Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Kök, Mediha(4)
- Taşgın, Yahya(4)
- Güler, Ömer(3)
- Islak, Serkan(3)
- Kanca, M. Sait(3)
- Qader, Ibrahim Nazem(3)
- ALMisned, Ghada(2)
- Aslan, Naim(2)
- Ilkiliç, Cumali(2)
- Kahraman, Gökhan(2)
- Kanca, Muhammed Sait(2)
- Tasgin, Yahya(2)
- Tekin, H.O.(2)
- Çelik, Ertugrul(2)
- Çelik, Ertuğrul(2)
- Özkul, İskender(2)
- Akgül, Melek(1)
- Aksakal, Bunyamin(1)
- Aksakal, Bünyamin(1)
- Aydoğdu, Kumruya(1)
- Balci, Esra(1)
- Camgoz, Berkay(1)
- Canbay, Canan Aksu(1)
- Cihangir, Salih(1)
- Coşkun, Meltem(1)
- Danacı, Hacer Cemre(1)
- Dehghanpour, Heydar(1)
- Dilek, İlhan(1)
- Doğan, Fatih(1)
- Durmus, Hasan(1)
- Ergin, Ramazan(1)
- Etli, Serkan(1)
- Fidan, Ferzan(1)
- Gueven, A.(1)
- Güler, Seval Hale(1)
- Gürgenç, Turan(1)
- Hansu, Osman(1)
- Hicsasmaz, Z.(1)
- Houssain, Hasaneen(1)
- Islak, S.(1)
Yayınlar
- MakaleAçık Erişim2026Scopus SJRQ2Comparative Microstructural, Mechanical, and Tribological Evaluation of Cu Matrix Composites Reinforced with B4C, B, Cr, Co, Al2O3, and Graphite via Powder Metallurgy
Macit, Cevher Kursat; Gürgenç, Turan; Aksakal, Bunyamin; Aslan, Naim
Copper and its alloys are widely used in electrical, automotive, aerospace, and energy applications because of their excellent thermal and electrical conductivity. However, the low hardness and poor wear resistance of pure Cu limit its use under tribologically demanding sliding conditions. In this study, Cu matrix composites reinforced with 1 wt.% boron carbide (B4C), boron (B), chromium (Cr), cobalt (Co), alumina (Al2O3), and graphite (Gr) were fabricated by powder metallurgy and comparatively evaluated under identical processing and testing conditions. Phase constitution and microstructural characteristics were analyzed by XRD, SEM, and EDS, while mechanical and tribological behavior was assessed by Vickers hardness and dry sliding wear tests. All reinforcements improved the hardness of the Cu matrix compared with unreinforced Cu. The hardness increase followed the order Cu–B4C (68.91%) > Cu–B (66.43%) > Cu–Gr (63.97%) > Cu–Al2O3 (61.79%) > Cu–Cr (42.69%) > Cu–Co (36.04%). Dry sliding wear tests, performed under a 10 N normal load, 0.05 m s−1 sliding speed, and 1000 m sliding distance against a 316L stainless-steel ball, showed that all reinforced composites exhibited lower mass loss and more stable sliding behavior than pure Cu. Among all samples, Cu–B4C displayed the best wear performance, with a 154.8% improvement in wear resistance relative to pure Cu. SEM analysis of the worn surfaces revealed that reinforcement addition reduced severe plastic deformation, groove formation, and delamination, leading to a more stable wear regime. Graphite- and boron-containing composites benefited from interfacial lubrication and contact stabilization, whereas B4C and Al2O3 improved wear resistance through rigid-particle strengthening and enhanced load-bearing capacity. By comparing ceramic, metalloid, metallic, oxide, and solid-lubricating reinforcements at the same low addition level and under identical processing and testing conditions, this study provides a reinforcement-selection framework for Cu-based composites requiring improved hardness and dry-sliding durability.
