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8620 kalite çeliklerin sertlik ve korozif aşınma direncine bor ilavesinin etkisi
(2021) Çevik, Engin; Sariçam, Ferhat; Sun, Yavuz; Çarboga, Cemal; Çiçek, Bünyamin
Bu çalışmada; farklı oranlarda bor ilave edilen 8620 kalite ticari çeliklerin korozif aşınma davranışlarının belirlenmesi amacıyla %3,5 sodyum klorür (NaCl) çözeltisi içerisinde farklı yükler (10, 20 ve 40 N) altında korozif aşınma deneyleri gerçekleştirilmiştir. Sonrasında yüzey pürüzlülüğü ölçümleri yapılmış ve buradan elde edilen sonuçlar kullanılarak numunelerde meydana gelen hacimce kayıplar belirlenmiştir. Numunelerin aşınma karakteristikleri taramalı elektron mikroskobu (SEM) ile analiz edilmiştir. 8620 kalite çeliklerin sertlik ve korozif aşınma davranışları incelendiğinde optimum bor oranı 48 ppm olarak tespit edilmiştir
Applicability of different powder and polymer recipes in a new design powder injection molding system
(Walter De Gruyter Gmbh, 2021) Cicek, Bunyamin; Sun, Yavuz; Turen, Yunus; Ahlatci, Hayrettin
Production methods are changing day by day with the developing technology. Based on this idea, a new production logic and machine have been developed owing to polymer-supported powder injection molding (PIM). The ability of this newly designed machine (newPIM) to mold metal or ceramic powders supported by polymer binders is discussed in this study. By taking advantage of the polymer properties such as fluidity and sticking, powders are molded with a specially developed machine with high gas pressure in certain sizes. In this study, in which many parameters are processed from feedstock (FS) production to molding; metals Mg/316L and ceramics SiC/SiO2 powders have been used in different powder sizes and structures. In the newPIM process, polymers were included in four different recipes. Paraffin wax (PW), polyethylene glycol (PEG), polypropylene (PP), ethylene-vinyl acetate (EVA), poly-methyl methacrylate (PMMA) and low-density polyethylene (LDPE) have been employed in the FS with different combinations. From FS production to the molding stage; pressure, microstructure examination, weight loss, and density change features were investigated. The result indicated that the best FS and molding was obtained by the PEG+PMMA polymer composition formed with a spherical powder with a diameter below 40 mu m. The compression force of the FS in this composition was observed at approximately 3.4k N values.
A basic study on artificial aging in Mg-10Al12Si+1Pb alloy
(Iop Publishing Ltd, 2020) Cicek, Bunyamin; Aydogmus, Tuna; Sun, Yavuz
In this study, research has been made on the aging of metal matrix composite materials produced by the in situ casting system. Mg matrix composite material was produced by the in situ casting system. In this study, 90%Mg + 10% Al12Si (wt) ingot casting was performed for alloy formation and 1% Pb was added as an alloying element to the melted structure. This study aims to examine the effect of the artificial aging (AA) process on hardness and microstructure after alloying and composite of Mg metal. The in situ casting system was used in the casting of Mg alloy under the Ar gas atmosphere. The material after required casting homogenization process; for the AA process, they were embedded in a powder graphite filled vessel and kept at 350 degrees C for 1 h and then quenched (with 25 degrees C water). Later; after quenching, the materials were kept at 150 degrees C for 2, 4, 12, 16 and 24 h and aged samples were obtained. Microstructure images were obtained from the samples by scanning electron microscope (SEM) and light optical microscope (LOM) and then the hardness values of the micro hardness device were measured. Grain structure because of AA heat treatment; showed changes according to un-aging material. The hardness value is directly proportional to the increasing aging time of the materials applied to the AA process; it was found that the levels increased approximately to 45% (86HV to 125HV) compared to the un-aging material and passed to the fixing phase.
