Browsing by Author "Ayvaz, M"
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Item Microstructural, mechanical, wear and corrosion properties of Mg3Zn/ TiB2-CNT nanocompositesÖzer, E; Ayvaz, M; Zalaoglu, D; Übeyli, M; Özdogru, TLight magnesium nanocomposites, offering great weight savings, have a great potential to be utilized in aerospace and automotive industries. They have also been attracted much attention to be evaluated as biomaterial recently owing to their in vitro biodegradability and biocompatibility properties. In the present research, the Mg3Zn/TiB2-CNT nanocomposites were successfully manufactured using mechanical alloying, cold compaction at 600 MPa and finally sintering at 560 degrees C for 1 h. Their microstructural, mechanical, wear and corrosion properties were investigated extensively for comparison with the Mg3Zn alloy. It was found that the microhardness of the Mg3Zn nanocomposites increased directly with the hybrid reinforcement ratio. In parallel to the hardness, an addition of 15 vol % TiB2-CNT reinforcement to the Mg3Zn alloy allowed to the improvement of the compressive strength by of 46.3 % at a reasonable ductility level of similar to 7.8 % compared to the Mg3Zn alloy. The crystallite size, decreasing with an augmentation in the reinforcement content steadily, was obtained to be smaller than 100 nm for the bulk Mg3Zn nanocomposites. Moreover, the wear loss of Mg3Zn alloy reduced by similar to 45 % upon the incorporation of 15 % hybrid reinforcement due to the occurrence of a stable tribolayer between the working couple. An additional benefit of the incorporation of hybrid reinforcement into Mg3Zn alloy was also obtained in the progress of corrosion resistance significantly. The corrosion rate was recorded to be 1462.6 mpy for Mg3Zn but it decreased to 276 mpy upon the incorporation of 10 % hybrid reinforcement into the alloy.Item Microstructural properties and tribological behaviours of Ultra-High frequency induction rapid sintered Al-WC compositesÇavdar, U; Gezici, LU; Gül, B; Ayvaz, MIn this study, sinterability of 1, 3, 5, 9 and 15 wt.% WC reinforced aluminum matrix composite samples by induction fast and conventional sintering methods was investigated. For this purpose, firstly, it was pressed by unaxial cold pressing method under 200 MPa pressure. Some of these raw samples were sintered by ultra-high frequency induction fast sintering method at 600 degrees C temperature for 300 sec., while the other part of the samples were sintered by 600 degrees C for 1800 sec. The density and hardness values of sintered composite samples were measured and microstructural properties, abrasion and friction behaviours were investigated. In this study, it was seen that increased WC reinforcement ratio and abrasion resistance and friction coefficient increased together. In addition, this study showed that ultra-high frequency sintering is as successful as traditional method in Al-WC composite production.Item Effect of Heat Treatment and Reinforcement Content on the Wear Behavior of Al-4Cu/Al2O3-CNT NanocompositesÖzer, E; Ayvaz, M; Übeyli, M; Sarpkaya, IIn the study, the effects of hybrid reinforcement (nano-alumina and MWCNT) and heat treatment on the wear behavior of the Al-4Cu nanocomposites were investigated under dry sliding condition against W-6Co ball by means of a ball-on-disk type tribometer. The load and the sliding speed were kept constant and selected to be 10 N and 0.1 m s(-1), respectively, in the course of the wear tests. Meanwhile, the wear tests were completed after a total sliding distance of 1500 m was reached for each case. During these tests, the wear loss of the nanocomposites was measured at every 250 m. The worn surfaces of the nanocomposites were examined with the help of stereo and scanning electron microscopes. The volumetric wear rates, wear coefficients and wear mechanisms were identified for the nanocomposites to clarify the influence of reinforcement content and heat treatment on their wear resistance. The volume loss at the wear distance of 1500 m was obtained as 24.9 and 8.2 mm(3) for the annealed and aged Al-4Cu alloy, respectively. On the other hand, it decreased to 4.6 and 3.2 mm(3) in the case of the nanocomposites with 15% hybrid reinforcement in the annealed and aged conditions, successively. Moreover, increasing the hybrid reinforcement amount decreased the wear loss of the aged nanocomposites substantially in such a way that it resulted in the mild wear.Item Properties of Aluminum Nano Composites Bearing Alumina Particles and Multiwall Carbon Nanotubes Manufactured by Mechanical