AtıfScopus2WoS2OpenAlex2
İncele - MakaleYalnız künye2026Scopus SJRQ1Engineering Ti-Zr-Hf high-entropy alloys (HEA) with rare-earth and boron additives for microstructure-controlled mixed-field radiation shielding: Fabrication, physical, structural and experimental γ-ray & fast-n shielding properties
Özkul, İskender; Güler, Ömer; Kavaz, E.; Kalay, Ece; Güler, Seval Hale; ALMisned, Ghada; Tekin, H.O.
This study investigates three newly designed Ti-Zr-Hf-based high-entropy alloys such as TiZrHfGdSm (N1), TiZrHfEr (N2), and TiZrHfGdEuB (N3), with the aim of understanding how selected rare-earth and boron additions influence microstructural evolution and dual γ-ray/fast-neutron shielding performance. All alloys were synthesized by arc melting and evaluated through thermodynamic modelling, X-ray diffraction, scanning electron microscopy with elemental mapping, and mixed-field attenuation measurements. The results show that each composition forms an HCP-type solid-solution matrix with composition-dependent lattice distortion and secondary phase formation. Among the studied systems, the Er-modified alloy N2 develops the most spatially uniform elemental distribution and demonstrates the most balanced combination of γ-ray attenuation, effective atomic number, buildup behaviour, and fast-neutron removal efficiency. N1 and N3, containing multiple rare-earth elements and, in the case of N3, boron-induced borides, exhibit distinct grain features and provide valuable insights into how multi-element additions shape photon and neutron interaction pathways. Comparative examination confirms that shielding performance in these HEAs is governed by the interplay of elemental cross sections, density, and microstructural uniformity. The findings highlight Ti-Zr-Hf-RE(B) alloys as promising platforms for multifunctional radiation-shielding materials and provide a compositional framework for future optimization in nuclear, medical, and aerospace applications.
AtıfScopus2OpenAlex2İncele - MakaleYalnız künye2026Scopus SJRQ2Influence of Low-SiC Content on the Tribological and Electrical Properties of Cu Composites Produced by Spark Plasma Sintering
Çelik, Ertuğrul
In this study, copper matrix composites reinforced with varying silicon carbide (SiC) contents (0.25, 0.5, 0.75, and 1 wt.%) were fabricated using spark plasma sintering (SPS). The effects of SiC reinforcement on the microstructure, hardness, porosity, electrical conductivity, and tribological performance were systematically investigated. Brinell hardness values increased with higher SiC content, reaching up to 76 HB for the 1 wt.% SiC composite. This improvement was accompanied by a gradual increase in porosity from 0.6 to 2.1%. Electrical conductivity decreased from 93% IACS to 66% IACS with increasing SiC content. Tribological tests revealed that the specific wear rate was significantly reduced, reaching as low as 1.1 × 10−4 mm3/N m at 15 N due to the formation of a protective tribolayer. These results demonstrate that incorporating small amounts of SiC can substantially improve hardness and wear resistance, while maintaining acceptable electrical performance, making Cu-SiC composites promising candidates for durable electrical contact applications.
AtıfScopus1WoS1OpenAlex1İncele - MakaleYalnız künye2026Scopus SJRQ3Bioactive compounds in mucus and shell microstructure of the European ear snail (Radix auricularia)
Kocabaş, Kutluyer; Kocabaş, M.; Kizak, V.; Korkmaz, B.