A COMPARATIVE STUDY ON THE MECHANICAL AND CORROSION PROPERTIES OF THE ZM20 AND ZM21 ALLOYS AFTER CASTING AND ROLLING
(Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2022) Goren, Haul Ahmet; Unal, Mehmet; Turen, Junus; Ahlatci, Hayrettin; Sun, Yavuz
In this study, the effects of grain refinement and production methods on the corrosion, corrosive wear and mechanical properties of the as-cast and as-rolled Mg-2 wt.% Zn (ZM20) and Mg-2 wt.% Zn-0,51 wt.% Mn (ZM21) alloys were examined by using OM, XRD, SEM, hardness and uniaxial tensile test. Additionally, the potentiodynamic polarization, immersion corrosion test and corrosive wear properties of the ZM20 and ZM21 alloys were compared. According to the XRD results, MgZn and MgZn2 phases were found in the alloys and also MnZn3 phase occurred in the ZM21 alloy with the addition of manganese. Both during solidification forming nucleation points with the added manganese and during rolling the broken secondary phase particles distributed into the matrix prevented grain growth and led to the formation of a more refined structure. The tensile test results showed that the strength of the as-cast ZM21 alloys were better than that of the as-cast ZM20 alloys and further improvement in mechanical properties occurred with the rolling of the both alloys. The most superior hardness was found in the as-rolled ZM21 alloy. In the total 400-m recipro-cal corrosive wear test in the 3.5% NaCl solution, the lowest mass loss was in the as-rolled ZM21 alloys. In the potentiodynamic corrosion test, the highest corrosion resistance was occurred by the as-cast ZM20 alloy.
Corrosion and Wear Behaviour of Boronized high Carbon and Chromium Cast Steel
(Iron Steel Inst Japan Keidanren Kaikan, 2013) Ahlatci, Hayrettin; Yargul, Gorkem; Cug, Harun; Cevik, Engin; Yasin, Suleyman; Sun, Yavuz
The purpose of this study was to examine the effect of boronising heat treatment on the corrosion behaviour (in two different corrosive media) and wear properties (on two different counter sliding discs) of the DIN 1.4777 quality cast steel containing 1.7% C, 30% Cr and 1.1% Si. The steel supplied as cast was exposed to homogenisation heat treatment at 1150 degrees C for 3,5 hours and then to boronising heat treatment at 900 degrees C for 8 hours using the powder of Ekabor 2. An optical light microscope, SEM and XRD analyses were used to conduct microstructural characterisation of the steel investigated. Electrochemical potentio-dynamic polarisation measurements were taken to evaluate corrosion behaviours of the examined steels. Wear tests were conducted in a pin-on-disc type wear device by using a load between 10 N and 60 N. While the corrosion resistance of the boronising heat treated steel deteriorated by the pitting damage mechanism within corrosive media, uniform corrosion damage enhanced the corrosion resistance of the examined boronised steel. Oxidative adhesion, cracking of oxide and/or boride layer, and severe plastic deformation mechanisms were dominant during the wear tests. Severe plastic deformation and cracking of the oxide and/or boride layer caused wear mechanism to transform from mild to severe.
Corrosion behaviours of high Cr-Ni cast steels in the HCl solution
(Elsevier Science Sa, 2010) Bulbul, Saban; Sun, Yavuz
In this study, the effect of composition and heat treatment (aging) on the corrosion resistance of high alloy steels containing 0.4% C, 29% Cr and 4-20% Ni has been investigated. Aging heat treatment was composed of quenching after holding at 1200 degrees C for 6 h and aging at 750 degrees C for 18 h. Corrosion tests were performed by suspending the samples of certain sizes into the 10% HCl solutions measuring the weight loss, and also by potentiodynamic polarization measurements in the same solution. The results of the corrosion tests revealed that, corrosion resistance of the aged alloys was increased with increasing Ni content. On the other hand, corrosion resistance of the austenitic matrix alloys was increased upon aging heat treatment while that of ferritic matrix alloy decreased with aging. (c) 2010 Elsevier B.V. All rights reserved.
