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Öğe Dry sliding wear behavior of low carbon dual phase powder metallurgy steels(Elsevier Sci Ltd, 2007) Tekeli, S.; Gural, A.; Ozyurek, D.Dry sliding wear behavior of Fe + 0.3% graphite powder metallurgy processed (PM) steels was investigated at constant sliding speed, load and distance. For this purpose, atomized iron powder was mixed with 0.3% graphite powder and sintered at 1200 degrees C for 30 min under Argon gas atmosphere. The sintered PM specimens were intercritically annealed at different temperatures (728 and 760 degrees C) and then water-quenched. After sintering, a typical ferrite + pearlite microstructure was obtained. In the microstructure of the intercritically annealed PM specimens, a ferrite + martensite microstructure was produced. After wear tests, it was seen that the wear rate of the intercritically annealed specimens was very low in comparison to as-sintered specimen. The specimen intercritically annealed at 728 degrees C showed the lowest wear rate, despite its lower martensite volume fraction. (c) 2006 Elsevier Ltd. All rights reserved.Öğe EFFECT OF Al2O3 AMOUNT ON MICROSTRUCTURE AND WEAR PROPERTIES OF Al-Al2O3 METAL MATRIX COMPOSITES PREPARED USING MECHANICAL ALLOYING METHOD(Springer, 2010) Ozyurek, D.; Tekeli, S.; Gural, A.; Meyveci, A.; Guru, M.This paper reports the outcome of an investigation into the effect of Al2O3 content on the microstructure and wear properties of Al-Al2O3 metal matrix composites. The Al-Al2O3 composites are prepared by a mechanical alloying method using Al2O3 powders up to 20 vol.% as reinforcement. Alloying is performed in a vibration mill using a ball-to-powder ratio 10: 1 and a milling time varying from 30 to 100 min at a rate of 710 Hz. The prepared compositions are cold pressed at 630 MPa with a single action and sintered at 560 degrees C for 30 min under Ar gas atmosphere. The experimental results show that the reinforcing phase Al2O3 is homogeneously dispersed in the Al matrix and the interface between Al matrix and Al2O3 is well formed. Wear tests are carried out under dry sliding conditions using a pin-on-disk testing machine at three different loads of 10, 25, and 50 N and at a sliding speed of 2.08 m/sec. Total sliding distances are selected as 400, 800, 1200, and 1600 m. It is seen that the wear rate decreases with increasing Al2O3 content and sliding distance at a sliding speed of 2.08 m/sec.Öğe The effect of diffuser and non-diffuser runner systems on the mechanical properties of A356 alloy(2013) Tunçay, T.; Tekeli, S.; Özyürek, D.In this study, runner systems which have equal cross-sectional area and different forms of cross-sectional diffuser and non-diffuser runner system's effects on mechanical properties of A356 aluminium alloy, depending on the movement of the liquid metal, were investigated. The aim of the study is to reduce casting defects due to inclusion caused by runner systems such as gas or shrinkage porosity. Therefore, the horizontal runners have been extended by using diffusers having cross-sectional area equivalent with a different cross-sectional shape (square, rectangular and circular outlet). Tensile test specimens were prepared from the plates of casting A356 alloy and tensile tests were performed. Obtained results were examined Weibull statistical analysis. As a result, one hand, it is observed that the turbulence effect on liquid metal has been decreased the highest tensile results and Weibull modulus has been appeared on the samples which have horizontal runners produced by using a square section diffuser in designed horizontal diffuser. On the other hand, according to Scanning Electron Microscope (SEM) analysis on fracture surfaces, fracture has been observed in the area of intermetallic secondary phases (oxides etc.) and in area with gas or shrinkage porosity.Öğe Effect of repeated quenching heat treatment on microstructure and dry sliding wear behavior of low carbon PM steel(Trans Tech Publications Ltd, 2007) Güral, A.; Tekeli, S.; Özyürek, D.; Gürü, M.The effect of repeated quenching heat treatment on microstructure and dry sliding wear behavior of low carbon PM steel was investigated. For this purpose, atomized iron powder was mixed with 0.3 % graphite and 1 % Ni powders. The mixed powders were cold pressed and sintered at 1200°C for 30 min under pure Ar gas atmosphere. Some of the sintered specimens were intercritically annealed at 760°C and quenched in water (single quenching). The other sintered specimens were first fully austenized at 890°C and water quenched. These specimens were then intercritically annealed at 760°C and re-quenched in water. The martensite volume fraction in the double quenched specimens was higher than that of the single quenched specimen. Wear tests were carried out on the single and double quenched specimens under dry sliding wear condition using a pin-on-disk type machine at constant load and speed. The experimental results showed that the wear coefficient effectively decreased in the double quenched specimen.