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    Determination of the Effective Fused Deposition Modeling Process Parameters on the Mechanical Properties of Carbon Fiber-Reinforced Polypropylene Parts
    (Amer Soc Testing Materials, 2024) Eryildiz, Meltem; Kosa, Ergin; Yavuzer, Bekir; Akgun, Ismail Cem
    Additive manufacturing is gaining popularity for producing components in industries such as automotive, aerospace, and medicine due to its potential to minimize material waste. Because the strength of the 3-D-printed part is so important, it's crucial to do research and optimize process parameters to make the printed parts as strong as possible. This work focuses on the experimental investigation and discussion of the tensile and impact strength of parts made from carbon fiber-reinforced polypropylene (PP-CF) using the fused deposition modeling (FDM) technique. Various process parameters, including infill pattern, infill density, layer thickness, and build orientation, are examined on three different levels to determine their influence on the tensile and impact strength of the printed part. The outcomes of the analysis of variance (ANOVA) analysis reveal that infill density primarily affects impact strength, whereas layer thickness significantly influences tensile strength. The optimal combination of parameters leading to the maximum tensile and impact strength consists of a grid infill pattern, 60 % infill density, 0.36-mm layer thickness, and a 45 degrees build orientation. Furthermore, fracture surface analysis is consistent with mechanical test results.
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    Effect of Alloying Time and Heat Treatment on Microstructure and Tribological Properties of Mechanical Alloyed Cu-Al-Ni Shape Memory Alloy
    (Springer, 2023) Yavuzer, Bekir; Bicakci, Unal; Simsek, Dogan; Ozyurek, Dursun
    In this study, the effects of milling time and heat treatment on microstructure and wear behavior of Cu-Al-Ni shape memory alloys produced by the mechanical alloying method were investigated. Cu-Al-Ni shape memory alloys were produced by mechanical alloying in four different durations (2.5, 5, 7.5 and 10 h) in a planetary-type mill. The produced Cu-Al-Ni shape memory alloys were characterized by microstructure (SEM + EDS), x-ray diffraction, thermal analysis (TG/DTA-DSC), and hardness, density, and dust size measurements. In the wear tests, three different loads (10, 20, and 30 N), five different sliding distances (400, 800, 1200, 1600, and 2000 m) and a sliding speed of 1 ms-1 were used. As a result of the studies, it was observed that the powder size decreased with the increase in MA time. It was observed that the density of heat-treated shape memory alloys decreased compared only to sintered alloys. According to the wear test, the lowest wear rate was obtained in Cu-Al-Ni shape memory alloys exposed to mechanical alloying for 7.5 h, with the highest hardness value. In addition, it was observed that the wear rates decreased in heat-treated Cu-Al-Ni shape memory alloys as the sliding distance increased.
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    Effect of Compression Time on Microstructure and Hardness of A356 Fabricated via Thixoforming
    (Kırıkkale Üniversitesi, 2021) Yavuzer, Bekir; Özyürek, Dursun
    This study investigates the effect of compression time and milling on microstructure and hardness of A356 alloy produced by thixoforming, which is one of the semi-solid forming methods. As a result of the microstructure studies, it was determined that there was an increase in the globalization amount of the grains and a decrease in the grain sizes depending on the compression period. The highest globularization rate was measured in the sample, which did not milled and had 2 minutes compression time in the thixoforming process. As a result of the hardness measurements taken from different positions of the samples, it was observed that the hardness values of the samples decreased from the outer surface. The highest hardness value was obtained from the samples produced by compressing for 2 minutes and not milled. In addition, EDS analysis results showed that there is more silicon in the grain boundaries than in the grain.
