WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Microstructure-Based Prediction of Mechanical Properties of Austempered Ductile Iron Using Multiple Linear Regression Analysis(Springer int Publ Ag, 2025) Yalcin, M. Alp; Davut, KemalMultiple linear regression analysis (MLRA) was used to predict the mechanical properties of austempered ductile iron (ADI) including yield and tensile strength, uniform elongation, hardening exponent, as well as fracture energy by building a model that uses characteristic features of microstructural constituents as input parameters. The complex multi-scale microstructure of ADI, which is composed of spherical graphite particles over 10 mu m diameter; and an ausferritic matrix with sub-micron sized features, makes it ideal for prediction of mechanical properties. For that purpose, low alloyed ductile iron samples austempered between 300 and 400 degrees C for 45-180 min were tensile tested, and also multi-scale microstructural characterization were carried out using optical microscope, SEM, and EBSD technique. Moreover, a sensitivity analysis was performed to determine which microstructural parameter(s) each mechanical property is most sensitive to. The results show that tensile and yield strength are most sensitive to size and morphology of matrix phases. Moreover, the size and aspect ratio of acicular ferrite correlate well with those of high-carbon austenite; since both form during transformation of parent austenite into ausferrite during austempering treatment. Equiaxed parent austenite grains transform into ausferrite with acicular morphology during the austempering treatment; and presence of equiaxed austenite grains in the austempered samples indicates untransformed regions during austempering treatment. Ductility was found to be more sensitive to nodularity of graphite particles, and this sensitivity was attributed to the size difference between graphite particles and grain size of matrix phases.Article Effects of Industrial and Domestic Wastewater Treatment Plants on Microplastic Pollution in an Urban River in Türkiye(Springer int Publ Ag, 2025) Baycan, Neval; Alyuruk, Nefise; Kazanci, Yigithan; Alpergun, Cumana; Kara, Nursena; Tasdelen, Ozge; Gunduz, OrhanMicroplastic (MP) contamination in inland aquatic systems is a growing environmental concern due to its persistence and potential ecological impacts. This study provides a comprehensive assessment of the occurrence, composition, and seasonal dynamics of MPs in two urban rivers-Nif Creek and Gediz River-in western T & uuml;rkiye, which receive treated and untreated effluents from domestic and industrial wastewater treatment plants (WWTPs). A total of 20 river water and 3 sediment sampling stations were monitored across four seasons. MP concentrations ranged from 7 to 146 particles/L in water and from 9,867 to 136,177 particles/kg in sediments, with the highest abundances observed near WWTP outfalls and urban infrastructure. Polypropylene was the dominant polymer in water (59.1%) and WWTP effluents (44.4%), while polyethylene was most prevalent in sediments (60.2%). MPs were primarily within the 0.1-0.5 mm size range and were predominantly transparent in colour. Statistical analyses indicated significant positive correlations between MP abundance and key water quality parameters, including chemical oxygen demand, total suspended solids, and selected heavy metals (e.g., Zn, Cd, Ni). The polymeric composition of MPs reflected both urban and industrial sources, with variations in polymer profiles linked to spatial and seasonal factors. Compared to values reported in European freshwater systems, MP levels in the studied rivers were considerably higher, underscoring the need for improved wastewater management and targeted monitoring efforts in urban river basins.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.