, creep strain rate, creep stress, and stress exponent, are evaluated using a nanoindentation test with a Berkovich tip indenter. The results reveal that the average grain size of CoCrFeNi HEA is determined to be 385 +/- 65 nm after SPS consolidation, which reduces to 190 +/- 30 nm and 155 +/- 55 nm with 1 and 4 at.% Y additions, respectively. Accordingly, HEA with the addition of 4 at.% Y exhibits increased hardness, attributed to the presence of additional Y-based oxides and the reduced grain size in its microstructure. Furthermore, the creep mechanisms for the investigated CoCrFeNi HEAs are primarily dominated by dislocation-precipitation interaction based on the calculated stress exponent values.

This study investigates the wear micromechanisms of D2 steels under impact-sliding conditions, offering insights into their performance when used in applications such as trimming dies for high-strength steel sheets where they undergo plastic deformation and chipping. Two D2 steel samples, both with a bulk hardness of 59.7 HRC but different matrix hardnesses and carbide distributions, are tested by using an impact-sliding wear test rig at Hertzian contact pressures exceeding 2 GPa. The sample with a softer matrix exhibits wear primarily through delamination caused by plastic deformation. This initiates cracks at the matrix/primary carbide interface, leading to material loss in the form of large chips. In contrast, the steel with a harder matrix shows reduced wear due to its resistance to plastic deformation. Initially, wear occurs through the fracture of primary carbides. However, with prolonged loading, the matrix begins to soften, adopting a wear mechanism similar to the D2 steel with softer matrix. Notably, smaller primary carbides are associated with improved wear resistance by limiting the initiation sites for cracks, especially at the matrix/primary carbide interface. This understanding enables the selection and design of heat treatments to optimize D2 steel microstructure, thus improving resistance to impact-sliding wear damages observed in processes like trimming.

OBJECTIVE:This study aimed (1) to simulate pedicle screw pullout after intraoperative external wall perforation and (2) to assess restoration strength with different thread designs in the pedicle screw instrumentation for osteoporotic thoracic vertebrae.METHODS:Twenty fresh-frozen human cadaveric thoracic vertebra bodies were prepared and divided into 4 groups: group 1, 5.5 mm × 45 mm polyaxial single thread pedicle screws (PASTS); group 2, after wall injury 5.5 mm × 45 mm PASTS; group 3, 6.5 mm × 45 mm PASTS after wall injury; and group 4: 6.5 mm × 45 mm polyaxial mixed-threaded screws after wall injury. While group 1 was the control group, groups 2, 3, and 4 were used as study groups after the lateral wall breach. All prepared screw units were placed on a universal pullout measurement testing device.RESULTS:The mean bone mineral density for 20 thoracic vertebrae was 0.57 ± 0.12 g/cm2 (range 0.53-0.6 g/cm2 ). The mean pullout strength was 474.90 Newtons (N) for group 1, 412.85 N for group 2, 475.4 N for group 3, and 630.74N for group 4. The lateral wall breach caused a 14.1 % decrease in average pullout strength compared with the initial screw pullout. Mixed (double)-threaded screws increased pullout strength compared to 6.5 mm screws (P=.036) Conclusion: Using a 1 mm thicker polyaxial pedicle screw or mixed (double)-threaded pedicle screw seems to increase pullout strength; however, this was statistically significant only for group 4. In the thoracic spine, the redirection possibility of the pedicle screw is limited, and augmentation with cement will not be appropriate due to the risk of wall injury-related leakage. Therefore, care should be taken to avoid violating the lateral cortex by using appropriate pedicle entry points and trajectories.

