Davut, Kemal
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Davut, K.
K.,Davut
K., Davut
Davut,K.
D., Kemal
Davut, Kemal
D.,Kemal
Kemal, Davut
K.,Davut
K., Davut
Davut,K.
D., Kemal
Davut, Kemal
D.,Kemal
Kemal, Davut
Job Title
Doktor Öğretim Üyesi
Email Address
kemal.davut@atilim.edu.tr
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Scopus Author ID
Turkish CoHE Profile ID
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Scholarly Output
22
Articles
14
Citation Count
201
Supervised Theses
3
22 results
Scholarly Output Search Results
Now showing 1 - 10 of 22
Article Citation Count: 9Machinability evaluations of austempered ductile iron and cast steel with similar mechanical properties under eco-friendly milling conditions(Elsevier, 2021) Yılmaz, Okan Deniz; Davut, Kemal; Cetin, Baris; Ucak, Necati; Cicek, Adem; Yilmaz, Okan Deniz; Davut, Kemal; Department of Metallurgical and Materials Engineering; Manufacturing EngineeringIn engineering applications, to increase productivity and to decrease production costs, the selection of the proper engineering material is essential. At that point, machining operations directly affect the production costs. Therefore, determination of the material with the desired mechanical properties and easy-to-cut characteristics has a critical importance. This situation is currently gaining more importance in especially defense industry applications in which high strength engineering materials are heavily employed. In addition, tool performance and final product quality are directly influenced by the cooling and/or lubrication conditions in particularly interrupted cutting operations. In this study, machinability characteristics of G18NiMoCr3-6+QT1 cast steel (CS) and 1050-6 austempered ductile iron (ADI) with similar mechanical properties during milling operations were investigated. The tests were performed using TiAlN coated cemented carbide (WC-Co) end mills under dry, conventional cutting fluid (CCF), and minimum quantity lubrication (MQL) conditions. Under each condition, the variations of cutting forces, tool wear, average surface roughness (Ra), and subsurface microstructure and microhardness were analyzed for both materials and then compared to one another. Test results showed that 1050-6 ADI led to further tool wear in comparison to G18NiMoCr3-6+QT1 CS. According to obtained results, dry condition is more favorable than CCF and MQL conditions in terms of cutting forces, surface roughness, and tool wear for both types of material. In addition, examinations on subsurface microstructures showed that MQL conditions provided an effective cutting environment to maintain microstructural stability of workpiece materials. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Article Citation Count: 12Understanding Corrosion Morphology of Duplex Stainless Steel Wire in Chloride Electrolyte(Mdpi, 2021) Davut, Kemal; Davut, Kemal; Kocabas, Mustafa; Bayatli, Aleyna; Urgen, Mustafa; Department of Metallurgical and Materials EngineeringThe corrosion morphology in grade 2205 duplex stainless steel wire was studied to understand the nature of pitting and the causes of the ferrite phase's selective corrosion in acidic (pH 3) NaCl solutions at 60 degrees C. It is shown that the corrosion mechanism is always pitting, which either manifests lacy cover perforation or densely arrayed selective cavities developing selectively on the ferrite phase. Pits with a lacy metal cover form in concentrated chloride solutions, whereas the ferrite phase's selective corrosion develops in diluted electrolytes, showing dependency on the chloride-ion concentration. The pit perforation is probabilistic and occurs on both austenite and ferrite grains. The lacy metal covers collapse in concentrated solutions but remain intact in diluted electrolytes. The collapse of the lacy metal cover happens due to hydrogen embrittlement. Pit evolution is deterministic and occurs selectively in the ferrite phase in light chloride solutions.Conference Object Citation Count: 3A Potential Solution to Mystical Materials in Indentation Test(Elsevier Science Bv, 2017) Billur, Eren; Davut, Kemal; Music, O.; Simsir, C.; Şimşir, Caner; Music, Ömer; Department of Metallurgical and Materials Engineering; Automotive Engineering; Manufacturing EngineeringVarious methods have been designed to determine the elasto-plastic properties of metals. Instrumented indentation test (IIT) is considered to be a good candidate to determine local properties after manufacturing operations. In order to acquire elastoplastic properties from IIT, either dimensional analysis or inverse analysis of the force-displacement curve is performed. However, the major drawback of