Dry Sliding Wear Behavior of (MWCNT plus GNPs) Reinforced AZ91 Magnesium Matrix Hybrid Composites
(Korean Inst Metals Materials, 2020) Turan, Muhammet Emre; Zengin, Huseyin; Sun, Yavuz
This study aims to improve tribological performance of magnesium alloy with the addition of carbonaceous (C-based) reinforcements. Synergetic effects of MWCNT and GNPs on wear performance of AZ91 magnesium alloy was evaluated with this report. AZ91-0.3 wt% MWCNT and AZ91-0.15 wt% MWCNT-0.15 wt% GNPs hybrid composites were synthesized using hot pressing via semi powder metallurgy. Microstructures were examined by scanning electron microscope and x-ray diffraction test devices then hardness and wear tests were performed for all samples. Results clearly show that hardness and wear behaviors of AZ91 magnesium alloy were improved significantly with the addition of reinforcements. Uniform distribution of carbon atoms was achieved for both of two samples. AZ91-0.15 wt% MWCNT-0.15 wt% GNPs composite showed best wear performance among the specimens.
Effect of carbon content and drawing strain on the fatigue behavior of tire cord filaments
(Elsevier - Division Reed Elsevier India Pvt Ltd, 2018) Koymatcik, Huseyin; Ahlatci, Hayrettin; Sun, Yavuz; Turen, Yunus
In this work we aim to investigate fatigue strengths of the steel filaments in diameter of 0.25 mm with three different Carbon (0.70%C, 0.80%C and 0.90%C) and with four different drawing strains (3.25, 3.37, 3.71 and 3.76) by the pure bending test method. All fatigue tests have been carried out at room temperature and at a frequency of 10 Hz via a custom manufactured pure bending testing machine of which the fully reserved strain value, R = epsilon(min)/epsilon(max), is -1. The applied value of cyclic deformation, epsilon, has been chosen from the range 0.20%-1.07% as bending strain. The plots of S-N (Strain-Cycle) curves are based on high cycle fatigue (HCF) life is greater than or equal to 10(4) cycles. The fatigue deformation limit values have been determined as 0.55% units and 0.20% units for the steels of the 0.25NT-70C and 0.25UT-90C quality, respectively. The increase in hardness resulting from the microstructural thinning (due to drawing strain) increases the fatigue deformation limit of the steels containing 0.80%C. Despite the increase in the drawing strain, carbon content and hardness, the fatigue deformation limit decreased with increasing inclusion content. Fractured surfaces of the samples, which have been broken at both high fatigue life and fatigue deformation limit values, are inspected via SEM. The SEM inspection has demonstrated that the fatigue fracturing of the steel filaments are similar to that of baseball bat cracking. (C) 2018 Karabuk University. Publishing services by Elsevier B.V.
The effect of GNPs on wear and corrosion behaviors of pure magnesium
(Elsevier Science Sa, 2017) Turan, Muhammet Emre; Sun, Yavuz; Akgul, Yasin; Turen, Yunus; Ahlatci, Hayrettin
This study aims to investigate the role of graphene on wear and corrosion behaviors of pure magnesium. Magnesium/Graphene Nanoparticle (GNP) composites were fabricated via semi powder metallurgy method with a different content of graphene (0.1, 0.25 and 0.5 wt%). The effect of graphene in pure magnesium was examined by hardness, wear and corrosion tests. Microstructural and phase analysis were carried out by Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) analysis. Experimental results revealed that, hardness values increased with the addition of graphene. There was a same trend in wear behaviors with increase of graphene rate. The best wear performance was belonging to the 0.50 wt% graphene/mg composite under load of 10N. So improvement of wear properties was achieved using graphene as reinforcement. According to the microstructural evolution, the uniform distribution was achieved for all samples but partially agglomeration could be seen in Mg-0.50 wt% graphene. Compared to the pure magnesium, corrosion performance was affected negatively in graphene reinforced composites. (C) 2017 Elsevier B.V. All rights reserved.