Hot dip aluminizing (HDA) is a surface treatment process in which a metal substrate is coated with a layer of aluminum to enhance its corrosion ad oxidation resistance. However, crack formation can occur during the HDA process possibly due to presence of thermal stresses within the coatings arising from mismatch in thermal expansion coefficients of the aluminide layers and the substrate, brittle nature of the aluminide phases and process parameters. Therefore, optimization of the HDA process parameters such as temperature, dipping time and cooling rate from the dipping temperature might help reducing the possibility of crack formation. Additionally, subsequent diffusion annealing might have an effect on crack formation and overall integrity of the aluminized coating. In this study, an AISI 4140 low alloyed steel was subjected to the HDA process in an Al-11wt.% Si bath at 750◦C for 9 minutes and subsequent annealing was performed at 750◦C, 800◦C and 850◦C. Examination of the diffusion annealed samples indicated that there were some cracks within the coatings of the samples, which were annealed at 750◦C and 800◦C, while there was no cracking on the surface of sample annealed at 850◦C. The results were comparatively evaluated by considering the process parameters and the characteristics of the aluminide layers, and was attributed to the formation of ductile and brittle aluminide phases depending on the applied annealing temperature.

Cold plastic deformations recognizably cause increasing lattice imperfections such as point defects and dislocations in the structure, which could then have an effect on diffusion characteristics of the material. In order to explore such an effect of flow forming, a flow formed AISI 4140 steel and an annealed 4140 steel were subjected to the HDA process in a molten Al7020 bath at 750◦C for 4 min, and a subsequent diffusion annealing was performed at 800◦C, and their coating characteristics such as coating thickness and hardness were compared. The results indicated that the coating thickness of the flow formed samples was higher (80◦m) than that of the annealed sample (50◦m) after the HDA process. Diffusion annealing increased the coating thickness of both samples five times, reaching 400◦m and 250◦m for the flow formed and the annealed samples, respectively. Comparing the measured thickness of the coatings revealed that flow forming accelerates diffusion during the HDA process, probably due to the defect structure induced by the flow forming. On the other hand, the coating hardness was in between 1000-1100 HV for both samples, implying that the initial condition of the sample does not have a remarkable effect on hardness after the HDA process.

This study examines the development of architectural education in the information age, particularly concerning the representation and expression of knowledge. Considering that architecture is a visual medium that aims to construct tangible structures, it remains in constant flux due to changing environmental conditions, architects, and technology. Interdisciplinary studies have revealed that visual tools like diagrams effectively transfer knowledge and practice. This study focuses explicitly on the role of architectural diagrams in facilitating communication and enabling architecture students to express their design knowledge. It examines diagrams’ characteristics, functions, and potential for representing architectural designs. Within the scope of the study, the transfer of architectural knowledge, the means through which it is communicated, the effectiveness of diagrams as a means of expression in the field of architecture, how they are used in the educational environment, and the competencies of understanding and using diagrams were questioned through a survey conducted with architecture students in the city of Kayseri. Students’ attitudes in three universities in Kayseri are evaluated to understand how architectural education adapts to the current environment.

AZ91 Mg alloy has a wide range of applications in the automotive industry, although its use is restricted to powertrain applications due to its low creep resistance. In this study, the effect of the micro arc oxidation (MAO) coating on the creep resistance of an AZ91 Mg alloy was investigated to take advantage of the coating layer with high thermal insulation properties. In this context, the MAO process was applied to AZ91 Mg alloy using a bipolar pulsed DC power supply. The creep tests were conducted at different temperatures (150-200 degrees C) and stresses (25-90 MPa) for the bare and coated samples, and the minimum creep rates were determined. It has been shown that the MAO coating reduces the creep rate of the bare alloy by 35%-84% depending on the temperature and the stress due to the stress-reducing effect and thermal barrier properties of the MAO coating. Based on the calculated creep activation energy and stress exponents, creep mechanisms were proposed for the bare and coated alloys. Effective activation energy was also calculated and lattice diffusion-controlled dislocation climb was determined to be the effective creep mechanism for both samples at lower stresses, while pipe diffusion controlled dislocation climb was effective at higher stresses.

Abstract This study was conducted to understand the creep behavior of two oxide dispersion strengthened alloys containing Zr as the alloying addition by performing indentation creep tests at room temperature. The oxide dispersion strengthened alloys were Fe–8Ni–xZr (x = 1 and 4 at.%, i.e., Zr-1 and Zr-4 alloys, respectively), which had been previously fabricated by mechanical alloying; followed by consolidation via equal channel angular extrusion at 1000 °C. The indentation tests were conducted under a maximum load of 100 mN with the loading rates at 300 and 400 mN min−1. The hardness was calculated by the Oliver–Pharr method, and the creep properties, such as the creep displacement, creep strain rate, creep stress, and stress exponent n, were determined. The results showed that the Zr-4 alloy was harder than the Zr-1 alloy. However, the creep resistance of the Zr-1 alloy was better than that of the Zr-4 alloy. It was further demonstrated that both the hardness and creep resistance depended on the loading rate. Moreover, a possible creep mechanism was proposed. Although the tests were performed at room temperature, they can provide insight into the effect of an oxide dispersion strengthened alloys microstructure on creep at higher temperatures.

