Yazar "Topçu, İsmail" seçeneğine göre listele

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    Determination of the mechanical properties of al/mwcnt composites obtained with the reinforcement of cu-coated multiwall carbon nanotubes (mwcnts)
    (Inst Za Kovinske Materiale I In Tehnologie, 2020) Topçu, İsmail
    In this study, Al/MWCNT composites were produced by milling copper-coated MWCNTs in small amounts (2.5-7.5%) with aluminum powders using the mechanical alloying method. Then, sintering was applied to the composite material. A phase analysis and microstructure investigations were performed on the as-sintered samples. A hardness test was conducted and tribological performances of the unreinforced and MWCNT-reinforced composites were examined at room temperature. Results showed that the hardness of the base-aluminum alloy was improved. The phase belonging to the MWCNTs was detected with an X-ray diffraction analysis. The wear rate generally decreased with the addition of MWCNTs in all test conditions. Sintering had a positive effect, enhancing the wear and hardness behaviour. Abrasive, adhesive, oxidative and thermal wear mechanisms were observed with a scanning electron microscope (SEM).
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    Effect of multiwalled carbon nanotubes on elevated temperature tensile and wear behavior of Al2024 matrix composites fabricated by stir casting and hot extrusion
    (Springer, 2020) Turan, Muhammet Emre; Rashad, Muhammad; Zengin, Huseyin; Topçu, İsmail; Sun, Yavuz; Asif, Muhammad
    In this study, aluminum alloy matrix composites reinforced with MWCNT particles by 0.5 wt.% were fabricated by a new developed technique, consisting of semi-powder metallurgy and stir casting processes. Then, hot extrusion process was applied to the composite materials. Phase analysis and microstructure investigations were performed for the as-cast and extruded samples. Hardness test was conducted, and tensile tests were applied at room, 150 and 250 degrees C. The tribological performances of unreinforced alloy and MWCNT-reinforced composite were examined at room, 150 and 250 degrees C as well. The results showed that hardness of base aluminum alloy was improved. The peaks belonging to the MWCNT were detected by x-ray diffraction (XRD) analysis. The incorporation of MWCNT presents strengthening effect on the mechanical properties at all test temperatures. The wear rate generally decreased with the addition of MWCNT for all test conditions. Extrusion process had a positive effect to enhance wear and hardness behavior. Abrasive, adhesive, oxidative and thermal wear mechanisms were observed by scanning electron microscope.
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    Experimental investigation on mechanical properties of Multi Wall Carbon Nanotubes (MWCNT) reinforced aluminium metal matrix composites
    (Korean Assoc Crystal Growth, Inc, 2020) Topçu, İsmail; Ceylan, Muhammet; Yılmaz, Elif Burcu
    The aim of this research is to obtain better micrographs and to perform the mechanical characterization of Multi Wall Carbon Nanotubes (MWCNT) consolidated aluminum matrix composite (AMC). This research is focused on the mechanical behavior and microstructure characteristics in MWCNT consolidated aluminum matrix composites. The composites of MWCNT/Al were successfully fabricated using powder metallurgy (PM) mechanical alloying (MA) sintering. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) micrographs were utilized in order to determine the porosity, density and hardness characteristics to observe if they are affected or not concerning the performance of composites in different reinforced % MWCNT rate conditions. Along with SEM and XRD studies, this study details the homogeneous distribution of nanotubes which showed no evidence of decomposition; this was supported by a successive increase in hardness and abrasion resistance. This increase in abrasion resistance and hardness can be accredited to the further activation of the slip system due to the presence of MWCNTs. Based on the conclusions of this study, the authors determined that the mechanical alloying sintering method provides promising results for the mechanical alloying fabrication of MWCNT/Al composites, especially due to the different % rate reinforced up capabilities.