The effect of graphene-nanoplatelet and nano-teflon on mechanical properties of UV photo-resin 3D printer products
(Taylor & Francis Inc, 2022) Karaca, Tunahan Hakki; Cicek, Bunyamin; Aydogmus, Tuna; Sun, Yavuz
In this study, a photo-resin 3D printer was used as an example of the additive manufacturing method. The aim of the study is to improve the mechanical values of resin printer products. For this purpose, the change of mechanical values with the effect of nanostructures added to the resin by a special mixing method was investigated. Micro images, surface quality, and layers of the products were analyzed by scanning electron microscope (SEM). Compression, tensile and impact tests were applied for mechanical values. Nano-graphene changed the mechanical values to negative. The nano Teflon addition showed an improvement of about 35%.
The effect of head hardening process on the residual stress of rails
(Sage Publications Ltd, 2018) Turan, Muhammet E.; Ozcelik, Sait; Husem, Fazil; Ahlatci, Hayrettin; Sun, Yavuz; Tozlu, Ibrahim
In this study, the head hardening process was employed, by using a mixture of air and water under laboratory conditions, to improve the residual stress behavior of R260 grade rails . For this purpose, three types of specimens were selected. One group of rails was heated up to the austenite stage and then cooled for 20 s; the next group was heated up to the austenite stage and then cooled for 40 s and the third group was not exposed to any heat treatment. The hardness results showed that the specimens cooled for 40 s had excessive hardness; the specimens cooled for 20 s exhibited similar properties as that of R350HT rail standards, which are especially preferred in the lower radius of curvature bends in railways, but not that of R260. According to the analysis of residual stress, all samples had compressive residual stress, but the specimens cooled for 20 s had the highest stress value.
EFFECT OF INDIUM ADDITION ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AS-CAST AND HOT-ROLLED AM60 MAGNESIUM ALLOY
(Tanger Ltd, 2017) Zengin, Huseyin; Turen, Yunus; Ahlatci, Hayrettin; Sun, Yavuz
In this study, effect of indium (In) addition on microstructure and mechanical properties of AM60 magnesium alloys was investigated. In additions were made by 0.2, 0.5 and 1 wt.%. Alloys were produced by conventional gravity casting in a steel mould. A homogenization treatment at 350 degrees C for 24 h was performed after casting processes. Homogenized samples were 1 pass hot-rolled by 40 % thickness reduction at 350 degrees C. The results showed that the average grain size of as-cast and hot-rolled AM60 alloys decreased with In addition. SEM analysis revealed that In addition led to formation of tiny Mg-In binary second phases at triple junctions. Tensile strength of as-cast AM60 alloy increased with increasing amount of In up to 0.5 wt.% above which it decreased. However, after hot-rolling process, AM60 alloy containing 0.2 wt.% In showed the best tensile properties. These improvements were attributed to the refinement of microstructure and dispersion strengthening by Mg In intermetallic phases.
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; Topcu, Ismail; 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.
The Effect of Ti Addition and Aging on Wear Behavior of AlMgSi Alloys Reinforced with In Situ Al3Ti Particles
(Springer, 2013) Sun, Yavuz
The purpose of this study is to investigate the effects of Ti addition (1 and 2% Ti) and aging heat treatment on the mechanical and wear characteristics of Al-12Si-20Mg cast alloys. In preliminary studies conducted to determine the aging parameters, cast alloys were kept at 550 A degrees C for 2 h before being quenched into water and aged at 200 A degrees C for five different periods (3, 6, 9, 12, and 15 h). As the specimen aged for 12 h had the highest hardness value, all the specimens were aged at 200 A degrees C for 12 h. The microstructures of the as-cast and aged specimens were analyzed using an optical microscope and a scanning electron microscope. The hardness of the investigated alloys was measured by micro-hardness test. The wear tests were carried out using the pin-on-disk model wear test apparatus, and the results were evaluated according to weight loss. According to the wear test results, the wear behavior of the investigated alloys changed depending on the aging heat treatment applied and the load. While Ti addition and the aging heat treatment applied reduce the weight loss at low loads (5 N), they increase the weight loss at higher loads (10 and 20 N).