Alloying and Microwave SinteringÖzer, E; Ayvaz, M; Übeyli, M; Sarpkaya, IIn this research, the effects of heat treatment and hybrid reinforcement ratio on the microstructural and mechanical properties of Al-4Cu nanocomposites containing MWCNT and nano Al2O3p were investigated. First of all, the hybrid reinforced Al-4Cu nanocomposites were manufactured with the aid of mechanical alloying and microwave sintering. And then, they were subjected to various heat treatments; annealing and artificial aging at 170, 180 and 200 degrees C individually. After that, the microstructural observations were made using X-ray diffraction, optical microscope and scanning electron microscopes (SEMs). The secondary electrons (SE), back scattered electrons (BSE), energy dispersive X-ray (EDX) and elemental mapping analyses of the specimens were carried out with the aid of SEMs. In addition, the nanoindentation tests were done to get the nanohardness and elastic modulus of composites. Finally, the composites were subjected to the compression test to clarify their compressive properties. The Al2Cu and Al4C3 precipitates were detected in the composite samples either annealed or peak-aged at 200 degrees C, while the intermetallic compound, Al7Cu2Fe, precipitated only in the aged samples. A significant increment in the nanohardness of composites was obtained with increasing reinforcement content. Moreover, the elastic modulus of annealed and peak-aged composites, reinforced with 15% hybrid reinforcement in volume, increased by 59% and 57%, respectively compared to the unreinforced alloy. Furthermore, the use of hybrid reinforcement in the alloy matrix allowed an improvement of compressive yield strength at the expense of compressive strain.Item Investigation of mechanical and tribological behavior of SiC and B4C reinforced Al-Zn-Mg-Si-Cu alloy matrix surface composites fabricated via friction stir processingAyvaz, SI; Arslan, D; Ayvaz, MIn this study, SiC and B4C reinforced Al-Zn-Mg-Si-Cu alloy matrix surface composites (SCs) were produced by friction stir processing (FSP) technique. Microstructural, mechanical, and tribological properties of produced SCs, and those of non-reinforced samples were examined. In B4C and SiC reinforced SCs fabricated by friction stir processing, approximately a 20% increase in hardness was achieved as compared to the base metal. The maximum microhardness values of B4C and SiC reinforced surface composites were determined as 88.1 and 89.7 HV, respectively. The tensile strengths of these samples were measured as 166.42 and 174.74 N.mm(-2), respectively. As a result of the tests performed under 3, 5, and 10 N applied loads, it was observed that the friction coefficient decreased in general with the applied load. A higher coefficient of friction was obtained in SiC reinforced SCs than those of B4C reinforced SCs and non-reinforced samples. It was determined that the wear rate of B4C reinforced SCs decreased by similar to 30-40% and SiC reinforced SCs by similar to 50-55% compared to non-reinforced samples. In the examinations, it was revealed that mechanically mixed layer formation effectively reduced wear rate in these samples compared to non-reinforced samples.Item Dry tribological behaviour of microwave-assisted sintered AA2024 matrix hybrid composites reinforced by TiC/B4C/nano-graphite particlesÖzer, E; Ayvaz, MThis study aimed to produce hybrid composites with a AA2024 matrix reinforced by TiC/B4C/nano-graphite through a microwave-assisted sintering technique at 560 degrees C for 60 min. The nano-graphite ratio in the produced composite samples was kept constant as 1 wt%. TiC and B4C were used in equal ratios at 2, 6 and 10 % by weight total to determine their effects on tribological properties. Wear tests were conducted under three different loads: 3, 5 and 10 N. In the hybrid composites produced, an inverse correlation was observed between the increase in reinforcement ratio and sinterability, while a direct correlation relationship was found in hardness and wear resistance. Compared to the sample containing 2 % TiC/B4C in total by weight, a similar to 50 % increase in Brinell hardness and a 52-68 % decrease in wear rate was obtained in the sample containing 10 % TiC/B4C. As the reinforcement ratio increased, tribofilm formation increased, and abrasive wear was replaced by mild-oxidative wear type.Item The ballistic behavior of type 1 metallic pressurized hydrogen storage tanks against ballistic threatsKural, S; Ayvaz, MToday, increasing energy demand and human consumption are becoming increasingly important for the safe