SEARCH RESULT

This study aims to investigate the effect of reduced graphene oxide (rGO) on microstructure, hardness and electrochemical corrosion performance of pure iron. The microstructure investigations were carried by optical and SEM microscopes. The electrochemical corrosion tests were conducted by potentiodynamic polarization test in 3.5% NaCl solution. The results showed that rGO-reinforced sample showed slightly higher hardness value. On the other hand, the corrosion performance of pure iron was significantly improved by the addition of rGO due to the reduced reduction kinetics.

International Iron & Steel Symposium
UDCS

Hüseyin Zengin MUHAMMET EMRE TURAN

- In this study, Cr-W steels were produced by casting then heat treatment was applied for specimens. After the normalization process at 1100 0C for 1 hour, samples were heated up 660 0C and 760 0C to evaluate the effect of tempering temperature. One group of steel were waited at 1 hour and the other group were waited at 2 hours in these temperatures. Hardness of specimens was measured according to the Vickers test method. Wear tests were performed for all specimens under the loads of 10N, 20N and 40N in dry sliding conditions. Microstructure analysis was carried out using Light Optical Microscope (LOM), Scanning Electron Microscope (SEM). Results show that, tempering temperature significantly affects the wear behaviors of samples. These effects can be seen especially under higher loads. And also there is a direct proportion between wear and hardness results

International Iron & Steel Symposium
UDCS

Fatih AYDIN Yavuz Sun MUHAMMET EMRE TURAN Mustafa ACARER Hayrettin Ahlatçı Yunus Türen

Aim of this study is to investigate effect of titanium carbide nanoparticle contents on the mechanical properties of the Aluminum/TiC composites. Aluminum and titanium carbide nanoparticles were mixtured in the turbula mixer. After mixture process, samples were produced using Hot Press in argon atmosphere. Scanning Electron Microscope (SEM) and X-ray diffraction were used for characterization. Compression test was performed for determination of strength and also vickers hardness tests were carried out to understand mechanical effects of TiC particles on pure aluminum.

International Iron & Steel Symposium
UDCS

Yasin Akgül MUHAMMET EMRE TURAN Yuksel Akinay

Abstract Fiber Metal Laminate (FML) with specific strength and low densities, which is a family of hybrid composite structure formed from the combination of metal layers sandwiching a fiber-reinforced plastic layer, have big potential in aeronautical applications in nowadays [1]. Researchers have tried to fabricate laminated composite materials in order to meet demands of industry. Available literature describes already applied laminates consisting of aluminium alloys and glass fibres (GLARE®), carbon fibres (CARALL®) and aramid fibres (ARALL®) [2]–[4]. Today, materials research is moving towards natural fibre composites/laminates. It is because of factors such as low weight, cost effectiveness, man’s desire to go in for natural products, environment friendliness, renewable nature, biodegradability with respect to fiber, and ready use of plants/trees with less processing [5]. The aim of this study is to investigate of microstructural and mechanical performance of metal laminated composite using both natural fibers and industrial fibers as reinforcement. 1050 H24 Aluminum sheet with 0.25 mm thickness was used as matrix material. Silk fabric and S2-glass fiber were reinforced with aluminum separately. Aluminum sheets were cut to suitable size for hot pressing. Mechanical grinding was applied to improve surface roughness and adhesion mechanism. Metal sheets were washed with distilled water and ethanol, respectively. Then they were waited in the chromic acid solution. Epoxy resin and hardener were weighed (100:20 ratio %wt) and mixed homogenously for lamination process. Two different samples for each reinforced composite were prepared for curing process under heat and pressure in the hot-pressing device according to the metal-fiber-metal- fiber-metal stacking sequence (Figure 1) by hand lay-up. The prepared laminate composites were cured at 80 °C and under 1 ton pressure for three hours. Microstructures of laminate composites were characterized using Scanning Electron Microscope (SEM). Samples were prepared for tensile test to examine mechanical properties. Results show that good adhesive bonding was achieved and there were no macro defects such as porosities in microstructure for all specimens. Composites exhibited different mechanical performance (Table 1) and S-2 glass fiber reinforced composite showed best mechanical properties among the specimens. But when the adhesion mechanism of the silk fabric to the resin is improved, it can be used as an alternative natural reinforcement for fiber metal laminates.

International Symposium on Light Alloys and Composite Materials
UHAKS

Mustafa Yunus ASKIN Yunus Türen MUHAMMET EMRE TURAN Yavuz Sun Hayrettin Ahlatçı

Magnesium have an enormous potential for automobile and aerospace industries due to its low density, high specific strength and good damping ability [1]. However, the low wear resistance and low mechanical properties of Mg hinder the use of Mg in industrial applications [2]. To improve these low properties of Mg, Mg metal matrix composites are widely produced with different reinforcements such as SiC [3], B4C [4], Al2O3 [5]. TiC is a reinforcement material with high hardness and extreme wear resistance [6]. However, the investigation of the effect of TiC on mechanical and wear properties is quite limited.