Radix auricularia is a non-native and invasive freshwater snail species and it may have destructive impacts on biodiversity and ecosystem structure. In recent years, snail mucus, as a sticky substance, has garnered significant attention in the medical and cosmetic industries due to its content of numerous bioactive compounds. Despite frequently being discarded as waste due to the build-up of calcium carbonate crystals through biomineralization, shells of freshwater snail serve multiple functions in aquatic environments and have potential industrial applications. Hence, this study aims to identify bioactive compounds in the mucus and analyze the shell microstructure and mineralogy of the European ear snail (Radix auricularia). Bioactive constituents of mucus were characterized by Gas Chromatography-Mass Spectrometry (GC-FID-MS) analysis. We also conducted analyses on the organic matrix of shells from R. auricularia using X-ray diffraction (XRD) and Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS). Our results indicated that ten compounds are characterized by Eicosane (34.16%), 9-Octadecen-1-ol, (Z)-(11.86%) and N,N-Dimetylpalmitamide (5.55%) as the main components of mucus. The antioxidant potential, antifungal and anti-inflammatory properties of Eicosane was in notable quantity in the mucus. In addition, the elemental composition of shell powder comprised of carbon, aluminium, oxygen, calcium, iron, magnesium, silicium, manganese, sodium, sulphur and phosphorus. Aragonite emerged as the dominant mineralogy in the inorganic layer of their shells, as confirmed by XRD. Overall, individual compounds of mucus could be isolated and purified mucus compounds could have applications in pharmaceuticals and health sectors. The shells of R. auricularia offer potential for diverse applications and contribute to environmental sustainability as valuable biomaterials.
- MakaleYayıncıda açık erişim2026Scopus SJRQ1Tailoring of Dy2O3-B4C hybrid-reinforcements in Fe-Co-Ni-Cr-W High-Entropy Alloy (HEA) matrix for correlating structural, mechanical, and experimental gamma-ray transmission behaviour
Özkul, İskender; Güler, Ömer; Camgoz, Berkay; ALMisned, Ghada; Yaprak, Gunseli; Tekin, H.O.; Durmus, Hasan
This study investigates the structural, mechanical, and experimental gamma-ray attenuation properties of Fe-Co-Ni-Cr-W high-entropy alloy (HEA) composites reinforced with varying concentrations of Dy2O3 and B4C. A series of samples (S0-S4) was synthesized via vacuum arc melting to evaluate the synergistic effects of rare-earth oxide and carbide additions on a stable multi-component matrix. Thermodynamic assessments confirmed that the base alloy aligns with solid-solution formation criteria (1.61R configurational entropy, Ω = 10.33), which was experimentally validated by XRD patterns revealing a consistent FCC crystal structure across all compositions. SEM-EDS mapping further verified the successful integration of reinforcements as discrete secondary phases within the HEA matrix. Mechanical characterization showed that ceramic incorporation significantly enhances the hardness of the monolithic HEA, with the hybrid-reinforced S3 sample achieving a peak value of 628 HV. This improvement is attributed to the combined effects of oxide dispersion strengthening and microstructural refinement induced by B4C. Experimental gamma-ray transmission tests, conducted using a high-purity germanium (HPGe) detector in the 276-383 keV energy range, demonstrated that the S3 configuration provides the most efficient shielding performance, characterized by the lowest transmission factors. Interestingly, the results suggest that beyond an optimal threshold, increased reinforcement loading, as seen in S4 sample, may lead to minor performance trade-offs due to phase distribution dynamics. The findings highlight that the development of multifunctional HEA-based shields requires a delicate balance between reinforcement volume fraction and microstructural homogeneity to maximize both structural and shielding efficiency.
AtıfOpenAlex1İncele - MakaleAçık Erişim2026Scopus SJRQ2Pressure-induced transformation in NiTi-CuAg shape memory alloys: investigation of microstructural and thermodynamic changes
Tatar, Cengiz; Kök, Mediha; Kanca, M Sait; Balci, Esra; Qader, Ibrahim Nazem
Shape memory alloys (SMAs), particularly nickel-titanium (NiTi) based systems, are widely recognized for their unique shape memory effect and superelastic behavior, driven by reversible martensitic phase transformations. To enhance these functional properties for advanced applications, alloying with elements such as copper (Cu) and silver (Ag) has been explored. This study investigates the synthesis and characterization of a novel quaternary NiTiCuAg shape memory alloy. The alloy was fabricated via arc-melting from high-purity elemental powders, followed by application of varying uniaxial compressive pressures to assess their effects on phase transformation behavior. Thermal, structural, and microstructural properties were evaluated using Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy coupled with Energy-Dispersive x-ray Spectroscopy (SEM-EDX), and x-ray Diffraction (XRD). The results aim to elucidate the combined effects of compositional tailoring and mechanical processing on the functional performance of NiTiCuAg SMAs, with implications for their use in high-performance, pressure-sensitive applications.