use, storage and transport of energy resources. Energy sources have been the target of increasing terrorism and wars since the 20th century. In the future, alternative energy sources, such as hydrogen energy, are expected to take the place of fossil energy resources. This means that ballistic threats will target these resources. In this study, for the first time in the literature, the ballistic behavior of Type 1 metallic pressurized hydrogen storage tanks made of the 6061 T6 aluminum and SS304 stainless steel alloys at the different thicknesses against 7.62 mm were investigated under usage pressure. For these alloys, the minimum safe wall thickness of the hydrogen tank is mathematically calculated using finite element analysis. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Item Microstructure and Dry Sliding Wear Behaviors of Microwave-Sintered Al-4.4Cu-0.7 Mg-0.6Si-B4C/nGr Hybrid CompositesAyvaz, MIn recent years, more advanced mechanical and tribological properties have been needed in aluminum matrix composites due to the increasing variety of applications. For this purpose, second-generation aluminum matrix hybrid composites that have two or more different particle reinforcements are being developed today. In this study, in order to improve tribological and microstructural properties, nano-sized graphite and B4C-reinforced Al-4.4Cu-0.7 Mg-0.6Si aluminum alloy hybrid composites were produced. As a sintering method, the microwave sintering technique, which is one of the fast sintering methods, was preferred to prevent and/or minimize the formation of unwanted reaction products. In Al-4.4Cu-0.7 Mg-0.6Si-B4C/nGr hybrid composites, 4 different (3, 6, 9 and 12 wt %) B4C and 1 wt % nGr reinforcements were used. Raw samples, compressed by the one-way cold pressing method under 600 MPa pressure, were sintered in the microwave oven at 550 degrees C temperature for 60 min. In XRD analyses, whereas any unwanted reaction product (Al4C3, Al3BC, etc.) was not detected, theta-Al2Cu precipitate formations were detected. In hybrid composites where no graphite agglomeration was observed within the matrix, the highest hardness value (103.9 H-v0.05) was determined in the sample containing 6 wt % B4C and the lowest specific wear rate (0.271 x 10(-3) mm(3)/Nm) was determined in the sample containing 12 wt % B4C.Item Characterization and Tribological Properties of Novel AlCu4.5SiMg Alloy-(B4C/TiO2/nGr) Quaternary Hybrid Composites Sintered via MicrowaveAyvaz, MIn the future, hybrid aluminum matrix composites, which are the second generation composites, will be replaced by solid reinforced third-generation quaternary hybrid composites in which nano- and micro-scale reinforcement particles are used together. In this study, microwave sinterability of B4C, TiO2 (nm + mu m), and nGr reinforced quaternary hybrid composites that had AlCu4.5SiMg alloyed Matrix, and their microstructural and tribological properties after sintering were examined. The proportion of nGr in the composite sample was taken as 0.5 wt%, while B4C and TiO2 were used in three different proportions (3, 9, 12 wt%). After being compressed under 600 MPa pressure, the composite samples were sintered for 60 min at 550 degrees C by a microwave oven with a power of 2.9 kW and a frequency of 2.45 GHz. It was determined that due to its high microwave absorbency, B4C reinforcement improved the microwave sinterability more compared to TiO2. In XRD analyses, whereas Al4C3 and Al3BC reaction products were not seen as harmful, the intermetallic phase of Al2Cu was detected. It was determined that both friction coefficient and wear resistance increased as the proportion of B4C increased in composite samples. In AlCu4.5SiMg-(12 wt% B4C/3 wt% TiO2/0.5 wt% nGr) quaternary hybrid composites with the highest hardness (97.6 HV), the lowest specific wear rate (0.118 mm(3) Nm x 10(-3)) was detected. [GRAPHICS] .Item The Effect of Aging Parameters and Roughness on the Wear Properties of Aluminum Alloy 6082Cetinel, H; Ayvaz, MThe aim of this study was to investigate the influence of aging parameters and initial roughness on the wear properties of the aluminum alloy AA 6082 (Al-Mg-Si). For this purpose, various heat treatments were carried out. Afterwards, the solutionized samples and artificially aged samples (at 185 degrees C for 3 and 6 h) were prepared in terms of two different average surface roughnesses via various grades of grinding. The wear behavior of the samples was investigated by a pin-on-disc wear test apparatus under four different applied loads (5, 10, 15 and 20 N) and five different sliding