Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
8 results
Search Results
Now showing 1 - 8 of 8
Article Citation - WoS: 3Citation - Scopus: 3Influence of Oscillating Fiber Laser Welding Process Parameters on the Fatigue Response and Mechanical Performance of Butt-Jointed Twip980 Steels(Walter de Gruyter Gmbh, 2025) Cavusoglu, Oktay; Aydin, Hakan; Eroglu, Mehmet; Davut, KemalIn this study, the effect of laser power, welding speed, linear heat inputs on the mechanical performance of TWIP980 steels joined by oscillating fiber laser welding in butt welding configuration was investigated. Oscillating fiber laser welding were changed: laser power from 1.2 to 1.6 kW, welding speed from 20 to 30 mm s-1, linear heat input from 40 to 80 J mm-1. The tensile, hardness and fatigue tests were carried out to determine mechanical performance. A significant improvement in weld penetration, fatigue performance and mechanical properties was detected at linear heat inputs above 53.33 J mm-1. The best mechanical properties were obtained at 1.6 kW laser power and 25 mm s-1 welding speed. The study reveals that linear heat inputs, laser power, and welding speed have significant effects on mechanical performance and weld geometry. Furthermore, the results demonstrate that oscillating fiber laser welding enables good weldability even at low laser power.Article Citation - WoS: 6Citation - Scopus: 10Influence of the Heat Treatment on the Microstructure, Mechanical and High-Temperature Oxidation Behavior of Hastelloy X Alloy Fabricated Via Laser Powder Bed Fusion(Elsevier Science Sa, 2025) Ozer, Seren; Yalcin, Mustafa Alp; Bilgin, Gueney Mert; Davut, Kemal; Esen, Ziya; Dericioglu, Arcan F.The effect of building direction and heat treatment on the microstructure, mechanical properties, and high- temperature oxidation behavior of Hastelloy X (HX) alloy fabricated by the laser powder bed fusion (L-PBF) method was studied. Electron backscatter diffraction analyses revealed that the development of textured columnar grains with varying average grain sizes, boundary fractions, and dislocation densities induced the mechanical anisotropy observed in both horizontally and vertically fabricated samples. The yield strength (YS) values of the horizontally and vertically as-fabricated samples were determined as 605.7 +/- 15.9 MPa and 552.3 +/- 8.5 MPa, respectively. The post-processing heat treatment increased the ductility remarkably and reduced YS value down to similar to 445 MPa for all samples by the elimination of microstructural anisotropy and increased grain size subsequent to recrystallization. Oxidation tests conducted at 900 degrees C up to 100 h on as- fabricated samples exhibited severe intergranular oxidation, which was accompanied by the formation of large voids and microcracks as well as spallation of the oxide layer. In contrast, the heat-treatment improved the oxidation resistance of the alloy possibly due to the formation of uniform and dense Cr2O3 layer on the substrate surface.Article Citation - WoS: 2Citation - Scopus: 2The Spheroidization Behavior of Low Alloy White Cast Iron and Its Effect on Impact Toughness and Wear Resistance(Elsevier Science Sa, 2025) Camkerten, Ruziye; Davut, Kemal; Yilmaz, Tolga; Nalcaci, Burak; Erdogan, MehmetThe effect of spheroidization on impact toughness and wear resistance, together with the spheroidization kinetics of a low alloy white cast iron (LAWCI) have been studied. Spheroidization process was carried out using two different routes; intercritical annealing and subcritical annealing both of which were followed by furnace cooling to room temperature. Both routes involve a process window, which is determined by holding time and temperature. For the intercritical annealing the spheroidization window is significantly shorter (0.5-3 h) than the conventional subcritical spheroidization (6 - 12 h); and that process window narrows with increasing intercritical annealing temperature. The intercritical spheroidization involves 3 distinct stages; (i) partial, followed by (ii) fully spheroidization of lamellar pearlitic matrix by divorced eutectoid transformation (DET); and (iii) partially spheroidization by pearlitic structure formation in previous fully spheroidized region. The end of third stage produces almost fully pearlitic matrix, which is coarser than the as-cast condition. In case of subcritical spheroidization, the process window opens after about 6 hours and the size of spherical carbides gets larger with time. The as-cast LAWCI having a microstructure composed of eutectic carbide network and pearlite matrix exhibits and impact toughness of 