Öğe The effect of the aging time on microstructure and mechanical properties of the AA7075 alloy after T6 heat treatment(G.V. Kurdyumov Institute for Metal Physics of N.A.S. of Ukraine, 2019) Simsek, I.; Simsek, D.; Ozyurek, D.; Tekeli, S.In this study, the effect of the aging time on microstructure and mechanical properties of the AA7075 alloy after T6 heat treatment is investigated. The AA7075 alloys are quenched after solid solution treatment at 485°C for 2 hours and artificially aged at 120°C using five different aging times. Hardness measurements, microstructure examinations (SEM + EDS, XRD), and tensile tests are performed for the aged alloys. Fractured surfaces are also examined using SEM images after the tensile testing. The results of the studies conducted show that the hardness value of the alloys can be increased by increasing aging time, and the maximum hardness value of 192 HV is obtained for the alloy aged for 25 hours. Tensile tests also show that the tensile strength of the alloy can be increased by increasing aging time, and the maximum tensile strength value of 580 MPa is obtained for the alloy aged for 25 hours. Fractured surface examinations revealed that the ductile fracture mechanism is mostly dominant, while the planar fracture mechanism is observed as well. © 2019 G. V. Kurdyumov Institute for Metal Physics, National Academy of Sciences of Ukraine.Öğe Exchange of experience the effect of synthesis time on the wear behavior of Al-8%Ti alloy produced by mechanical alloying(Springer, 2012) Ozyurek, D.; Tekeli, S.; Tuncay, T.; Yilmaz, R.In this study, Al-8%Ti alloy was produced by mechanical alloying. The produced powders were cold pressed at 630 MPa and synthesized at 600A degrees C for 12 and 24 h under argon gas atmosphere. After synthesis processes, the specimens were examined by SEM, XRD, and hardness tests. Wear tests were carried out under dry sliding conditions using a pin-on-disk type machine at a constant load of 30 N and a sliding speed of 1 m/sec. Total sliding distances were selected as 500, 1000, 1500, and 2000 m. The experimental results showed that the hardness and density of Al-%8Ti alloy increased with increasing synthesis time. It was also observed that volume reduction increased with increasing sliding distance and decreased with increasing synthesis time.Öğe An investigation on wear resistance of SiCp-reinforced aluminium composites produced by mechanical alloying method(2010) Özyürek, D.; Tekeli, S.In this study, Al-SiCp composites were produced by a mechanical alloying method using SiCp powders up to 20 voI% as a reinforcement. The produced compositions were cold pressed at 630 MPa with a single action and sintered at 560°C for minutes under Ar gas atmosphere. The experimental result showed that the reinforcement phase SiCp was homogeneously dispersed in the A1 matrix and the interface between A1 matrix and SiC p was well formed. Wear tests were carried out under dry sliding conditions using a pin-on-disk type testing machine at three different loads of ION, 25N and 50N and at a sliding speed of 2.08 m/s. Total sliding distance was selected as 400, 800, 1200 and 1600 m. After wear tests, the wear amount was determined by measuring the weight and dimension of specimens. It was seen that the wear rate increased with increasing the applied load from 10N to 50N, sliding distance and decreased with increasing SiCp amount. Microstructures and worn surface of Al-SiCp composites were investigated by SEM.Öğe Microstructure and dry sliding wear properties of 3Si-2Ni and 3Si-2Mn powder metallurgy steels with different graphite content(Sage Publications Ltd, 2011) Tekeli, S.; Gural, A.; Ozyurek, D.In this study, plain iron powder (ASC.100.29) was mixed with 0.35-1.1 % graphite + 3 % Si + 2 % Ni and 0.35-1.1 % graphite + 3 % Si + 2 % Mn powders. While coarse pearlitic structure with homogeneous distribution of Mn was obtained in Mn-added specimens, Ni-rich austenitic areas with divorced pearlite structure were observed in Ni-added specimens. Wear tests were carried out at a load of 50 N. The experimental results showed that the highest wear resistance was obtained in the Ni-added specimen. While subsurface brittle cracking caused more wear in the Mn-added specimens, the wear occured by plastic deformation of surface Ni-added specimens.