distances (250, 500, 750, 1000, 1250 and 1500 m). The sliding velocity was 30 cm x s(-1). After the wear tests, the mass loss was measured for all samples and the worn surfaces were examined by scanning electron microscopy (SEM). The wear test results clearly show that with increasing hardness, the mass loss decreases, and the mass loss of the worn surfaces increases with increasing sliding distance, test load and initial roughness.Item A novel method for determining effects of fire damage on the safety of the Type I pressure hydrogen storage tanksAyvaz, M; Ayvaz, SI; Aydin, IConsumption of the fossil fuels causes greenhouse gas effect and environmental pollution, which are two basic problems of our age. As a result of this problem, clean and renewable alternative energy sources are beginning to replace fossil fuels. Nowadays, the use of hydrogen energy, which is one of the clean energy, is increasing in transportation and industrial areas. Increasing of hydrogen energy usage, scientists are attempting to solve the many safety problems (such as fire, burst, impact and hydrogen embrittlement) that can occur during the storage and consumption of hydrogen energy. In this study, during the event of fire, the safety of metallic Type I pressure hydrogen storage tanks is investigated by using a novel approach. In this new approach, the mechanical strength drops of the tank materials that is related with temperature rising are added to the safety calculations. In the study, 6061 T6 aluminum and SS 316L stainless steel alloys were used as hydrogen tank material. The safety of hydrogen tanks modelled using these alloys was investigated under different temperature conditions (22, 100, 200 and 300 degrees C) and internal pressure (15, 20 and 25 MPa). (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Item Mechanical properties of Al-Cu/B4C and Al-Mg/B4C metal matrix compositesAyvaz, M; Cetinel, HTo be able to successfully produce ceramic-reinforced aluminum matrix composites by using the powder metallurgy method, the wetting of ceramic reinforcements should be increased. In addition, the negative effects of the oxide layer of the aluminum matrix on sinterability should be minimized. In order to break the oxide layer, the deoxidation property of Mg can be used. Furthermore, by creating a liquid phase, both wettability and sinterability can be improved. In this study, the effects of Mg and Cu alloy elements and sintering phase on the wettability, sinterability, and mechanical properties of Al/B4C composites were investigated. For this purpose, various amounts (5, 10, 20, and 30 wt.-%) of B4C reinforced Al5Cu and Al5Mg matrix composites were produced by the powder metallurgy method. After pressing under 400 MPa pressure, composite samples were sintered for 4 hours. The sintering was carried out in two different groups as solid phase sintering at 560 degrees C and liquid phase sintering at 610 degrees C. Despite the deoxidation effect of Mg in Al5Mg matrix composites, higher mechanical properties were determined in Al5Cu composites which were sintered in liquid phase because wettability increased. The highest mechanical properties were obtained in the 20 wt.-% B4C reinforced Al5Cu sample sintered in liquid phase.Item Ballistic performance of powder metal Al5Cu-B4C composite as monolithic and laminated armorAyvaz, M; Cetinel, HIn this study, ballistic performances of x wt.-% B4C (x = 5, 10, and 20) reinforced Al5Cu matrix composite samples were investigated as a monolithic and laminated composite armor component. Composite armor plates were produced by the powder metallurgy method. The prepared powders were pressed under 400 MPa pressing pressure. Green compacts were pre-sintered at 400 degrees C for 30 minutes in order to blow the lubricant. Subsequently, liquid phase sintering was performed at 610 degrees C for 210 minutes. In ballistic tests, 7.62 mm caliber armor-piercing bullets were used as the ballistic threat. In the ballistic tests of monolithic armors, only 10 mm thick powder metal composite plates were tested. In the ballistic tests of laminated composite armors, these powdered metal plates were layered with 10 mm thick alumina ceramic plate front layers and 10 mm thick AA5083 plates. Although all of the monolithic powder metal composite armors were penetrated, they showed multi-hit capability. All of the laminated composite armors provided full ballistic protection. It was determined that with the increase in B4C reinforcement rate, the ballistic resistance also increased due to the improvement in strength, hardness, and abrasive feature.