Sürdürülebilir Kalkınma Amaçları

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• MakaleAçık Erişim2026Scopus SJRQ2/r/munzur/1340
  Effects of Magnetic Abrasive Finishing Process Parameters on the Inner Surface Machining of AISI 304 Austenitic Stainless Steel Pipes

  Sarıçiçek, İzel; Çaydaş, Alparslan Ulaş; Cihangir, Salih; Say, Yakup

  In this study, the effects of SiC abrasive ratio, size of magnetic Fe particles and the machining time parameters on the surface roughness, material removal rate, roundness of the holes and corrosion resistance in magnetic abrasive inner surface finishing (MAF) of the AISI 304 austenitic stainless steel pipes were experimentally investigated. A Taguchi L9 orthogonal array was used for the experiments. The surface roughness and the characteristics of the machined surfaces were examined by using the3D surface topography method. The characteristics of the abrasive and magnetic powders before and after machining operations were investigated under scanning electron microscope (SEM) and x-ray diffraction analysis (XRD) techniques. The electrochemical corrosion measurements were performed in 3.5 wt.% NaCl solutions in a typical three-electrode electrochemical cell. An analysis of variance (ANOVA) method was also applied to the study in order to determine the statistical effects of each factor on the measured responses. Consequently, AISI 304 samples machined with MAF technique revealed better results for corrosion performance, surface quality, material removal rate and the hole dimensional tolerances.

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• MakaleYalnız künye2026Scopus SJRQ2/r/munzur/1191
  Influence 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.

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• MakaleAçık Erişim2026Scopus SJRQ2/r/munzur/1068
  Investigation 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.

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• MakaleYalnız künye2026Scopus SJRQ2/r/munzur/800
  Oxide 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.

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• MakaleYalnız künye2025Scopus SJRQ2/r/munzur/1375
  Investigation of Mechanical Properties of Jute and Tea Waste-Reinforced Epoxy Composite Material Produced by Vacuum Assisted Resin Infusion Molding

  Dogan, Akar; Mahmat, Aybars; Agar, Salih

  Recently, the production of materials obtained from plant sources has been increasing due to their environmentally friendly and sustainable sources. Natural fibers and waste materials offer a remarkable alternative in composite production due to their biodegradability, low cost and renewability. In this study, composite materials were produced using hybrid Jute and industrial tea waste-reinforced epoxy materials by vacuum assisted resin infusion molding. In this context, the reason for using natural and industrial resources such as jute fiber and tea waste is to contribute to both the improvement of mechanical properties and the reduction of environmental impacts. It was observed that tensile and flexural strength decreased as the amount of tea waste increased. Conversely, the energy absorbed during the quasi-static punch shear and Charpy impact tests increased, unlike the tensile and flexural strength. Approximately 50% decrease was observed in the tensile strength of the 60% tea waste reinforced material compared to the pure jute composite material. In Charpy impact and quasi-static punch shear tests, a 5% increase in the energy absorbed in the 60% tea waste reinforced composite materials was obtained.

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• MakaleYalnız künye2025Scopus SJRQ2/r/munzur/1314
  Phase Stability, Structural Properties, Electronegativity, Mechanical Properties, and Neutron and Gamma-Ray Attenuation Properties of Cantor High Entropy Alloys for Advanced Nuclear Applications

  Tekin, H.O.; Güler, Ömer; Özkul, İskender; AlMisned, Ghada; Baykal, Duygu Sen; Alkarrani, Hessa; Kilic, G.; Mesbahi, A.