- MakaleAçık Erişim2026Scopus SJRQ2Investigation of the Mechanical and Metallographic Effects of Adding 2-3% Al-Ti-Mo Elements to High-Entropy CoCrFeNi Alloys
Dilek, İlhan; Taşgın, Yahya; Kanca, Muhammed Sait; Kök, Mediha; Güler, Ömer
Recently, high-entropy alloys (HEAs) have attracted significant attention due to their unique multicomponent composition and exceptional mechanical properties, such as high wear and corrosion resistance, making them superior to conventional alloys for advanced engineering applications. The effects of Al, Ti, and Mo addition on the microstructural and mechanical properties of CoCrFeNi-based HEAs were investigated. The alloys were produced via powder metallurgy and vacuum arc melting, with the addition of 2 and 3% Al, Ti, and Mo, respectively. Scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD) were used to perform microstructural characterization, while microhardness and wear tests were used to evaluate mechanical performance. The addition of Al and Ti enhanced the face-centered cubic phase stability and increased the hardness by improving the lattice structure. In contrast, the addition of Mo contributed to solid solution and precipitation hardening, resulting in a simpler microstructure and superior tribological performance. Among all compositions, the alloy with 3% Mo addition exhibited the highest hardness value (≈ 233.8 HV) and the lowest mass loss (4.3 mg) was observed, indicating a significant improvement in the wear resistance and mechanical strength. In conclusion, the addition of Ti and Mo to CoCrFeNi HEAs promotes solid solution, precipitation, and grain boundary hardening mechanisms, thereby enhancing microstructural integrity, hardness, and wear resistance. These findings suggest that such alloys are promising candidates for use as next-generation structural and tribological materials under demanding operational conditions.
- MakaleYalnız künye2026Scopus SJRQ2Oxide Dispersion, Microstructure, and Functional Evolution in La2O3 Modified Cu-Al-Mn-Fe Shape Memory Alloys
Karaduman, Oktay; Doğan, Fatih; Dehghanpour, Heydar; Yüzüak, Gizem Durak; Yüzüak, Ercüment; Canbay, Canan Aksu
Cu-Al-Mn-Fe high-temperature shape memory alloys containing 0-1.0 wt.% La2O3 were fabricated by vacuum arc remelting to investigate oxide-dispersion effects on microstructure, martensitic transformation, wear, and corrosion behavior. XRD and SEM analyses revealed that low La2O3 additions (0.2-0.4 wt.%) promoted β1′ martensite refinement and enhanced crystallinity, while higher contents induced structural heterogeneity. The alloy with 0.4 wt.% La2O3 exhibited the highest transformation enthalpy (7.49 J g−1), reduced friction coefficient (~0.55), and the narrowest wear scar (~501 µm). Electrochemical tests in 3.5 wt.% NaCl showed a fivefold decrease in corrosion current density and increased charge-transfer resistance (2512 Ω cm2) for the same composition. Excessive La2O3 led to performance degradation due to particle agglomeration and interfacial defects. The results demonstrated that controlled La2O3 addition enabled microstructural refinement and multifunctional performance enhancement in Cu-based shape memory alloys.
- MakaleAçık Erişim2025Scopus SJRQ2Effects of ZrN and DLC coatings on morphostructural, corrosion, cell viability, and antibacterial properties of Ti6Al4V scaffolds
Aslan, Naim; Aksakal, Bünyamin; Cihangir, Salih; Fidan, Ferzan; Yilmazer, Yasemin
Lightweight and functional metallic materials are consistently favored and attract significant attention in the biomedical field. This study investigates the influence of ZrN and DLC coatings on Ti6Al4V scaffolds with varying porosities (40%, 50%, 60%) for biomedical applications. PVD-deposited coatings exhibited distinct growth mechanisms: High-resolution SEM-FIB analyses revealed columnar ZrN structures due to limited adatom mobility, while DLC formed conformal, amorphous layers via high-energy carbon species. Corrosion resistance decreased in 40% porous DLC and 60% porous ZrN-coated samples, likely due to coating defects and increased electrolyte access through open pores. ZrN coatings showed superior antibacterial activity and attributed to surface reactivity and potential ion release. In contrast, the uncoated 60% porous scaffolds demonstrated highest cell viability, suggesting that excessive coating on highly porous structures may hinder cell–material interactions. Furthermore, the cytotoxicity evaluations indicated that uncoated scaffolds exhibited the highest cell viability (77.51%) at 60% porosity after 48 hours, with ZrN coatings demonstrating better efficacy compared to DLC in the 50% and 60% porosity groups.
