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Öğe Effect of Milling Time on Dry Sliding Wear Behaviors of Carbon Nanotubes Reinforced Al Matrix Composites(Amer Scientific Publishers, 2020) Yildirim, Musa; Ozyurek, Dursun; Guru, MetinIn this study, the effect of mechanical milling time on microstructure, hardness and dry sliding wear behaviors of carbon nanotube reinforced aluminum matrix composites was investigated. Multi-walled carbon nanotubes (amount of 1%) were added to gas atomized AA7075 alloy as a reinforcement material and it was mechanical milled five different times. Milled Al-CNTs composite powders were added in a steel mold and pre-formed by cold pressing and hot pressing. Pre-formed composites samples were sintered. Microstructures of produced samples were examined by Scanning electron microscope. Density and hardness values were measured 1 ms(-1) sliding speed, 30 N loads and five different sliding distances were used in dry sliding wear tests on pin on disc type wear apparatus. As a result of the studies, it was found that the particle size increased as the milling time increased. Powders milled for 100 min had the largest particle size, whereas powders milled for 120 min had a smaller particle size. The results indicated that composites mechanically milled for 120 min had both the highest hardness value and the lowest weight loss.Öğe The effects of Mg amount on the microstructure and mechanical properties of Al-Si-Mg alloys(Elsevier Sci Ltd, 2013) Yildirim, Musa; Ozyurek, DursunIn this study, the effects of magnesium (Mg) addition to A356 aluminum alloy at different amounts on the microstructure and mechanical properties of this alloy were examined. For the experimental studies, three different alloys (0.43, 0.67 and 0.86 wt%) having various amounts of Mg were prepared through casting process in the form of plates. The plates were homogenized and cooled in the furnace. All the samples were treated with aging process (T6) and then tensile samples were prepared from the homogenized samples. The samples treated with T6 process were characterized by optical microscopy, laser confocal microscopy, Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) and X-Ray Diffraction (XRD) examinations as well as hardness measurements and tensile tests. The phases which were formed in the microstructures for different amounts of Mg were examined. It was observed that iron-rich intermetallic compounds were also formed in addition to the phases resulting from the aging process. Fe-rich intermetallic compounds, observed from the fracture surfaces, were found to reduce the tensile strength the alloy. The results also indicate that the tensile strength and hardness of the alloy increase with increasing Mg amount. (C) 2013 Elsevier Ltd. All rights reserved.Öğe The Effects of Molding Materials on Microstructure and Wear Behavior of A356 Alloy(Walter De Gruyter Gmbh, 2017) Yildirim, Musa; Ozyurek, Dursun; Tuncay, TanselIn this study, the effect of molding materials on microstructure and wear behavior of A356 alloy was investigated. Different microstructures were obtained by casting A356 alloy into the molds made from three different materials. Homogenization and aging heat treatments were applied as cast blocks. The aged samples were tested by pin-on-disk-type standard wear equipment. The results showed that casting into different mold materials resulted in different microstructures of A356 alloy. Microstructures of the Al-Si-Mg alloy differ depending on the mold materials. Secondary dendrite arm space (SDAS) decreased proportionally with increasing cooling rate. Based on the cooling rate, hardness values of the alloy also differ. As the cooling rate increased, hardness of the alloy increased. The SDAS increased due to the decreasing cooling rate. In wear tests, increasing weight loss was observed with decreasing cooling rate.Öğe The Effects of Precipitate Size on the Hardness and Wear Behaviors of Aged 7075 Aluminum Alloys Produced by Powder Metallurgy Route(Springer Heidelberg, 2016) Yildirim, Musa; Ozyurek, Dursun; Guru, MetinIn this study, the effects of precipitate size, which occurred on the microstructure by applying T6 heat treatment at different temperatures and different time intervals, were investigated on hardness and wear behaviors of 7075 Aluminum alloys produced by powder metallurgy route. Aging heat treatments were performed at three different temperatures (110-130 A degrees C) and four different times (16-28 h). The results show that MgZn2 precipitates were formed in the microstructure by aging heat treatments and their sizes were changed depending on aging temperature and time. The precipitate size was increased by increasing aging temperature and time. The largest size of the precipitate was measured from SEM images of the samples aged at 130 A degrees C for 24 h. The highest hardness values were measured at 120 A degrees C for 24-h aged samples. The wear test results revealed that the weight loss was increased with increase in sliding distance and the minimum weight loss was observed at 120 A degrees C for 24-h aged samples.