  High Entropy Alloys (HEAs) hold considerable potential for sophisticated nuclear applications, offering a vast spectrum of compositional tuning to enhance mechanical properties at high temperatures, as well as to increase resistance to radiation and corrosion. This study explores the suitability of Cantor HEAs, specifically the CoCrFeMnNi matrix enriched with elements such as Zr, Nb, Mo, Hf, Ta, and W, for nuclear applications. These elements were selected for their high atomic numbers and neutron capture cross-sections, vital for enhancing gamma-ray and neutron shielding properties. Utilizing advanced computational and theoretical methods, the elastic modulus of these alloys was theoretically estimated while their radiation attenuation capabilities were evaluated through different Monte Carlo simulation codes. CoCrFeMnNiW demonstrated the highest elastic modulus (340.9 GPa), indicating significant mechanical robustness. The addition of W resulted in superior gamma-ray attenuation, with the lowest gamma-ray transmission factors and highest neutron shielding effectiveness among the studied alloys. The calculated mass attenuation coefficients and effective removal cross-sections values demonstrate the potential of these HEAs to provide effective radiation shielding. Our results showed a clear correlation between the elastic modulus and radiation attenuation properties, suggesting that mechanical stiffness does not compromise shielding capabilities. The comprehensive analysis of thermodynamic and structural parameters, including entropy of mixing, mixing enthalpy, and Valence Electron Concentration (VEC), provided essential insights into phase stability and microstructural characteristics. It can be concluded that CoCrFeMnNiW and its related Cantor HEAs as promising materials for advancing nuclear technology, offering a new horizon for safer and more efficient nuclear systems.

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• MakaleYalnız künye2024Scopus SJRQ2/r/munzur/2128
  Recycling Ti1.0Nb0.3Ta0.07Zr0.05 Conventional Alloys: Production of Non-equimolar TiZrCrNb0.3Ta0.07 Medium Entropy Alloys with the Addition of Cr for Improved In Vitro Corrosion Resistance

  Guler, Omer; Say, Yakup; Dikici, Burak; Ozkul, Iskender; Niinomi, Mitsuo

  A non-equimolar TiZrCrNb0.3Ta0.07 medium entropy alloy (MEA) was successfully designed as theoretical and produced by arc-melting method from Ti1.0Nb0.3Ta0.07Zr0.05 (TNTZ) scraps for possible usage in biomedical applications in this study. The main aim of this study is to find an alternative way to recycle with a reduced carbon footprint the available TNTZ conventional alloy and convert it to a value-added product during this recycling such as medium entropy alloys (MEAs) via using less energy. To examine the microstructural changes induced by the annealing process, scanning electron microscopy was employed. The chemical composition of the HEAs was assessed using energy-dispersive spectroscopy and x-ray photoelectron spectroscopy. Additionally, x-ray diffraction analysis was used to determine the crystallographic structure and phase composition of HEAs. Furthermore, in order to evaluate the electrochemical corrosion performance of the alloys, comprehensive in vitro corrosion tests were conducted in a simulated body fluid solution, specifically Hanks's Balanced Salt Solution. Some elemental segregation has been observed after the annealing process. A big migration of Zr and Cr elements was observed in the samples from the interdendritic region to the dendritic area during the annealing process. This segregation resulted in approximately 1.4 times increase in the hardness of the MEA. The electrochemical corrosion results showed that the in vitro resistance of the MEAs was higher than that of its conventional scraps.

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• MakaleYalnız künye2024Scopus SJRQ2/r/munzur/2041
  Dynamic Analysis and Metallographic Examination of Linings with Different Composite Contents used in the Brakes of a Hydraulic Turbine

  Işık, Erdem; Kahraman, Gökhan

  The main aim of this study was to find ways to increase the performance and life of generator brake linings, which can lead to cost reduction and adequate downtime periods for hydroelectric power plants. First, the dynamic analysis of the linings used in hydraulic turbines was realized and their reactions were examined under different operating conditions. Second, two types of brake linings with different composite components produced in the market were examined metallographically and tested to determine both the stopping performance and durability time of the turbine-generator unit for a sufficient period of time in the vertical 150-megawatt Francis turbine with approximately 500 tons of rotary weight. As a result of these experiments, the lining with the boron component led to much better results than the other brake linings. It has been determined that the boron-containing lining makes 100 stops more than the other lining and stops 20 s earlier in one stop. Therefore, the use of a composite lining with boron content in the braking systems of hydroelectric power plants significantly reduces maintenance incidents and operation costs as it prolongs brake replacement periods in these plants. Graphical Abstract: (Figure presented.)