AtıfScopus3WoS3OpenAlex3İncele - MakaleYalnız künye2024Scopus SJRQ2Investigation of thermal, crystal and magnetic behavior of addition of Nd rare earth element effect on CuAlMn shape memory alloy
Kanca, Muhammed Sait
In this study, CuAlMn alloys, a popular Cu-based shape memory alloy, were chosen because they exhibit superior shape memory properties and improved ductility compared to other Cu-based SMAs. The rare earth element Nd (neodymium) was added to CuAlMn alloy at the specified atomic percentages in the composition Cu70-xAl24Mn6Ndx(x = 0,2,4,8) and their thermal behavior, crystal structure, surface morphology and magnetic properties were investigated after fabrication. As a result of the thermal analysis measurements, it was observed that for low Nd ratios, the austenite phase transformation initial temperature of the CuAlMn alloy was increased, while at high Nd ratios, a decrease in the shape memory property was detected. Martensitic phase and precipitate phase α phase were observed in the crystal structure properties of CuAlMn alloys without and with Nd doping. These results were also detected in surface morphology observations. In addition, the crystal size decreased from 135 to 105 nm with Nd doping. As a result of magnetic measurements, CuAlMn ternary shape memory alloy was found to be paramagnetic at room temperature. Magnetic susceptibility values of the alloys showing paramagnetic magnetic properties were calculated as 11.5 × 10–6, 12.5 × 10–6, 9.15 × 10–6 and 6.15 × 10–6 emu.Oe−1.g−1, respectively. According to these results, the magnetic susceptibility value decreased with increasing Nd ratio.
AtıfScopus3WoS3OpenAlex3İncele - MakaleAçık Erişim2024Scopus SJRQ1Effect of White-Portland cement containing micro and nano silica on the mechanical and freeze-thaw properties of self compacting mortars
Etli, Serkan; Yılmaz, Tekin; Hansu, Osman
This study concentrated to investigate the influences of white-Portland cement (W-PC) containing silica fume (SF: micro-silica (µSi) and nano-silica (nSi)) as replacement (2–4 wt%) on mechanical (strength and durability), physical and microstructural behaviors of self-compacting mortars (SCMs) fabricated at 0.48–0.63 w/b ratios. In keeping with these purposes, besides of carrying out the workability (mini-slump flow: M−SF and V-funnel: V-F) experiments of SCMs, the mechanical and microstructural tests implemented were: unconfined compressive strength (UCS), flexural strength (FS), freeze–thaw (F-T) and scanning electron microscope (SEM) analysis. The outcomes displayed that, in comparison with the control, replacing W-PC by SF (particularly nSi) enhanced the UCS and FS, resisted against F-T durability by lowering the strength losses in UCS and FS. The ameliorated microstructure resulting in a reduction in the number and/or a narrowing in the size of micro-cracks and pores contributed to generate a more compact and consolidated SCM structure for the improving of strength and durability due of pore-filling effect and superior pozzolanic characteristics of µSi and especially nSi, this in turn reduced the permeability of SCM, which has a significant effect on the strength and durability behaviors of the SCM.