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    Investigation of creep behavior of CNT reinforced Ti6Al4V under dynamic loads
    (Chem Soc Pakistan, 2020) Topçu, İsmail; Çetiner, Burcu Nilgün; Güllüoğlu, Arif Nihat; Gülsoy, Özkan
    This study investigates the effects of addition of Carbon nanotube (CNT) at different volume ratios (0.5- 5%) into Ti6Al4V matrix by mechanical alloying in terms of the density, microstructure, hardness and creep under dynamic load. As a result of the good bonding of carbon nanotubes powders with the main matrix, Ti-6Al-4V/CNT composites have experienced change both in microstructure and mechanical properties (such as hardness, density) and, correspondingly, qualitatively creep behaviour of Ti-6Al-4V matrix alloy has been improved compared to the lean one. The density of CNT reinforced Ti6Al4V composites sintered at 1300 degrees C for 3h decreases with increasing CNT content. The hardness tests indicated that the hardness of composites increased with CNT addition. In addition, although creep strain is decreased continually with CNT content until 5%, creep life increased with increasing CNT content until 4% of CNT but decreased above 4%. After sintering at 1300 degrees C under vacuum for 3 hours the density of the composite material reached to a level of 98.5 %, the microhardness to 538 HV and the creep behaviour was improved. The characterization of Ti6Al4V/CNT composites after mechanical alloying was carried out using scanning electron microscopy (SEM), energy dispersive x-rays spectroscopy (EDS) analysis and X-ray diffraction (XRD) methods. Although Ti-6Al-4V alloys are used as biomaterial, this study aimed at using MWCNTs containing Ti-6Al-4V composites at high temperature applications. Because MWCNTs reinforced Ti-6Al-4V composites are cheaper and have lower weight than the other materials used in this kind of applications.
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    Investigation of wear behavior of particle reinforced AL/B4C composites under different sintering conditions
    (Univ North, 2020) Topçu, İsmail
    In this study, the effects of different sintering conditions of boron carbide reinforced to aluminum matrix powder on microstructure, density and wear resistance by a mechanical alloying method were researched. Powders produced by mechanical alloying for eight hours at the atrial shaft were compressed with a cold isostatic press die under 350 MPa to obtain cylindrical composite specimens. The raw samples were sintered in high purity argon at 600, 625, 650 degrees C for 90 minutes. The wear behavior of the Al/B4C metal matrix composite was studied using a pin-on-disk wear tester. Under favorable conditions, it has been observed that reinforced boron carbide wear can be reduced by more than two decades. Various investigations have been made to relate this improved wear performance to reinforcement ratios. Aluminum abrasion test results showed that different types of abrasion occurred and that the abrasion resistance was increased by the change of the bubble rate. In the experimental studies that were carried out, it was observed that wear resistance increased with the proportion of boron carbide reinforced directly by the weight, and especially with a 15% B4C ratio depending on the increased reinforcement ratio.
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    Karbon nanotüp takviyeli Ti-6Al-4V/KNT kompozitlerin aşınma davranışlarının incelenmesi
    (2019) Topçu, İsmail; Güllüoğlu, Arif Nihat; Bilici, M. Kemal; Gülsoy, H. Özkan
    Bu çalışma da mekanik alaşımlama yöntemiyle Titanyum (Ti-6Al-4V) tozuna takviye edilen Karbon Nanotüplerin farklı üretim sinterleme koşullarının mikroyapı, yoğunluk ve aşınma direnci üzerine etkileri incelenmiştir. Mekanik alaşımlama ile üretilen tozlar, soğuk izostatik pres kalıbı ile 250 MPa basınç altında sıkıştırılarak silindirik kompozit numuneler elde edilmiştir. Üretilen ham numuneler, 1275°C'de 60 dakika süre ile yüksek saflıktaki argon ortamı ve yüksek vakum (1,2 10-5 mbar) altında sinterlenmiştir. Ti-6Al-4V/KNT metal matrisli kompozitin aşınma davranışı pin-on-disk aşınma test cihazı kullanılarak incelendi. Farklı sinterleme sıcaklıklarında elde edilen Ti-6Al4V /KNT alaşımlarının aşınma davranışları üzerindeki etkileri incelenmiştir. Uygun koşullar altında takviyeli Karbon Nano Tüp 'ün aşınma oranını iki dereceden fazla azaltabileceği görülmüştür. Bu geliştirilmiş aşınma performansını takviye oranları ile ilişkilendiren çeşitli araştırmalar yapılmıştır. Ti-6Al-4V kompozitlerin aşınma deney sonuçları, karbon nano tüp oranlarının değişimi ile farklı aşınma türlerinin oluştuğu ve aşınma direncini arttırdığı gözlenmiştir. Yapılan deneysel çalışmalarda aşınma direnci doğrudan hacimce takviye edilen % v/v Karbon Nano Tüp oranları ile değiştiği ve artan takviye oranına bağlı olarak arttığı ancak %5 KNT oranı ile malzemede artan aglomerasyon sonucu bu özeliklerde azalış görülmüştür.