Öğe Experimental investigation and prediction of wear properties of Al/SiC metal matrix composites produced by thixomoulding method using Artificial Neural Networks(Elsevier Sci Ltd, 2014) Ozyurek, Dursun; Kalyon, Ali; Yildirim, Musa; Tuncay, Tansel; Ciftci, IbrahimIn this study, the wear properties of the SiC particle reinforced aluminium (A356) composite materials (MMCs), produced with thixomoulding method, were investigated both by experimental and Artificial Neural Network (ANN) model in order to determine the weight loss after the wear tests. Two different temperatures (590 degrees C and 600 degrees C) were used in production of the MMCs containing 5%, 10%, 15% and 20% SiC (vol%). The samples of MMC were tested at 2 ms (1) constant sliding speed under 30 N and 60 N loads against four different sliding distances (500 m, 1000 m, 1500 m, and 2000 m). The results indicated that by increasing the production temperature increased the grain size of the MMCs was increased, but the hardness was decreased. The MMCs produced at 590 degrees C were found to have lower weight loss as compared with ones produced at 600 degrees C. In the theoretical prediction model of the MMCs, weight loss, SiC per cent, production temperature, applied weight and sliding distance were used as input values. After comparing the experimental results and the ANNs predicted data it was observed that R-2 was 0.9855. This shows that the developed prediction model has a high level of reliability. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Investigation of microstructure and wear behaviors of al matrix composites reinforced by carbon nanotube(Taylor & Francis Inc, 2016) Yildirim, Musa; Ozyurek, Dursun; Guru, MetinIn this study, the effect of CNT amount in Al-CNT composites produced by adding carbon nanotube (CNT) to 7075 Al alloy in various amounts on microstructure and wear behaviors of aluminum matrix composites was investigated. CNT was added to 7075 Al alloy powder at five different amounts. The powders were mechanically milled for 2 hours. Mechanical milled powders were cold pressed and then pre-shaped by hot pressing. Pre-shaped samples were sintered for 1 hour under 10(6) millibar in 580 degrees C. Microstructure examinations, hardness measurements, and wear tests were carried out. The results show that CNT's in the microstructure were agglomerated as nanotube amount increases and there was no uniform distribution. The highest hardness value was obtained in AMC reinforced with 1% CNT while it is seen that hardness of the composite decreases and weight loss increases as CNT amount increases.Öğe An Investigation of Wear Behaviors of AA7075 Al Hybrid Composites(Walter De Gruyter Gmbh, 2018) Yildirim, Musa; Ozyurek, DursunThis study investigates the wear behavior of Al hybrid composites produced by adding 4% Ti and different amounts of B4C (ex situ) to the AA7075 alloy produced by powder metallurgy method in order to obtain TiAl3 (in situ) reinforcement phase. Different amounts of B4C (3%, 6% and 9 %) were added to the 4% Ti added AA7075 alloy. Preformed parts were sintered in controlled atmosphere (argon) heat treatment furnace at 580 degrees C for 4 hours and then cooled. After the sintering process, the samples were characterized with scanning electron microscopy, X-ray diffraction and density and hardness measurements. Wear tests of the samples were conducted at 1ms(-1) sliding speed, under 30N load for 6 different sliding distances (500-3000 m). As a result of the study, the density of the AA7075 alloys, added 4% Ti and different amounts of B4C, was observed to decrease by the increasing amount of reinforcement elements. Also, the highest hardness value was measured for the 9% B4C added AA7075 alloy. Wear test results showed that the weight loss of the aluminum hybrid composites increased with the increasing sliding distance. On the other hand, it was observed that weight losses of composites decreased with increasing amount of B4C.Öğe Investigation of Wear Behaviors of SiO2 Reinforced Aluminium Composites Produced by Pressureless Infiltration Method(Gazi Univ, 2019) Simsek, Ijlal; Yildirim, Musa; Ozyurek, Dursun; Simsek, DoganIn this study, the wear behaviors of SiO2 reinforced AA7075 matrix composites produced by pressureless infiltration method were investigated in the scope of the work, 10%, 20%, 30%, and 40% SiO2 were added into AA7075 Al alloy and produced by infiltration method. Produced samples' density values were measured by Archiment method, hardness values were measured in micro hardness device under 2 N load. Wear tests were performed using 1 ms(-1) sliding speed at five difference sliding distance under 15 N load by pin-on-disc type apparatus. As a result of the study, the density values were decreased by increasing SiO2 amount and hardness values were increased by increasing SiO2 amount. In addition the weight loss and friction coefficient were decreased depending on increasing of SiO2 amount.