AtıfScopus16WoS16OpenAlex19İncele - MakaleAçık Erişim2024Scopus SJRQ1Effect of curing conditions on cement based self-compacting mortar produced with mortar waste aggregate
Akgül, Melek
Concrete and mortar wastes, which have a large volume and economic value among construction demolition wastes, are the most targeted demolition waste group to be recycled. An important area where construction demolition waste can be utilized is self-compacting mortar (SCM) systems. SCMs are innovative and economical systems designed to minimize the labor requirements that are difficult to meet in the production process. In this study, mortar waste aggregate (MWA) obtained by mechanical crushing and grinding was used in SCM elements by substituting different ratios (5-10-20-30-40 %) by mass to aggregate. In this way, it was aimed to evaluate both the sustainability of MWAs and the usability of MWAs in SCMs, which are considered as a new production technology. The fresh and hardened mortar tests performed in the study are presented comparatively. The physical (dry unit volume weight, porosity), durability (capillary water absorption) and mechanical properties (flexural tensile, compressive strength) of the hardened SCM elements are based on the determinations made at 3, 7 and 28 test days and according to different curing conditions (water curing, air curing and heat curing). In addition, X-ray Diffractometer (XRD) analysis was performed on specimens obtained from 0 %, 10 %, 20 % and 40 % MWA substituted specimens after heat curing (after 7 days water curing) and 28 days water curing. In the light of the data obtained, it is reported that SCM production with 10 % MWA substitution is feasible in terms of sustainability and engineering properties evaluated in this study.
AtıfScopus2WoS1OpenAlex2
İncele - MakaleYalnız künye2024Scopus SJRQ1Effects of Er2O3 contribution on microstructure and mechanical properties of high entropy and dual phase alloys
Taşgın, Yahya; Malkoç, Aziz; Kanca, M. Sait
The study aimed to look at the differences between a high entropy alloy and a dual phase high entropy alloy with high iron and Mn content. It also wanted to find out what happened when a small amount of the rare earth element erbium oxide (Er2O3) was added to these alloys, especially on the mechanical and microstructure of the alloy. The first step in this study was to get 99 % pure metal powders, which were then made by dividing the powders into 30 g of equal weight. The powders were mixed evenly and then pressed into 10-g blocks under 6 tons of pressure. They were then set up to be melted in an arc. Four of the eight samples that were melted in an arc under vacuum were treated with heat. The four different compositions were then turned into small metallographic samples for SEM, EDX, Mapping, XRD, and microhardness tests. The study's imaging and analysis processes were also carried out. After that, SEM images were taken at various magnifications (100X, 500X, 1000X, 2500X, and 5000X), and EDS and XRD analyses were done on different structures found in these images. These analyses were based on literature research about the clarity of the metallographic images in the alloy, which showed the study's metallographic differences. The samples were put through microhardness and wear tests to see which one was stronger and less worn. The dual phase high entropy alloy (A2) was stronger and less worn than the high entropy alloy (A1). Er2O3 had little effect on the alloys' mechanical properties or microstructure. The heat treatment that was done to the samples helped the metallographic structure. In terms of physics, it didn't change the hardness much, but it did make the material wear less quickly.
AtıfScopus1WoS1OpenAlex1İncele - MakaleYalnız künye2024Scopus SJRQ1Effect of boron on microstructure, thermal, and mechanical properties of Ni–B matrix diamond cutting tools
Islak, Serkan; Çelik, Ertuğrul; Houssain, Hasaneen; Danacı, Hacer Cemre
This study examines the impact of adding boron on the microstructural, thermal, and mechanical properties of Ni–B alloy matrix diamond cutting segments, which are created using the hot pressing process. Microstructure was investigated using SEM-EDS and XRD analysis. The high-temperature oxidation behavior of the samples was determined by thermogravimetric analysis. The hardness was quantified employing Vickers hardness testing, as well as, sample densities were derived based on Archimedes' principle. The wear resistance was evaluated using the reciprocating wear test method. A three-point bending test was used to examine how the diamond grains were retained inside the Ni–B matrix. The XRD investigations identified the formation of Ni, Ni3B, and Ni2B phases. The thermogravimetric analysis results showed that Ni–B alloys were exposed to oxidation at elevated temperatures as the B content increased, However, a hardness improvement was observed as the B content increased due to the formation of borides. Furthermore, the tribological investigation reveals that adding the B as reinforcement has a positive effect at a specific amount, where the optimal wear resistance and minimal friction coefficient were evident at 6% B contained sample.