Arrays of TiO2 nanotubes were prepared on pre-deformed commercially pure titanium (Cp-Ti) foils by anodic oxidation in 1 vol.-% HF-based electrolyte. Prior to the anodic oxidation, the samples were deformed by uniaxial tension and cold rolling at room temperature in three different strain levels. Following the anodic oxidation, the samples were annealed at 450 degrees C to obtain crystalline anatase structure. Effects of the deformation on the produced nano structures were investigated by characterisation studies and photocatalytic activity tests including methylene blue degradation test, photoluminescence, and UV-Vis diffuse reflectance spectra analyses. The results showed that the induced strain has a remarkable effect on the nanotube morphology. It also led to a decrease in the crystallite size in the uniaxial tensioned and cold rolled titanium foils. As a result of the morphological and structural changes, the photocatalytic activity of the samples increased with cold rolling strain, and uniaxial tension strains up to a critical level.

According to the 2021 data from the International Energy Agency, educational buildings had the highest energy consumption after residential and office buildings. The number of schools affiliated with the Republic of Turkey Ministry of National Education (MoNE) is 67,125 and the number of users is over 20 million (preschool, primary school, secondary school), which is increasing daily. Providing adequate lighting and visual comfort conditions increases education quality and is favorable for health. In educational buildings, energy consumption can be saved by changing space usage with different education models, changing/transforming spaces with the re-quirements of the age, and optimizing space-related design conditions. Educational guidelines published by different institutions and organizations in various countries emphasize the importance of sustainable lighting conditions in educational buildings. In the guideline published by MoNE in 2015, it is not possible to optimize the energy required for lighting with the standardized building type according to different climate zones. Natural lighting conditions need to be investigated in detail with other issues such as space characteristics (size, furnishing, function, window size, etc.), latitude, sunshine duration, climate, direction, orientation, etc. Educational buildings, which have been produced as a uniform project in Turkey in recent years, need to be re-evaluated according to the physical and psychological needs of the users, architecturally flexible uses, building performance, and energy-efficient use according to different climate zones. This article aims to analyzing the daylighting standards in educational buildings and regulations that are applied internationally to define a set of rules that could be applied in Turkey to supplement the local legislation.

The electrical and mechanical properties of carbon fiber-reinforced polymer (CFRP) composites have a close dependence on the use of modifiers like polyvinylpyrrolidone (PVP), as well as on the processing techniques to disperse functional charges such as graphene-related materials into the epoxy base. In the present work, reduced graphene oxide (RGO), prepared by a natural antioxidant agent, astaxanthin, was used as a filler material in the epoxy matrix of the carbon fiber composites. The astaxanthin reduction leads to an increase in the sp 2 ordering in RGO; some residual epoxy and C-O groups that enhance the interaction with the epoxy matrix remain after reduction. The effects of RGO and PVP-modified RGO (PVP-RGO) fillers with different contents (0.05, 0.1, and 0.15% wt.) on the electrical conductivity, bending properties, and dynamic mechanical properties of CFRP were investigated. The incorporation of 0.15 wt.% RGO with and without PVP-modification, leads to through-the-thickness (Z-direction testing) conductivity values 7.4 and 9.6 times higher than those of the neat composite, respectively. The conductivity tests indicate that the RGO/epoxy composite behaves as a continuous conductor due to the formation of agglomerates of RGO within the matrix, while at the added contents of the PVP-RGO filler, the composite is below the percolation threshold, then conducting by electron tunneling, due to a better dispersion of the PVP-RGO filler within the epoxy matrix. The dynamic mechanical analysis shows that the glass transition temperature is indicative of the interactions among the filler, the epoxy matrix, and the carbon fiber, that is, the PVP-RGO filler increases the chain mobility due to its higher dispersion in the matrix. While T g of the neat epoxy/CFRP composite is 92.5°C, a minimum T g of 88.5°C was achieved with a 0.10 % wt. PVP-RGO filler contents, and a maximum T g of 94.5°C with a 0.15 % wt. of RGO filler amount. For constant filler content (0.15 wt.%), CFRP composite containing RGO and PVP-modified RGO exhibited 9.73% and 13.87% increase in flexural strength values, respectively, compared to the neat composite. The bending test revealed that PVP modification to RGO is beneficial to improve flexural strength of CFRP composites.