International Symposium on Light Alloys and Composite Materials
UHAKS

Fatih AYDIN Yavuz Sun MUHAMMET EMRE TURAN Hayrettin Ahlatçı Yunus Türen Mustafa ACARER

Magnesium alloys have great potential in aerospace, automotive and electronic industries due to high specific strength and low densities [1], [2]. Because high specific strength and lightweight materials are needed to improve energy efficiency [3],[4]. However, magnesium alloys have poor mechanical properties, so this situation limits the usage of magnesium in practical applications. There have been a lot of attempts by researchers to overcome deficiencies of magnesium alloys, especially for decades. Researchers develop mechanical properties of magnesium by incorporating reinforcement materials. Micron size reinforcements are generally preferred but nowadays, nano-size materials especially carbon based are becoming popular subject for researchers. In this study, graphene nanoplatelets (GNPs) which is an allotrope of carbon is used as a reinforcement material for magnesium matrix composite. Aluminum was also used to evaluate its binding effects on Mg-GNPs composite. Pure Mg, Mg-0.25 wt.% GNPs, Mg-3Al-0.25 wt.% GNPs and Mg- 9Al-0.25 wt.% GNPs composites were fabricated using semi powder metallurgy technique. GNPs was exposed to ultrasonication process in ethanol for an hour in order to break Vander Waals bonding between carbon atoms. Mg-Al powder (mixed in Turbula mixer for two hours) was added to GNPs/Ethanol solution. Powders were mixed using magnetic stirrer which is connected to the vacuum distillation system. Process was continued until the ethanol removed from the system. Then obtained powder was dried in vacuum drying oven. Dried powders were compacted in graphite mold under 50 MPa applied load in hot pressing device. Argon was used to prevent oxidation and pressing, and sintering temperatures were chosen as 550 ºC. Experimental densities were calculated by Archimedes technique. Microstructures of produced samples were characterized using X-ray diffraction and Scanning Electron Microscope (SEM). Hardness test was applied according to the Vickers test method. Compression tests were performed for all samples to investigate mechanical effects of aluminum and GNPs on magnesium-based composite. Results show that uniform distribution of carbon atoms is seen for GNPs reinforced composites. Figure 1 shows SEM images of Mg-3Al-GNPs and Mg-9Al-GNPs composites. Microstructures are free of macro porosities. As shown in Table 1, hardness of pure magnesium is significantly improved with the addition of Aluminum and GNPs. It can be concluded that reinforcement materials may restrict the dislocation motion and aluminum can exhibit lubricant effect between matrix and GNPs. Compression tests reveal that 0.2% Compression Yield Strength (CYS) and Ultimate Compression Strength (UCS) are enhanced with the addition of reinforcement. Thus, mechanical properties of pure magnesium were significantly improved even low content of carbonaceous reinforcement.

International Symposium on Light Alloys and Composite Materials
UHAKS

MUHAMMET EMRE TURAN Yavuz Sun Fatih AYDIN Hüseyin Zengin Yunus Türen Hayrettin Ahlatçı

Abstract Rare earth (RE) additions can improve mechanical properties at room and elevated temperatures, formability and castability of magnesium alloys [1-3]. Recently, numerous studies have been conducted about wrought Mg-Zn-Zr- RE alloys due to their excellent strength and great potential for further development. In this study, microstructure, mechanical and corrosion properties of as-cast and as-extruded Mg-6Zn-0.5Zr (wt%) alloy, also denoted as ZK60, with minor La addition were investigated. Mg-6Zn-0.5Zr-0.2La magnesium alloy was produced by low-pressure die casting method under a protective argon gas atmosphere. Pure Mg (99.9%) ingots were melted at 750 °C and pure Zn (99.7%), Mg-30 wt% Zr and Mg- 30 wt% La master alloys were added into the molten Mg. The melt was held at this temperature for 30 min and stirred for 15 min to ensure a full dissolution of alloying elements. After applying a pressure of 2 bar into the air tight electric resistance furnace, the melt was transferred from the crucible to the steel mould preheated to 250 °C through the rising steel tube and cylindrical ingots with a diameter of 34 mm and length of 190 mm were obtained. After casting, the as-cast alloys were homogenized at 400 °C for 24 h and water quenched. Then, each homogenized billet was machined into cylindrical bar with a diameter of 32 mm and length of 30 mm. For extrusion process, the machined billets and the extrusion die were preheated to the target temperature for 40 min and directly extruded at an initial temperature of 300 °C with an extrusion ratio of 16:1 and a ram speed of 0.3 mm.s-1. Microstructure characterizations were conducted by a Nikon optical microscope (OM) and a Carl Zeiss Ultra Plus field emission scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy (EDS). The constituent phases in the as-cast alloy and the macro-texture of the extruded alloy were characterized by X-ray diffraction (XRD-Rigaku Ultima IV). Tensile tests were conducted on a Zwick/Roell Z600 universal testing machine at a strain rate of 1.67 x 10-3 s-1 at room temperature (RT). The samples for immersion corrosion test (Φ 5 mm x 15 mm) were cut from the half radius of the alloys, followed by grinding and polishing. Then, the samples were immersed in 3.5 wt% NaCl solution at room temperature for 72 h. The electrochemical corrosion tests of the alloys were also performed in 3.5 wt% NaCl solution at room temperature by a Gamry model PC4/300 mA potentiostat/galvanostat with DC105 corrosion analysis.