AtıfScopus10WoS10OpenAlex10İncele - MakaleYalnız künye2023Scopus SJRQ3Mechanical property and structural-elemental analysis of marine bivalve mollusc shells: Cerastoderma edule, Chamelea gallina, Donax trunculus, Ruditapes decussatus
Kocabaş, Filiz Kutluyer; Kocabaş, Mehmet; Çanakçi, Aykut; Karabacak, A. Hasan
Mussels have great annual production in the world and their shells are discarded as a waste. Shells are calcium and carbon accumulators and, formed as a consequence of calcium carbonate biomineralisation. They can be used as bio‐based composite materials in different fields. Hence, assessment of the chemical compound content and microstructure of shells is important for the prospective utility. For these reasons, structure of Cerastoderma edule, Chamelea gallina, Donax trunculus, Ruditapes decussatus shells were analyzed with X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscope-Energy Dispersive Spectroscopy (SEM-EDS). In addition, microhardness was measured in shells. Our results indicated that shells have a flake like structure with irregular grains appearance morphologically at micrometric scale. The fractions of aragonite in particular shells were assessed. EDS analysis showed that Ca, C and O were major elements of C. edule, C. gallina, D. trunculus, R. decussatus in accordance with XRD data. The lowest microhardness (2.68±0.16 GPa) was in D. trunculus while the highest microhardness (4.28±0.32 GPa) was in C. edule.
AtıfScopus4İncele - MakaleAçık Erişim2022Scopus SJRQ1Corrosion behavior and crystal-microstructural analysis of non-equiatomic NiTi shape memory alloys
Kanca, M. Sait; Kök, Mediha; Qader, Ibrahim Nazem
NiTi shape memory alloys (Nitinol) are one of the most widely used families of smart materials that are used in smart systems and medical applications. The NiTi alloy with a composition of around 50 at. % Ni is very sensitive and just a small change in the components can make a big difference in the physical properties of the alloy. In this study, five non-equiatomic NiTi alloys with different compositions were fabricated with arc-melting in a controlled atmosphere. The crystal structure and morphology of the alloys were analyzed with x-ray diffraction (XRD) and scanning electron microscope (SEM), also the caloric properties of the alloys were investigated as a function of composition. Additionally, the samples were examined by the Tafel test to determine the corrosivity rate for one year in a simulated body fluid. The XRD and DSC results showed that only Ni44.56Ti55.44 at. % has martensite phase at room temperature, while the other alloys with higher Ni contents did not show martensitic phase transformation for the range of 230 K to more than 400 K. It was found that the alloys have corrosion rate around 10–4 mmpy which has comparably better than CuAlNi-based alloys. On the other hand, it was found that the corrosivity does not depend on the matrix phase of the NiTi alloy, but the composition ratio and other secondary phases play an important role.
AtıfScopus4WoS4OpenAlex6İncele - MakaleAçık Erişim2022Scopus SJRQ2Investigation of the Effects of Deformation Aging Applied to AA 7075 Aluminum Alloy on Mechanical and Metallographic Properties
Taşgın, Yahya; Ergin, Ramazan
Aging is quite important in improving the mechanical properties of aluminum alloys. One of the most widely used Al alloys is AA7075 aluminum alloy. Since AA7075 aluminum alloys contain aluminum-zinc-magnesium-copper, various aging processes have been applied to improve their mechanical qualities, and as a result, they have become commercially available. When this aluminum alloy series with increased strength is subjected to any thermal effect in industrial use, the loss of mechanical properties can be reduced by applying deformation aging. In this study, the effect of deformation aging on the mechanical properties of commercially available aluminum alloy has been determined and the relationship between mechanical properties and microstructure examined. Deformation aging was applied to 7075 Al alloy in our study by cooling in air, water and oil at temperatures of 120–180 °C for 2–24 hours. Structural differences were revealed by examining the effects of heat treatment on the mechanical properties and machinability properties of the alloy. As a result of the study, it was observed that metallographic precipitation occurred in the AA7075 Al alloy, and accordingly, intermetallic phases were formed. It is thought that various nanoscale fine precipitates occurring in the matrix of this alloy can also prevent dislocation movements. The study has positive effects on the mechanical properties of the material.