those methods is the uniqueness of the solution. Some materials may exhibit almost identical force-depth curves, although they have different elastoplastic properties. Those materials are referred as "mystical materials". In this contribution, topological features of the indentation surfaces, i.e. indent size, pile-up and sink-in behaviour, are investigated to find a differentiating property. According to the results, indent size, pile-up and sink-in behaviour may help to find the unique solution to the inverse problem. (C) 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the International Conference on the Technology of Plasticity.Article Citation Count: 2Development and properties of austempered low alloyed white cast iron(Walter de Gruyter GmbH, 2021) Davut, Kemal; Davut,K.; Kilicli,V.; Department of Metallurgical and Materials EngineeringThis study examined the response of low-alloy white cast iron to austempering heat treatment. In addition, it investigated the microstructure and mechanical properties of austempered low-alloy white cast iron. The low-alloy white cast iron specimens were austenitized at 900 °C, followed by quick quenching into a salt bath at 375 °C, and held there for 15 to 120 minutes for austempering heat treatment. Microstructural features were studied by optical, scanning electron microscopes, and XRD analysis. The mechanical properties were determined by hardness and unnotched Charpy impact toughness tests. As a function of those austempering times, a microstructural map was constructed to show how the transformation products develop, quantitatively. The experimental results showed that the austempering heat treatment produced a microstructure consisting of eutectic carbides + ausferritic structure in low-alloy white cast iron. It can be concluded that the low-alloy white cast iron can be austempered, similar to ductile cast irons. Improved hardness and impact toughness values have been obtained in austempered low-alloy white cast iron. © 2021 Walter de Gruyter GmbH, Berlin/Boston, Germany.Article Citation Count: 1Nondestructive microstructural characterization of austempered ductile iron(Walter de Gruyter Gmbh, 2023) Davut, Kemal; Yalcin, Mustafa Alp; Davut, Kemal; Kilicli, Volkan; Department of Metallurgical and Materials EngineeringAustempered 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.Master Thesis Rulman çeliklerinin manyetik Barkhausen gürültüsü yöntemi ile tahribatsız karakterizasyonu(2017) Davut, Kemal; Davut, Kemal; Şimşir, Caner; Department of Metallurgical and Materials Engineering100Cr6 çelikleri rulman yapımında yaygın olarak kullanılırlar. Isıl işlem uygulamaları ile değişen iç yapısal özelliklerine bağlı olarak; yüksek gerilimlere karşı dayanımı, yorulma ömrü, tokluğu, sertliği, aşınma direnci gibi özellikleri geliştirilebililir. Bu iç yapısal özelliklerin muayenesi, geleneksel metalografik ve XRD tekniklerinin bir arada kullanılmasıyla yapılabilir. Ancak bu yöntemler numune hazırlama gereksinimi bulunan yöntemlerdir. Bu sebepten; tahribatsız ve hızlı ölçüm alınmasını sağlayan Manyetik Barkhausen gürültüsü (MBN) tekniği, bu geleneksel karakterizasyon yöntemlerine alternatif olarak değerlendirilmiştir. Bu çalışmanın amacı 100Cr6 çeliklerinin MBN yöntemiyle tahribatsız muayene edilebilirliğinin araştırılmasıdır. Bu bağlamda, 100Cr6 çelik numuneler, içerisinde farklı içyapısal özelliklerin oluşturulabilmesi adına farklı sıcaklıklarda östenitlenip oda sıcaklığına ve -130°C'ye hızlı soğutulmuştur. Bu işlemlerin ardından numunelerin sertliği, karbür miktarları, dağılımları, kalıntı östenit miktarları, metalografik ve XRD ölçüm yöntemleriyle belirlenmiştir. Ayrıca, her bir numune MBN yöntemi ile de muayene edilmiştir. Son olarak, elde edilen içyapı sonuçlarıyla MBN sonuçları arasındaki bağlantılar incelenmiştir. MBN tekniğinin, kurulan lineer korelasyonlar kapsamında oda sıcaklığına hızlı soğutulan 100Cr6 çelik numunelerin iç yapısal özellikleriyle korele edilebilir olduğu gözlenmiştir; ancak tahmin aralıklarının oldukça geniş olması sebebiyle, bu numunelerin iç yapısında oluşan sertlik, kalıntı östenit ve karbür miktarıların doğrudan belirlenebilmesi için yeterince hassas olmadığı sonucuna varılmıştır. Birbirlerine bağlı olarak değişen bu özelliklerin MBN ile karakterize edilebilmesi; karbür çözünme kinetiğine bağlı olarak, tüm bu değişkenlerin hem kendi aralarında hem de MBN sinyalleri üzerindeki eş zamanlı etkileri arasında lineer olmayan bir ilişki kurulması ile mümkün olabileceği düşünülmektedir. Bunun haricinde, sıfır altı ısıl işlemine tabi tutulan numunelerde, kalıntı östenitin tamamen yok edilmesi, MBN sinyalleri üzerindeki kalıntı östenit etkisini tamamen ortadan