International Symposium on Light Alloys and Composite Materials
UHAKS

Hüseyin Zengin Yunus Türen MUHAMMET EMRE TURAN Hayrettin Ahlatçı Yavuz Sun

Bu çalışmada yakma kaynağı kullanılarak R260 kalite raylarda birleştirme işlemi yapılmıştır. Kaynak işlemi neticesinde mantar, ağ ve ayak kısmından sertlik ve mikroyapı ölçümleri yapılmıştır. EN 13674- 1 standardına göre bir metrelik raylara (hem orijinal hem de kaynak yapılmış) kalıntı gerilme ölçümü uygulanmıştır. Sonuçlar göz önünde bulundurulduğunda bazı bölgelerde tamamen perlitik mikroyapı elde edilirken ısı tesiri altında kalan bölgelerde kaba östenit yapısı görülmüştür. Kaynak bölgesinin ağ kısımında sertlik daha yüksek çıkmıştır. Bunun sebebi olarak ise kaynak sonrası gerçekleşen kesit alanından kaynaklı hızlı soğumanın etkili olduğu öne sürülmüştür. Kalıntı gerilme olarak çekme kalıntı gerilmeleri mevcut olmakla beraber kaynak sonrasında elde edilen gerilme dağılımında artış görülmüştür. n this study, R260 quality rails were used for the joining process. As a result of the welding, hardness and microstructure measurements were performed from the head, web and foot parts. According to EN 13674-1, residual stress measurement was applied to one meter rails (both original and welded). Considering the results, in some regions, completely perlitic microstructure was obtained and rough austenite structure was observed in the regions under the influence of heat. Hardness was higher in the web part of the weld zone. The reason for this is that fast cooling caused by the lower cross - sectional area after welding has been suggested to be effective. Although tensile residual stresses are present as residual stresses, there is an increase in the stress distribution obtained after welding process.

International Symposium on Railway System Engineering
ISERSE

Harun ÇUĞ Mustafa Dursunlar MUHAMMET EMRE TURAN

Raylar demiryolu alt yapısının en önemli parçasıdır. Demiryolu altyapısında kullanılan raylarda üzerinden geçen yük esnasında meydana gelen gerilmelerin bilinmesi, mekanik özelliklerini ve kullanım ömürlerini tahmin etme hususunda önemli bilgiler vermektedir. Bu çalışmada, demir yolu hattına döşenmiş R260 kalite ve mantarı sertleştirilmiş R350 HT kalite raylarda gerilme ölçümleri yapılmıştır. Gerilme ölçümlerinde özel elektriksel dirence sahip bir aparat olan gerinim ölçerler (strain gauge) kullanılmış ve ölçümler hem düz yolda hem de virajlı kurplarda yapılarak kıyaslamalar yapılmıştır. Sonuçlar değerlendirildiğinde, mantarı sertleştirilmiş raylarda üzerinden yükü ve hızı bilinen vagonlar geçtiğinde meydana gelen gerilim değerleri normal raylara göre daha düşük çıkmıştır. Aradan iki aylık bir süre geçtikten sonra ölçümler tekrarlandığında herhangi bir mekanik hasarın olmadığı benzer gerilme değerlerinin çıkmasıyla anlaşılmıştır. Rails are the most important part of the railway infrastructure. Knowing the stresses that occur during the load passing on the rails used in railway infrastructure gives important information about the estimation of mechanical properties and service life. In this study, strain of R260 quality and head hardened R350 HT quality rails on the rail lines was measured. Strain gauges, which have special electrical resistance, were used in the stress measurements and the measurements were made on both straight and curved curves. When the results were evaluated, the tension values on the head hardened rails were lower than the normal rails when the wagons (the load and speed are known) were passed. After two months, the measurements were repeated, and similar stress values were obtained without any mechanical damage.