AtıfScopus9WoS6OpenAlex8İncele - MakaleYalnız künye2021Scopus SJRQ1Crack failure in hydrodynamically lubricated bearings: A case study hydraulic turbine
Taşgın, Yahya; Kahraman, Gökhan
This study investigates the trunnion crack of a 50 MW hydraulic turbine in the generator guide bearing. The crack area has been examined metallographically and the fixing method for the the trunnion crack has been explained. Result of the study shows that the reason for the formation of the bearing trunnion crack can be the thermal stresses that occur during the mounting of the bearing trunnion to the turbine shaft and the material fatigue that occurs during the operation of the hydraulic turbine.
AtıfScopus9WoS7OpenAlex9İncele - MakaleAçık Erişim2021Scopus SJRQ2Effects of Aging on Magnetic and Thermal Characteristics of NiMnCoSn Magnetic Shape Memory Alloys
Kök, Mediha; Aydoğdu, Kumruya; Kanca, M. Sait; Qader, Ibrahim Nazem; Öner, Ecem; Coşkun, Meltem
Heusler shape memory alloys are important for many applications due to their typical magnetic and shape memory behaviors. In this study, a Ni50Mn36Sn12Co2 (at.%) alloy was manufactured by arc-melting technique, then the ingot cooled to ambient temperature in the natural atmosphere. Three different temperatures, including 500 °C (773 K), 700 °C (973 K), and 900 °C (1173 K), was selected for aging the samples cut from the main ingot. The impact of aging on the crystalline; microstructure; caloric; and magnetic properties of the alloys were investigated through x-ray diffraction (XRD); scanning electron microscope; differential scanning calorimetric (DSC), differential thermal analysis, and thermal gravimetric (TG); and physical property measuring system was investigated, respectively. The aging in different temperatures led to the shift DSC curve, such that the martensitic phase transformation temperatures of the sample aged at 773 K increased, however, the transformation at 973 and 1173 K decreased compared to the as-casted alloy. The different phase transformation behavior showed that the alloy aged at 773 K has the maximum elastic energy, enthalpy and entropy change compared to the reset of samples, on the other hand, its crystallite sized obtained from XRD analysis comparably diminished. Besides, the TG analysis revealed that the mass gain almost occurs at a temperature above 773 K, therefore the magnetization of the alloys aged at 973 and 1173 K decreased due to a thin oxide layer formed on the surface of the alloys.
AtıfScopus5WoS5OpenAlex7İncele - MakaleYalnız künye2020Scopus SJRQ3Application of Local Hard Fillet Weld to Repair Damage Caused by Cavitation in Hydroelectric Power Plant
Kahraman, Gökhan; Taşgin, Yahya
Hydroelectric power plants come into prominence worldwide day by day due to their low operating and maintenance costs, environment friendly structure and their use as renewable energy sources. In order to obtain maximum energy from such an important energy source, it is necessary to reduce downtime due to failures. One of the most important failures of hydroelectric power plants is the damage caused to the turbine wheel by cavitation. In this study, a sample with the same material as the turbine wheels of the hydroelectric power plants is provided. The effects of the hard fillet weld on the turbine wheel, which we have applied locally to this material, have been investigated both metallographically and physically. As a result of the research, it is observed that the main material and hard fillet weld are mostly compatible. The damages of the turbine wheel of the hydroelectric power plant have been repaired by applying the same method to the turbine wheel damaged by the cavitation. After 10,000 h of operation, the turbine wheel is inspected again. As a result, it has been determined that the hard fillet weld applied to the turbine wheel surface is resistant to the harmful effects of cavitation.
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