kaldırılmıştır. Bu sebepten hem sertlik ve hem de kardür oranları için kurulan lineer korelasyonlarda belirgin bir iyileşme görülmüştür. Bu korelastonların R² değerleri kabul edilebilir düzeyde olmasına rağmen tüm iç yapısal değişkenlerin MBN sinyalleri üzerindeki eş zamanlı etkisi göz önünde bulundurularak lineer olmayan modeller kurulmasıyla iyileştirilebilinir. Bu doğrultuda, MBN tekniğininin, 100Cr6 çeliğinin iç yapısal karakterizasyonu konusunda, gelecekte yapılacak daha detaylı ve kapsamlı çalışmalar ile geliştirilebilir olduğu düşünülmektedir.Master Thesis Östemperlenmiş küresel grafitli dökme demirlerde alaşımlama ve ısıl işlem parametrelerinin optimizasyonu(2019) Davut, Kemal; Davut, Kemal; Department of Metallurgical and Materials EngineeringÖstemperlenmiş küresel grafitli dökme demir sunduğu yüksek mukavemet, tokluk ve aşınma direncine ek olarak düşük yoğunluk ve maliyet avantajı sayesinde mühendislik tasarımlarında yoğun olarak kullanılmaktadır. Bu malzemelerin güçlü mekanik özelliklerinin nedeni, ösferritik matris üzerinde küresel grafitlerden oluşan özel mikroyapısıdır. Östemperleme ısıl işlemi sonrasında oluşan ösferrit yapısı, iğnemsi ferrit ve karbonca zengin kararlı östenitten oluşmaktadır. Düşük küresellik değerleri ya da iğnemsi ferrit dönüşümünün eksik kalması nedeniyle östenit yapısının yeterince kararlı hale gelmemesi gibi sorunlar mikroyapıyı bozmakta ve mekanik özellikleri olumsuz etkilemektedir. Bu çalışmada Cu ve Cu + Mo + Ni alaşım elementlerinin, ısıl işlem parametrelerinin ve küresel grafit parçacıklarının boyutları ve dağılımlarının, östemperlenmiş küresel grafitli dökme demir malzemelerin mikroyapısına ve mekanik özelliklerine etkisi incelenmiştir. Bunun için, düşük alaşımlı ve düşük alaşıma Cu, Cu + yüksek Mo + düşük Ni ve Cu + düşük Mo + yüksek Ni elementleri eklenmiş Y-blok dökümler üretilmiştir. Y-blok parçalardan çıkarılmış numuneler östemperleme ısıl işleminden geçirilmiş; daha sonra mekanik testler yapılmış, kırılma yüzeyi ve metalografik incelemeler gerçekleştirilmiştir. Sonuçlar, Cu + düşük Mo + yüksek Ni ile alaşımlanmış numunenin daha yüksek mukavemet ve uzama değerlerine sahip olduğunu göstermektedir. Bu da, Cu ve Cu + Mo + Ni alaşımları eklenmiş parçaların karbonca zengin ve kararlı östenit yapısına sahip olduğunu; ve geniş kesit alana sahip parçalarda bile kalınlık boyunca homojen bir ösferritik yapı oluşturulabileceğini göstermektedir. Düşük alaşımlı numune ise, yetersiz alaşımlama ve östemperleme işlemi nedeni ile en iyi küresellik ve sertlik değerlerine sahip olmasına rağmen en düşük mukavemet ve uzama değerlerini vermektedir. Mekanik özelliklerdeki bu değişkenliğin, mikroyapıda bulunan kalıntı östenitin yapısı, miktarı ve dağılımı ile doğrudan bağlanıtılı olduğu gözükmektedir. Son olarak, Pearson Korelasyon Katsayısı yöntemi kullanılarak malzemenin mekanin özellikleri ve mikroyapısı arasındaki ilişki incelenmiştir. Sonuçlar, östenit tane boyutu ve akma dayancı, çekme dayancı ve süneklik arasında Hall-Petch benzeri bir ilişki göstermektedir. EBSD çalışmaları sonrasında iki farklı tip östenit yapısı görülmüştür: i) iğnemsi ferrit yapıları arasında kalmış ince östenit ve ii) östemperleme işlemi sırasında dönüşmemiş önceki östenit tanelerinden kalan blok tipi östenit. Çalışılan numuneler arasında, iğnemsi ferrit tane boyutu 0.7 m'den daha az değişkenlik göstermektedir. Bu nedenle iğnemsi ferrit tane boyutu ile mekanik özellikler arasında iyi bir korelasyon gözükmemektedir. Küresellik ve küresel grafitlerin boyutu arasında ise yüksek korelasyon gözükmektedir. Küresellik derecesindeki küçük farklar mekanik özellikleri etkilememekle beraber, küçük küresel grafit taneleri hem akma hem de çekme dayancı değerlerini iyileştirmektedir. Bu sonuçlar östemperlenmiş küresel grafitlli dökme demirlerin daha da geliştirilmesi ve iyileştirilmesine katkı sağlayabilir.Conference Object Citation Count: 0Effect of batch and continuous annealing processes on crystallographic texture and formability of an if steel(Association for Iron and Steel Technology, AISTECH, 2017) Davut, Kemal; Baskaya,U.; Davut,K.; Department of Metallurgical and Materials EngineeringIF (interstit ial free) steels are used in many applicatio ns, specifically in automotive industry due to their excellent formability. This formability behaviour is directly related to the annealing process, which influences both the crystallographic texture and the related "r value". For annealing, two main routes, namely batch and continuous annealing processes, are used in the production of IF-steels. The present study aims at comparing the same grade of IF steels produced via batch and continuous annealing processes. For this purpose, the texture and