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    Austempering Ce-La inoculated solution strengthened ferritic ductile cast irons
    (Redakcia Kovove Materialy, 2023) Yilmaz, Serdar Osman; Teker, Tanju; Demir, Demet
    The influence of austempering conditions on the microstructure, hardness, tensile strength, and impact toughness of Ce-La inoculated solution-strengthened ferritic ductile irons was an-alyzed. The austempering was performed at temperatures 280, 320, 420, 520, and 620 degrees C for periods of 1.5 and 2.5 h. Metallurgical characterization of the samples was determined using scanning electron microscopy, optical microscopy, X-ray diffraction, microhardness, impact, and tensile test. The fracture surfaces of the tensile samples were examined by scanning elec-tron microscopy. Austempering heat treatment significantly enhanced the mechanical charac-teristics of solution-strengthened ferritic ductile cast iron. This led to the birth of solution -strengthened Ce-La inoculated ferritic cast iron, a new spheroidal graphite cast iron family member with a unique microstructure in an ausferritic matrix. Samples austempered for low temperature exhibited higher impact toughness and tensile strength due to the nano-sized ausferrite phase. Austempering for high temperatures displayed higher elongation.
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    Improved Gx40CrNi25-20 grade austenitic stainless steel
    (Walter de Gruyter GmbH, 2024) Yilmaz, Serdar Osman; Teker, Tanju; Atik, Bahadır
    In this study, Ce inoculated GX40CrNi25-20 material was produced by casting. The materials were subjected to heat treatment by being exposed to two different temperatures (1100, 1150 °C) and two different cooling intensities. The effects of heat treatment on primary and secondary carbide concentration, distribution, and type were investigated by using optical microscope, scanning electron microscope, energy dispersive spectrometry, X-ray diffraction, and microhardness tests. The adhesive wear behavior of the materials was determined. After the homogenization heat treatment, the increased cooling intensity application decreased the hardness of the samples. After the homogenization heat treatment, the size of the primary carbides decreased and their distribution became homogeneous. Secondary carbides were dispersed into smaller and equiaxed formin the matrix. EGR inoculating reduced the precipitation of carbides and changed the shape of the precipitate to granule. © 2024 Walter de Gruyter GmbH. All rights reserved.
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    Mechanical properties of Sr inoculated A356 alloy by Taguchi-based gray relational analysis
    (Walter De Gruyter Gmbh, 2024) Yilmaz, Serdar Osman; Teker, Tanju; Dalmis, Ibrahim Savas; Bulus, Ercan
    In this study, Sr inoculated A356 alloy casted by sand-casting technique. Production parameters such as Sr concentration (wt.%), aging temperature (degrees C), aging time (h), and constant cooling rate were used. The effect of heat treatment on the microstructure and mechanical features of inoculated A356 materials was examined by using scanning electron microscopy, optical microscopy, and the Taguchi-based gray relational analysis method. The optimum production parameters for A356 alloy were determined as 0.03 Sr concentration, aging 300 degrees C temperature, and 3 h aging time. Multiple response optimization based on the interaction of these parameters provided a 30.15 % improvement in performance. Gray relational grade (GRG) experimental results showed that the most important parameter was Sr concentration, with a contribution of 76.51 %, according to the analysis by ANOVA statistical method.
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    Wear characteristics of cold tool steels for recycling plastic preprocessing
    (Walter de Gruyter GmbH, 2024) Dalmis, Ibrahim Savaş; Yilmaz, Serdar Osman; Teker, Tanju
    Eight type of commercial cold work tool steels were heat treated to achieve the equal hardness of 650-HV. Heat-treated samples were investigated by optical and scanning electron microscopy (SEM), microhardness, and X-ray diffraction (XRD) to identify microstructural features and phases. The samples were examined in three distinct wear modes: adhesion, two-body wear using pin wear on SiC, and recycling plastic cutting machine, respectively. The wear surfaces of samples were analyzed by 3D scanning technology. The microstructure of steels determined their wear characteristics. For low sliding and higher cutting speeds, the order of adhesive wear performance of the steels was reversed due to the stress occurring in the cutting line. The wear rate of all samples was commensurate with load. In the recycling plastic cutting process, the sample with the minimum and homogeneously dispersed carbides exhibited the best wear performance. Tempering the S3 sample prevented crack formation and improved fracture toughness. © 2024 Walter de Gruyter GmbH, Berlin/Boston.