Arrays of titanium dioxide (TiO 2 ) nanotubes were prepared on commercially pure titanium (Ti) foils by anodic oxidation in a 0.5 M hydrofluoric acid (HF)-based electrolyte with multiwalled carbon nanotubes (MWCNTs) up to 0.035 g/l. The samples were annealed at 450°C for 1 h after anodic oxidation to form a crystalline anatase structure. The effect of MWCNT addition on the morphology and photocatalytic activity of the nanostructures was characterized by scanning electron microscopy, Raman spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence spectroscopy and methylene blue degradation tests. The results showed that MWCNTs were successfully incorporated into the titanium dioxide nanotube structure and significantly affected its photocatalytic activity. The best photocatalytic performance was achieved with the use of 0.025 g/l MWCNTs in the electrolyte composition. However, when the MWCNT content in the electrolyte increased, the electron–hole recombination rate and photon absorption ability of the structure deteriorated, resulting in a decreased photocatalytic activity.

In this study, graphene nanoplatelets (GNPs) added to epoxy matrix composite reinforced by aeronautical grade carbon fibers (CFs) were fabricated by the vacuum infusion method, and the effect of different GNPs contents (0.05, 0.25, and 1.25 wt%) on electrical conductivity, flexural properties, and dynamic mechanical properties were investigated. The results revealed an 8- and 73-times improvement in conductivity values across the thickness with the addition of 0.05 and 0.25 wt% GNPs, respectively, compared to the neat composite. Flexural test results showed that with the addition of 0.05 GNP, only 6% increase in flexural strength was obtained, while with the addition of 0.25 wt% GNP flexural strength remained almost the same as for the neat composite. On the contrary, the addition of GNPs (1.25% by weight) causes a reduction in the flexural strength with respect to the neat composite. This was confirmed by the fractured surfaces examined by scanning electron microscope which reveals that considerable amount of fiber-matrix debonding was observed with 1.25 GNPs loading. Dynamic mechanical analysis (DMA) revealed that the storage modulus of the neat composite increased by 12.6% with the addition of only a small amount of GNP (0.05% wt) compared to the neat composite. Composite with 1.25 GNP shows upward bending, affecting the shape of the cole-cole plot obtained from DMA results, indicating inappropriate interactions of GNPs in both the matrix and CF in the composite.

In this study, in-situ oxide dispersion strengthened (ODS) Fe91Ni8Zr1 and Fe88Ni8Zr4 alloys were produced by combination of high energy mechanical alloying (HEMA) and high temperature equal channel angular extrusion (HT-ECAE). The wear behaviors of the consolidated samples were investigated under different loads from 1 N to 4 N by reciprocating wear tests at room temperature. The Scanning electron microscopy (SEM) was used to examine the wear tracks to analyze the wear characteristics as a function of applied loads. The relative comparison of the wear results showed that under the lower loads of 1 N and 2 N, Fe88Ni8Zr4 alloy has lower wear rate than Fe91Ni8Zr1 alloy whereas under the higher loads of 3 N and 4 N, it is vice versa. Additionally, the friction coefficient of Fe91Ni8Zr1 alloy was found to be lower than that of Fe88Ni8Zr4 alloy under all the applied loads. The results were comparatively discussed with respect to microstructural features of 1 at% Zr and 4 at% Zr containing ODS alloys produced by HEMA followed by ECAE. The obtained results of ODS alloys with different grain size, precipitate size, and number density of the precipitates, may disclose a new sight for using such alloys in wear applications just as cutting tools, turbine blades, and discs.