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    TIG ve MIG kaynağı ile işlem gören 304 ve 1040 çeliklerin ITAB bölgesindeki mekanik özelliklerin incelenmesi
    (2019) Topçu, İsmail
    Bu çalışmada düşük ve orta karbonlu çelik türlerinin TIG ve MIG kaynağı ile kaynak bölgesinin mekanik ve mikroyapı özelliklerine kaynak parametrelerinin etkileri incelenmiştir. Kaynak uygulaması farklı akım ve tel besleme hızlarında gerçekleştirilmiş, ardından kaynaklı birleştirmelerin mekanik özelliklerini belirlemek için çekme deneyi ve sertlik ölçümleri yapılmıştır. Ayrıca mikroyapıda meydana gelen değişiklikleri belirlemek için de mikroyapı çalışmaları yapılmıştır. Bu araştırmanın amacı öncelikle kaynak tekniklerinin malzeme kaynaklanabilirliğini nasıl etkilediği ve kaynaklı çeliklerin ısıdan etkilenen bölgede (ITAB) mekanik özelliklerini ve mikroyapı karakteristiklerindeki değişimi incelemektir. Bazı metal ve kaynaklı çeliklerin mekanik özelliklerinin tayini için testler arasında karşılaştırmalar yapılmıştır. Mikroyapılar da, kaynakların performansını dinamik koşullarda etkileyebilecek herhangi bir gözenekliliğin ve diğer özelliklerin tayinine yardımcı olmak için de kullanılmıştır.
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    Wear behavior of irregular shape Ti6Al4V powder reinforced with carbon nanotubes
    (Korean Assoc Crystal Growth, Inc, 2020) Ceylan, Muhammet; Topçu, İsmail
    The purpose of this study was to investigate the sintering behavior, microstructural evolution, and the effect on wear resistance of carbon nanotubes (CNT) with the addition of a mechanical alloy (Ti6Al4V) and sintered irregular Ti64 powder. The mechanical alloy powders utilized in this study were produced through the process of CIP (Cold Isostatic Press) in order to produce samples by compress on under various pressures within a 300 MPa floating molded press. The samples were sintered at a high vacuum (10-5 mbar) for 60 minutes at a temperature of 1275 degrees C. After sintering, the materials were characterized using an optic microscope (OM), scanning electron microscopy (SEM) and EDX (Energy-dispersive X-ray spectroscopy) to determine whether the materials had wear resistance, density measurement, etc. The Carbon Nanotube wear and friction behavior were investigated under various conditions using a pin wear tester on a disc followed by a scanning electron microscopy (SEM) analysis. The objective of this study was to evaluate the density, metallographic properties and hardness of Ti64 samples supplemented with different CNT ratios as a function of sintering temperature. Theoretical density and micro-hardness of mechanical alloyed and sintered irregular Ti64 powders changed with the additions to CNT under increased sintering temperatures.