microstructure analysis were performed by electron backscatter diffraction (EBSD) technique in a scanning electron microscope (SEM). The formability behaviour of the steel sheet was characterized by determining the hardening curve and yield surface. It has been found that all samples show a strong ND fiber; {111}//ND. On the other hand, the drawability and related "r value" of continuously annealed samples were better than batch annealed ones. This behaviour is explained by the ultra-low carbon content, lower yield strength and equiaxial grain structure. © Copyright 2017 MS&T17®.Article Citation Count: 2A comprehensive characterization of the effect of spatter powder on IN939 parts fabricated by laser powder bed fusion(Elsevier Sci Ltd, 2023) Özer, Seren; Mussatto, Andre; Doğu, Merve Nur; Davut, Kemal; Davut, Kemal; Obeidi, Muhannad Ahmed; Brabazon, Dermot; Metallurgical and Materials Engineering; Department of Metallurgical and Materials EngineeringThis study is focused on a comprehensive characterization of virgin and spatter IN939 powders and the effects of a certain amount of spatter powder on the part quality of IN939 fabricated by the L-PBF process. A brown tint coloration formed Al2O3 oxide, pores, a 124.4% increase in the average particle size, a 10.2% decrease in the powder circularity, and a 7.5% decrease in the powder aspect ratio were observed in the spatter powder. Additionally, higher average grain size and lower nanohardness were obtained for the spatter powder. In order to understand the effect of a certain amount of spatter powder on the part quality, 10 wt% spatter powder was mixed with the virgin powder. This addition was found to decrease the flowability of the powder. Moreover, this addition decreased relative density by around 0.3% and increased surface roughness by around 80.8% in the fabricated samples (termed as V and SV). On the other hand, there was no considerable microstructural, texture, microhardness, and nanohardness difference between V and SV samples, although the spatter powder addition caused a 30.2% increase in the average grain size of SV. The overall texture for both V and SV samples exhibit (00 1)//BD.Article Citation Count: 70Wire arc additive manufacturing of high-strength low alloy steels: study of process parameters and their influence on the bead geometry and mechanical characteristics(Springer London Ltd, 2020) Davut, Kemal; Davut, Kemal; Koc, Baris; Yilmaz, Oguzhan; Department of Metallurgical and Materials EngineeringAdditive manufacturing (AM) is becoming increasingly popular since it offers flexibility to produce complex designs with less tooling and minimum material at shorter lead times. Wire arc additive manufacturing (WAAM) is a variant of additive manufacturing which allows economical production of large-scale and high-density parts. The WAAM process has been studied extensively on different steels; however, the influence of process parameters, specifically wire feed speed (WFS), travel speed (TS), and their ratio on bead geometry, microstructure, and mechanical properties, are yet to be studied. The present work aims at closing this gap by using the WAAM process with robotic cold metal transfer (CMT) technology to manufacture high-strength structural steel parts. For that purpose, single-bead welds were produced from HSLA steel by varying WFS between 5 and 10 m/min and the WFS to TS ratio between 10 and 20. Those variations produce heat inputs in the range of 266-619 J/mm. The results have shown that the wire feed speed to travel speed ratio is the major parameter to control the heat input. Increasing heat input increases characteristic bead dimension, whereas it reduces the hardness. In the second part of experiments, two single-bead walls were deposited via the parallel deposition strategy and one multiple-bead wall was produced using the oscillation strategy. The tensile properties were tested along two directions: parallel and perpendicular to deposition directions. For the yield strength and tensile strength, the difference between horizontally and vertically tested specimens was smaller than the standard deviations. On the other hand, the total and uniform elongation values exhibit up to 10% difference in the test direction, indicating anisotropy in ductility. Those tensile properties were attributed to repeated thermal cycles during the WAMM process, which can cause heat transfer in multiple directions. The yield strength of the multiple-bead wall produced via oscillation was lower, whereas its ductility was higher. The tensile properties and hardness differences were found to correlate well with the microstructure.
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