The Effect of TiB2 Content on Wear and Mechanical Behavior of AZ91 Magnesium Matrix Composites Produced by Powder Metallurgy
(Springer, 2019) Aydin, Fatih; Sun, Yavuz; Turan, M. Emre
In this research, AZ91 magnesium matrix composites reinforced with three weight fractions (10, 20, and 30 wt.%) of TiB2 particulates were fabricated by powder metallurgy using hot pressing technique. The microstructure, density, hardness, wear, and mechanical properties of the specimens were investigated. Microstructure studies showed that fairly uniform distribution of reinforcements was achieved, but partial agglomeration could be clearly seen at 30 wt.% TiB2. X-ray studies exhibited that phases of Mg, Mg17Al12, and TiB2 were found. As compared to AZ91, the hardness and wear resistance considerably increased with increasing reinforcement content. The presence of TiB2 particles improved 0.2% compressive yield strength and ultimate compressive strength (UCS); however, UCS decreased above 20 wt.% TiB2. Wear mechanisms are oxidative and abrasive.
Effect of Zn addition on mechanical and corrosion properties of as-cast and as-extruded WE43 magnesium alloys
(Iop Publishing Ltd, 2019) Subasi, Yasin; Turen, Yunus; Zengin, Huseyin; Ahlatci, Hayrettin; Sun, Yavuz
In this study, the microstructure, mechanical properties and corrosion resistance of as-cast and as-extruded WE43-xZn (x;=;0, 0.5, 1.0 wt%) magnesium alloys were investigated. The microstructure of the as-cast alloys showed that the WE43-xZn alloys contained Mg41Nd5 and Mg24Y5 intermetallic compounds. Besides, LPSO (Long-period stacking ordered) type Zn-rich phases were also originated in the microstructure with increasing Zn content. Furthermore, LPSO structure was observed both in the ?-Mg grain and at the grain boundaries in Zn-containing WE43 alloys. The Vickers hardness values increased by the raising Zn content in the as-cast, solution treated and as-extruded WE43-xZn alloys. It was observed that yield strength (YS) increased gradually by the addition of Zn content, but 0.5 wt% Zn addition to as-cast WE43 alloy resulted in much more improvements on the ultimate tensile strength (UTS) and elongation % (EL) values compared to as-cast WE43-1.0Zn alloy. It was seen that mechanical properties improved with increasing Zn content for the as-extruded alloys. The as-cast specimens showed that corrosion resistance improved by increasing Zn content due to the presence of LPSO structures, but in the extruded alloys it varied in relation to the presence and distribution of second phases and also the morfologies of LPSO structures.
Effects of alloying element and cooling rate on properties of AM60 Mg alloy
(Iop Publishing Ltd, 2019) Elen, Levent; Cicek, Bunyamin; Koc, Erkan; Turen, Yunus; Sun, Yavuz; Ahlatci, Hayrettin
Magnesium and its alloys have become important structural materials in the last couple of decades due to their exceptional and mechanical properties. In this study, the effects of the introduction Cd, Bi, and Sn alloying elements were introduced into AM60 alloys produced from Mg-Al-Mn triple junction in order to improve the microstructural and mechanical properties. The weight percent of the alloying elements was chosen as 0.5% wt besides the introduction of the additional alloying elements, the effect of cooling rate on microstructural and mechanical properties of the alloys have been investigated. The results showed that the alloying elements introduced to AM60 resulted in an improvement in the mechanical properties of the alloys, which is attributed to the changes in the microstructure. The higher cooling rate led to the formation of the finer a-Mg master matrix which in turn enhanced the mechanical properties of the alloys. It was observed that the intermetallic phase of beta-Mg17Al12 at the grain boundaries became thinner due to the rapid cooling rate and the introduction of the alloying elements, and the continuity decreased and the intergranular distance shortened. The addition of the alloying element increased the tensile strength of the AM60 alloy from 140 MPa to 210 MPa and the elongation values increased from 5% to 22%. The effects of the alloying elements and the cooling rate on the hardness and yields properties of the samples were also studied.