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• MakaleYalnız künye2024Scopus SJRQ2/r/munzur/1800
  A Study on Comprehensive Production Parameters of Boron Nitride 2D Nanomaterial

  Güler, Seval Hale; Safa, Hasan

  In this study, BNNSs were synthesized via liquid-phase exfoliation method. Hexagonal boron nitride powders were used as the starting material. The production of boron nitride nanosheets was optimized. For this purpose, different sonication parameters and the effects of different solvents have been investigated. Different sonication power and time parameters of the homogenizer (Sonics Vibra-cell VCX, 750 W) used as the sonication parameter have been changed. In this stage, they were subjected to sonication process first for 1-1.5-2 hours at 25% sonication power, 1-1.5-2-4 hours at 50% sonication power, and 1-1.5-2-4-6-8 hours at 75% sonication power. As a result of particle size analysis, time/sonication power parameters were determined as 2 h-75%, 2 h-50%, 4 h-75%, 2 h-50%. The obtained samples were sedimented with centrifuge process, washed with distilled water to remove solvent, and dried. Different solvents were compared in the best power–time relationship. These solvents are dimethylformamide (DMF), isopropyl alcohol, N-methyl pyrrolidone, ethylene glycol. The best results were obtained in DMF. The synthesized BNNS samples were subjected to particle size (Malvern), scanning electron microscope (Zeiss, Gemini Supra 55), transmission electron microscope (Jeol Jem-1011), Fourier transform infrared spectroscopy (Thermo Scientific Nicolet™ iS™ 5), Raman (WITech alpha 300R), x-ray photoelectron spectroscopy (Specs-Flex), and x-ray diffraction analysis (PANalytical Empyrean).

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• MakaleYalnız künye2024Scopus SJRQ2/r/munzur/1637
  Production of CoCrFeNi(Al/Ti) High-Entropy Alloys by Mechanical Alloying: Optimization of Milling Time and Comparison of Corrosion Susceptibilities

  Say, Yakup; Dikici, Burak; Kaseem, Mosab; Özkul, İskender; Güler, Ömer

  CoCrFeNi alloy is the most well-known four-component equiatomic alloy. In addition, it has a low-cost composition among HEAs. Four-component alloys are considered semi-HEAs. Therefore, a five-component HEA design was made by adding another metal to the main composition of CoCrFeNi. As the fifth metal, two metals such as Al and Ti, which are relatively low in cost and have the potential to improve properties, were chosen. For this purpose, in this study, the effect of Al and Ti on CoCrFeNi main alloy was investigated by producing three different samples as CoCrFeNi, CoCrFeNiAl, and CoCrFeNiTi. The alloys with three different compositions (used three different samples) were successfully produced by the mechanical alloying method. Although Al and Ti have the possibility of intermetallic with other metals in the alloy, such a formation was not observed during mechanical alloying, and it was observed that all metals were homogeneously distributed in the alloy. The microhardness results indicated that CoCrFeNiAl and CoCrFeNiTi samples had similar hardness values. While the hardness of the CoCrFeNi sample was 136 HV, the hardness of the CoCrFeNiAl sample was 262 HV. However, the hardness of the CoCrFeNiTi sample decreased significantly. The hardness of the CoCrFeNiTi sample was measured as 269 HV. It was observed that the addition of Ti and Al to the base alloy was increased a significant change in hardness. It has been observed that Ti supplementation has a more positive effect on improving corrosion properties. It is seen that the corrosion potentials shift toward more negative potentials with the addition of Al and Ti to the CoCrFeNi (−194 mV) alloy (−306 and −224 mV for CoCrFeNiAl and CoCrFeNiTi, respectively). When the surface morphologies of the alloys are compared after corrosion; the damage to the alloy surfaces increases due to the negative Ecorr value in CoCrFeNiAl and CoCrFeNiTi alloys compared to the master alloy. However, the high corrosion current density (12.69 µA/cm2) in the CoCrFeNiTi sample caused much more damage to this alloy. Graphical Abstract: (Figure presented.)

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