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    The Effect of Ni Addition on Microstructure and Mechanical Properties of Cast A356 Alloy Modified With Sr
    (Redakcia Kovove Materialy, 2021) Yavuzer, Bekir; .;, ve diğer
    In this study, casting A356 alloy was pre-alloyed with Ni, and the modification process with Sr was applied by the casting method. The role of Ni on the microstructural and mechanical properties of the produced A356-Ni alloys was investigated. The produced alloys were naturally aged at room temperature for 24 h and artificially aged at 170 degrees C for 10 h. Optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffractometer were used in microstructure studies of the A356-Ni alloys. Tensile tests and hardness measurements were carried out to determine mechanical properties. Statistical analysis of Weibull distribution on the tensile test results revealed that the characteristic ultimate tensile strength increased due to increasing the amount of alloying elements, while the characteristic percentage elongation is decreased. This was because Al-Si-Fe intermetallic decomposition and Al-Si-Fe-Ni intermetallics were formed, primarily, 0.5 and 1.0 % Ni addition. It was also determined that the Al-Si-Fe-Ni intermetallics with a morphology non-sharp corners formed more homogeneous in the microstructure. But in the A356 alloys with the addition of 1.5 % Ni, Al-Si-Fe-Ni intermetallics are formed in coarser morphology. In A356 alloys, aluminium dendrites, Al-Si eutectic between dendrites, Mg2Si precipitates are formed in the structure by ageing. Depending on the amount of Ni added to the A356 alloy, the tensile strength of the alloys containing 0.5 and 1.0 % Ni is increased.
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    Effect of niobium addition on the microstructure and wear properties of mechanical alloyed Cu-Al-Ni shape memory alloy
    (Walter De Gruyter Gmbh, 2024) Yavuzer, Bekir; Turkmen, Mustafa; Bicakci, Unal; Ozyurek, Dursun
    In this study, the influence of the addition of Nb in varying amounts (0.5, 1, 1.5, and 2 wt.%) to Cu-14Al-4Ni shape memory alloy on the microstructure and wear behavior of the alloy was investigated. Cu-Al-Ni-xNb alloys were produced from elemental powders using the mechanical alloying (MA) method. The microstructures of the produced samples were examined using SEM + EDS and XRD, and density and hardness measurements were performed. For the wear tests of Cu-14Al-4Ni and alloys containing different amounts of Nb, a pin-on-disk type wear testing device was used with three different loads (10 N, 20 N, and 30 N) and five different sliding distances (400 m, 800 m, 1,200 m, 1,600 m, and 2000 m). As a result of the conducted research, it was determined that an increase in the Nb content resulted in a decrease in the average grain size and a more homogeneous grain size distribution. The highest hardness and density values were measured in the alloy with 2 wt.% Nb addition. In the wear tests, it was observed that the friction coefficients decreased with increasing load, and the lowest wear rate was achieved in the alloy with 2 wt.% Nb addition.
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    The Effects of Small Amounts of Niobium Addition to Mechanical Alloyed AISI 304 Stainless Steel on the Microstructural and Tribological Properties
    (Springer India, 2023) Yavuzer, Bekir; Ozyurek, Dursun
    In this study, the effects of different amounts (max 1%) of niobium added to mechanical alloyed AISI 304 austenitic stainless steel on the hardness, density, microstructure, and wear behavior were investigated. After the AISI 304/Nb alloy powders were cold pressed, they were sintered in vacuum environment (10(-6) mbar) at 1300 degrees C. The produced AISI 304/Nb samples were characterized by scanning electron microscopy, X-ray diffraction, and hardness and density measurements. Wear tests were performed under dry friction at room temperature using a pin-on-disk wear device. Result of the study showed that the addition of niobium up to 0.4% increased the hardness of the alloy and improved wear behavior while greater ratios reduced the hardness of the alloy and negatively affected wear behavior. Oxidation occurred on the worn surface and lines were formed in the sliding direction. In addition, as the hardness values of the alloy increased, weight loss decreased.
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    Enhancing 3D-Printed PP-CF parts: A novel resin-filling technique for mechanical property optimization
    (Sage Publications Ltd, 2025) Eryildiz, Meltem; Kosa, Ergin; Akgun, Ismail Cem; Yavuzer, Bekir
    This study investigates a novel post-processing technique aimed at enhancing the mechanical properties of 3D-printed polypropylene-carbon fiber (PP-CF) composite parts. The method involves printing components with internal voids to reduce weight and printing time, subsequently filling these voids with a low-cost resin known for its superior mechanical properties. Through systematic experimentation varying infill density and pattern, key quantitative findings were obtained. Tensile strength generally increased with higher infill density, reaching a maximum of 55.664 MPa for the resin-filled triangle infill pattern with 60% infill density. Impact energy showed a decreasing trend with increasing infill density, with the highest impact energy of 0.5 J recorded for the resin-filled triangle infill pattern with 60% infill density. Microstructural analysis revealed that the triangle infill pattern at 60% infill density exhibited the most effective resin penetration, contributing to superior mechanical performance. These findings emphasize the importance of infill pattern selection in resin distribution and mechanical enhancement in 3D-printed composite materials.