Öğe Microstructure, Hardness, Wear Behaviours of A356/Fly Ash Composites Fabricated by Powder Metallurgy Method(Springer India, 2022) Yildirim, Musa; Solakoglu, SimgeIn this study, we investigated the microstructure and wear behaviour of A356/fly ash composites fabricated using the powder metallurgy method. Fly ash was added to A356 Al alloy in four different ratios by weight and mechanically milled for 1 h. The milled composite powders were pre-formed under 800 MPa pressure and sintered for 1 h under vacuum at 590 degrees C. The microstructures of the produced samples were examined by optical microscope, SEM, EDS and XRD. The hardness measurements and wear tests were performed to determine the effect of fly ash content on the properties of the samples. As a result of the study, it was found that the hardness value increased with the increasing fly ash amount up to 2 wt% and decreased after 2 wt%. The wear test results were consistent with the hardness results. The maximum weight loss occurred in the composite containing 4 wt% fly ash.Öğe The tribological properties of A356-SiCp metal-matrix composites fabricated by thixomoulding technique(Walter De Gruyter & Co, 2012) Ozyurek, Dursun; Yildirim, Musa; Ciftci, IbrahimIn this study, A356-SiCp metal-matrix composites were produced through thixomoulding process, and these composites were subjected to wear tests. The composites containing various volume fractions of SiCp particles (5%, 10%, 15% and 20%) as the reinforcement were produced at two different temperatures of 590 degrees C and 600 degrees C. The influences of processing temperatures and reinforcement ratio on the properties and wear behaviour of the composites were investigated. Prior to the wear tests, microstructural properties and hardness of the composites were determined. For the wear tests, a pin-on-disc-type wear apparatus was employed to carry out the wear tests. The wear tests were carried out at 2.0 m/s sliding speed under 15 N load and for four different sliding distances. A scanning electron microscope (SEM) was used to examine the wear mechanisms on the worn surfaces of the composites. The results indicated that sphericity rate and hardness of the composites produced at 590 degrees C were higher than those of the composites produced at 600 degrees C. In addition, the composites produced at 590 degrees C exhibited lower weight loss and friction coefficient.Öğe Tribological properties of hemp fiber reinforced polylactic acid bio-composites: effect of different types of modification methods(Iop Publishing Ltd, 2023) Elen, Nurhan Cevik; Yildirim, Musa; Kanbur, YasinIn this study, green composites are prepared with 30 wt.% hemp fibers reinforced polylactic acid (PLA) to enhance the impact and tribological properties. Different surface treatments of alkali and silane, compatibilizer of maleic anhydride (MA), and blends of thermoplastic polyurethane (TPU) and poly (butylene succinate) were applied to improve interfacial adhesion between fibers and matrix. Hemp-reinforced PLA bio-composites were fabricated and characterized by hardness, impact strength, wear, and friction properties. The tribological tests of the injection-molded components were performed under two different loads (10 N and 20 N) as dry-sliding linearly reciprocating motion per ASTM G133. Modified composites gave better tribological properties than unmodified composites. While no remarkable improvement was observed in the hardness value of untreated fiber-reinforced composite, alkali-treated composite reached up to 43% improvement in hardness value. In general, as the load increased, weight loss increase was observed in all composites. Unmodified bio-composite exhibited a very low weight loss and specific wear rate (SWR) compared to neat PLA under 10 N load. The SWR of the MA bio-composite had the lowest value for both loads (10 N and 20 N) compared to the other bio-samples. The TPU blended bio-composite exhibited the highest impact strength (22.96 kJ m(-2)) after pure PLA (26.5 kJ m(-2)). Therefore, due to surface treatments and blends applied to the fibers, some composites' hardness and wear resistance were increased while the impact strength and friction coefficient was decreased. Especially silane surface treatment and MA compatibilizer application increased the wear resistance of composites. When the scanning electron microscope images were examined, it was revealed that the fiber and matrix interface bonding was good, and the fibers were firmly embedded in the matrix. Furthermore, forming a protective thin film layer formed by the polymer debris from the surface during dry-sliding increased the wear performance of the bio-composites.