EFFECTS OF BISMUTH (BI) ADDITIONS ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AZ91 ALLOY
(Tanger Ltd, 2015) Elen, Levent; Zengin, Huseyin; Turen, Yunus; Turan, Muhammet Emre; Sun, Yavuz; Ahlatci, Hayrettin
In this study, the effects of bismuth additions of 0.2, 0.5 and 1 wt% on microstructure and mechanical properties of AZ91 alloy were examined. A permanent mold casting procedure was carried out to produce the alloy billets under a mixed gas atmosphere of SF6 and CO2. Microstructural investigations showed that Mg3Bi2 intermetallic phases were formed in all the samples and it coarsened with increasing amount of Bi in AZ91 alloy. Furthermore, a finer dispersion of Mg17Al12 intermetallic phases was observed in the structures as the amount of Bi in AZ91 increased. It was also showed that increasing Bi addition increased the hardness of AZ91 alloy. However, the highest hardness value was found for the alloy having 0.5wt% Bi addition that means high amount of Bi can decrease the hardness of AZ91 alloy. On the other, there were no considerable changes in the tensile strengths and yield strengths of the alloys as the amount of Bi increased although a slight increase in both strengths were observed with increasing amount of Bi. Percent elongation at break showed a decrease as Bi addition increased.
Effects of carbonaceous reinforcements on microstructure and corrosion properties of magnesium matrix composites
(Elsevier Science Sa, 2018) Turan, Muhammet Emre; Sun, Yavuz; Aydin, Fatih; Zengin, Huseyin; Turen, Yunus; Ahlatci, Hayrettin
In this study carbonaceous (C-based) reinforced AZ91 matrix composites were fabricated with the same weight fraction of 0.50 wt.% via semi powder metallurgy. The hot pressing test machine was used under high purity argon atmosphere. Multi-wall carbon nanotube (MWCNT), Graphene Nanoplatelets (GNPs) and Fullerene (C60) were used as reinforcements. Microstructure, hardness and corrosion performances of fabricated composites were investigated. Results show that hardness of AZ91 alloy was improved with the addition of carbonaceous reinforcements. AZ91/C60 composite exhibited highest hardness performance. However, corrosion performance of AZ91 was affected negatively by the addition of reinforcements. MWCNT exhibited highest corrosion rate among the fabricated samples.
Evaluation of thermal conductivity of GNPs-doped B4C/Al-Si composites in terms of interface interaction and electron mobility
(Elsevier Science Sa, 2019) Polat, Safa; Sun, Yavuz; Cevik, Engin; Colijn, Hendrik
The examination of the interactions between graphene and other components commonly used in thermal applications is an important approach for the development of materials with high thermal conductivity. For this purpose, graphene-doped boron carbide reinforced Al Si matrix composites were produced using semi-powder and pressure infiltration methods together. These composites were then characterized by SEM, TEM and XRD analysis. Thermal conductivity coefficients of these composites were determined experimentally by Laser Flash method. In order to examine the effect of phonon transfer on the experimental data, the interacting components were simulated, and the interfacial thermal conductivity was calculated with the acoustic mismatch model. Then, theoretical thermal conductivity of composites was calculated by Hasselman-Johnson model and Maxwell's approach. The electrical conductivity of the composites was measured by four-point probe method for electron mobility. As a result, experimental results were found to be slightly lower than the theoretical ones. This was affected by several different factors but the most important one is thought to be related to porosity.

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