4.6 J. Spheroidization process not only changes the lamellar pearlitic structure into spheroidized carbides but also slightly reduces the amount of eutectic carbides. Those microstructural changes greatly improve the impact toughness of LAWCI up to 11.8 J; whereas some decrease in the wear resistance. For spheroidized LAWCI, mean diameter of carbides (D), interparticle spacing of carbides (s), and number of carbides per area (n) seems to be important microstructural variations to determine the impact toughness and wear properties. Taking properties of the current material into consideration, spheroidized white cast irons may be a viable alternative material for industrial applications, offering a trade-off between wear resistance and toughness.Article Citation - WoS: 1Citation - Scopus: 1Chemical Composition Optimization and Isothermal Transformation of Δ-Transformation Plasticity Steel for the Third-Generation Advanced High-Strength Steel Grade(Wiley-v C H verlag Gmbh, 2024) Okur, Onur; Davut, Kemal; Palumbo, Gianfranco; Nalcaci, Burak; Guglielmi, Pasquale; Yalcin, Mustafa Alp; Erdogan, MehmetA new low-manganese transformation-induced plasticity steel is designed with optimized nickel content to achieve superior strength and ductility while minimizing the use of expensive nickel. The steel is optimized using JMatPro software, then cast, and hot rolled. To assess the effect of intercritical annealing on austenite (martensite at room temperature) volume fraction and carbon content, hot-rolled steel samples quenched from different annealing temperatures (680-1100 degrees C) are used. Additionally, hot-rolled steel coupons are intercritically annealed at about 50% austenite formation temperature (740 degrees C) and then subjected to isothermal treatments at 300-425 degrees C for varying times (10-90 min). After optimizing these treatments to maximize retained austenite (RA), tensile specimens are heat-treated first at 740 degrees C and then isothermally at 325 degrees C. Thermodynamic calculations suggest that aluminum combined with silicon may lead to the delta ferrite formation, and even minimal nickel content can stabilize a considerable amount of austenite. In the experimental studies, it is shown that lower-temperature bainitic holding enhances austenite stability by enriching the carbon content. Optimized two-stage heat treatments yield up to 25.8% RA, with a tensile strength of 867.2 MPa and elongation of 40.6%, achieving a strength-elongation product of 35.2 GPax%, surpassing the third-generation advanced high-strength steel grades minimum requirement of 30 GPax%.Article Citation - WoS: 1Citation - Scopus: 1Effect of Mn Concentration on Mechanical Properties of A356 Aluminum Alloy Wheels Produced by Low-Pressure Die Casting(Springer int Publ Ag, 2024) Kaya, A. Yigit; Davut, Kemal; Gokelma, MertolSecondary aluminum alloys in automotive industry have been rising in last decades; however, the iron content is still a concern whether recycled or high iron containing aluminum alloys can fulfill the mechanical requirements. As the proportion of recycled scrap increases in aluminum alloy components, the mixing and accumulation of impurities become significant issues. In this study, manganese was used to counteract the detrimental effects of iron. Accordingly, A356 alloy automobile wheels containing 0.002 wt%, 0.040 wt%, 0.069 wt%, and 0.14 wt% Mn were cast using the low-pressure die casting method, followed by T6 heat treatment. Optical microscope (OM) examinations were performed to observe intermetallics. Additionally, the mechanical properties of the produced wheels were evaluated through hardness measurements, tensile, and Charpy impact tests. After the Charpy impact test, fractured surfaces were examined using scanning electron microscopy (SEM). Micrographs from SEM and OM were quantified using digital image processing. To interpret this extensive dataset, a statistical model was developed using microstructural data as input through multiple linear regression analysis and analysis of variance. The results were discussed together with the sensitivity analysis. A weak negative linear correlation between Mn concentration and mechanical properties was found, indicating that Mn addition is not the primary factor for the observed decrease in mechanical properties. Elongation and yield strength were significantly influenced by both aspect ratio and particles/mm2, with greater sensitivity to particles/mm2. Additionally, impact energy was strongly affected by aspect ratio of particles (intermetallics and eutectic Si) and their concentration per unit area.Article Citation - WoS: 5Citation - Scopus: 4Influence of Partitioning Treatment on Microstructure and Mechanical Properties of an Alloyed Ductile Iron Austempered at Different Temperatures(Walter de Gruyter GmbH, 2023) Neite, Maximilian; Münstermann, Sebastian; Nalçacı, Burak; Davut, Kemal; Erdoğan, MehmetThe present study was conducted to uncover effects of partitioning treatment on Cu-Ni-Mo alloyed ductile iron (DI) austempered at different temperatures. For this purpose, the DI samples, produced via sand casting, were austenitized at 900 °C for 60 min, followed by austempering at the temperatures of 275-325-375 °C for 120 min and afterwards a partitioning treatment was applied at 200 °C for 15 min. In the characterization studies, dilatometer, image analysis, JMat-Pro, mechanical tests, XRD, optical microscope, and scanning electron microscope (SEM) equipped with EBSD detector were utilized. Characterization studies showed that the effects of partitioning treatment were directly correlated with austempering temperature and high carbon austenite volume fraction changed in the range of 19.48-35.45%. That redistribution of carbon (C) between bainitic ferrite and high carbon austenite occurred, in turn, the carbon content of high carbon austenite increased with the partitioning treatment irrespective of austempering temperature were uncovered. Furthermore, the partitioning treatment considerably changed the grain morphologies of both high carbon austenite and banitic ferrite. As a consequence of these microstructural differences, the highest tensile strength of 1489.2 MPa was established in the sample austempered at 275 °C and partitioned at 200 °C, whereas the highest ductility of 5.61% acquired at the austempering temperature of 375 °C. © 2023 Walter de Gruyter GmbH, Berlin/Boston.Article Citation - WoS: 29Citation - Scopus: 31Effect of Heat Input on Haz Softening in Fiber Laser Welding of 22mnb5 Steel(Elsevier, 2023) Tuncel, Oğuz; Aydın, Hakan; Davut, KemalThis study investigates the effects of heat input on the heat-affected zone (HAZ) softening in fiber laser welding of quenched 1.1 mm thick 22MnB5 steel. Laser power (1500-2500 W) and welding speed (40-120 mm/s) parameters are considered as the input process variables. Depending on the input parameters, the applied heat input varied between 12.5 and 62.5 J/mm. The results indicate that a minimum heat input of 50 J/mm is required for full weld penetration. Microhardness findings revealed that the drop in hardness in the HAZ region relative to the base material (BM) reached 39% due to grain coarsening caused by an increase in heat input under the welding conditions. Grain coarsening (prior austenite grains) is also detected in SEM analysis. In addition, grain coarsening at high heat input was also determined quantitatively in EBSD analyses. The proportion of 8.91 mu m grain size in the sample with high heat input is 4.2%, while it is 1.2% in the sample with low heat input. When the heat input increased from 12.5 to 62.5 J/mm, the width of the softened zone with the lowest hardnesses in the HAZ grew from 0.2 mm to 2.2 mm.Article Citation - WoS: 3Citation - Scopus: 3Nondestructive Microstructural Characterization of Austempered Ductile Iron(Walter de Gruyter GmbH, 2023) Tüzün, Mert Yağız; Yalçın, Mustafa Alp; Davut, Kemal; Kılıçlı, VolkanAustempered ductile iron (ADI) has been preferred in a wide range of applications due its unique combination of high strength, good ductility, wear resistance and fracture toughness together with lower cost and lower density compared to steels. Magnetic Barkhausen noise (MBN) measurement offers a better alternative to traditional characterization techniques by being fast and non-destructive. A simple linear regression using only one single independent variable cannot correlate the MBN with the microstructure of ADI, since its microstructure is multi component. Multiple linear regression analysis (MLRA) was used to build a model that uses the characteristic features of microstructural constituents as input parameters to predict the MBN. For that purpose, Cu-Ni-Mo alloyed ductile iron samples austempered between 325 and 400 degrees C and for 45-180 min duration were used. The results show that MBN is most sensitive to the size and shape of acicular ferrite and retained austenite. Moreover, MBN is almost insensitive to the size, morphology and volume fraction of graphite particles. This indicates that retained austenite pins the domain walls more effectively than the graphite particles. Considering the results MLRA, MBN technique can be used to characterize the ausferritic microstructure of ADI.