International Symposium on Railway System Engineering
ISERSE

MUHAMMET EMRE TURAN Yavuz Sun Hayrettin Ahlatçı SAİT ÖZÇELİK

Ulaşım sektörü, her yönüyle, ülkerin refah düzeyi için belirleyici bir parametredir. Özellikle sanayi ürünlerinin, nakliyesinin kolaylığı ve nakliye maliyetlerinin düşük olması önemlidir. Demiryolu ulaşımı bu noktada kolay, ucuz ve güvenli bir çözümdür. Tabiki bu çözümü uygulayabilmek için de yeterli demiryolu ağı ve altyapıya sahip olmak gereklidir. Bu ihtiyaca binaen, ülkemizde demiryolu sektörüne büyük yatırımlar yapılmaktadır. Demiryollarındaki gelişmelerle beraber ortaya çıkan daha kaliteli malzeme ihtiyaçları ve bu malzemelerin maliyetleri, ihtiyacın yerli kaynaklarla karşılanması fikrini ortaya çıkarmaktadır. Bu bağlamda ülkemizin daha önceden kullanmadığı ya da ithal ederek kullandığı uzun ömürlü rayların yerli kaynaklarla imal edilmesi projelendirilmiş ve TÜBİTAK desteği ile başarılı bir şekilde üretilmiştir. Bu çalışmada, Kardemir A.Ş., Karabük Üniverstesi ve DATEM işbirliği ile, ülkemizde ilk kez EN 13674 standardına göre R350HT kalite mantarı sertleştirilmiş (uzun ömürlü) raylar üretilmiştir. Saha kondüsyonları ve aşınma profilleri incelenmiş, laboratuvar ve servis şartlarındaki başarıları ortaya konulmuştur. The transport sector is a decisive parameter for the welfare of the country in all aspects. Particularly, it is important that the transportation of industrial products, ease of transportation and low transportation costs. Railway transportation is easy, cheap and safe at this point. Of course, it is necessary to have adequate rail network and infrastructure to implement this solution. With this need, large investments are made in the railway sector in our country. The need for higher quality materials and the costs of these materials together with the developments in the railroads brings up the idea of meeting the need with domestic resources. In this context, our country has previously imported or not used to be manufactured with domestic resources long-life rails have been designed and successfully produced with the support of TUBITAK. In this study, the condition and wear profiles of the rugged rails of the R350HT quality mushroom hardened (long life) produced in accordance with the EN 13674 standard were investigated in cooperation with Kardemir AS, Karabük University and DATEM. In this study, in accordance with EN 13674, R350HT quality head hardened (long life) rails were produced for the first time in Turkey in cooperation with Kardemir AS, Karabük University and DATEM. Field conditions and wear profiles were examined and their success in laboratory and service conditions were determined.

International Symposium on Railway System Engineering
ISERSE

Hayrettin Ahlatçı Yavuz Sun İsmail Esen MUHAMMET EMRE TURAN SAİT ÖZÇELİK İBRAHİM TOZLU

Demiryolunun en önemli alt yapısı olan raylarda kaynak ve aşınma olgusu, yük taşıma ve yolcu güvenliği açısından en önemli parametrelerdir. Bu çalışmada yakma kaynağı yöntemiyle demir yolunda yaygın olarak kullanılan R260 kalite raylara kaynak işlemi gerçekleştirilmiştir. Kaynak işleminin ardından ileri geri aşınma yöntemi uygulanarak aşınma dayanımı incelenmiş ve kaynaksız aynı kalite rayla kıyaslanmıştır. 2 farklı yük uygulanması neticesinde aşınma performansları değerlendirilmiş, mantar, ağ ve ayak kısımlarının aşınma sonuçları kayıt altına alınmıştır. Ağ kısmında aşınma hızının kaynak sonrası yüksek soğuma hızından dolayı daha düşük olduğu, mantar ve ayak kısmında ise rayların birbirlerine yakın aşınma performansları sergilediği tespit edilmiştir. The most important substructure of the railway is the welding and wear phenomenon on rails are the most important parameters in terms of cargo transportation and passenger safety. In this study, welding process was applied to R260 quality rails which are commonly used in the railway using the method of flash butt welding. After welding process, the abrasion resistance was investigated by applying reciprocating wear technique and compared with the same quality rail without welding. Wear performance was evaluated as a result of the applied two different loads and the wear results of head, web and foot parts were recorded. It has been determined that the wear rate in the web is lower due to the high cooling rate after welding, while in the head and foot part of the rails show close wear performances.

International Symposium on Railway System Engineering
ISERSE

Harun ÇUĞ MUHAMMET EMRE TURAN