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    Effect of Zr Concentration on the Microstructure and Mechanical Performance of Porous Ti-Zr System by Powder Metallurgy
    (Trans Tech Publications Ltd, 2022) Karakurt, E.M.; Huang, Y.; Kaya, M.; Demirtas, H.; Cakmak, O.
    In this study, porous binary Ti-(x)Zr alloys of nominal Zr contents (x=10, 20 and 30 at. %) with differing porosities were manufactured, using powder metallurgy with compaction conducted under a pressure of 300MPa and sintering at 1200 ?C for 6 h. A space holder agent was employed to control the general porosity. The microstructures were characterized by scanning electron microscopy and energy dispersed spectroscopy. The phase constitution was done by X-ray diffractometer. Uniaxial compressive tests were performed to determine the mechanical behaviours. Microstructural studies revealed macro/micro pores generated were mostly irregularly shaped with a uniform pore size distribution in all Ti-(x)Zr (at. %) alloys. The finer microstructure was obtained with increasing Zr contents. The mechanical performances of the porous Ti-(x)Zr (at. %) binary systems were strongly influenced by Zr and general porosity. © 2022 Trans Tech Publications Ltd, Switzerland.
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    Evaluation of dry sliding wear behavior of NiAl base materials
    (TUBITAK, 2020) Demirtas, H.
    In this study, the wear behaviour of NiAl intermetallic, NiAl/Cr-Mo pseudo-eutectic and NiAl-Ti/Cr-Mo alloys which is considered as alternative material in different applications were investigated. Wear tests were performed against steel (AISI 52100) and ceramic (Al2O3) balls. Test specimens were produced by arc melting method and abrasion tests were performed by ball on flat method under dry sliding conditions. Wear results were examined by hardness measurements, SEM investigations and EDX analyzes. As a result of the studies, it was found that the amount of abrasion loss determined in the experiments using steel balls was much higher than that of ceramic balls. Among the materials, the highest losses were seen in NiAl intermetallic in both abrasive balls, while the lowest losses were determined in Ti added pseudo-eutectic NiAl/Cr-Mo alloy. © 2020, TUBITAK. All rights reserved.
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    Improvement of mechanical properties of NiAl-Cr(Mo) alloy by Ti addition
    (Natl Inst Optoelectronics, 2015) Demirtas, H.; Gungor, A.
    In this study, the influence of 4, 5 and 6 at.% Ti addition on the mechanical properties of NiAl-Cr(Mo) eutectic alloy was investigated. The microstructure of the alloys were determined by using XRD, SEM, EDX analyses and mechanical properties were investigated by micro and macro hardness measurements and compression tests at room temperature and 1000 degrees C. The results showed that Ni2AlTi Heusler phase precipitated in all Ti-added alloys and Ti addition inhibited eutectic cell formation by transforming lamellas Cr(Mo) phase into Cr(Mo) dendrites. In addition, hardness, room temperature and high temperature mechanical properties of NiAl-Cr(Mo) alloy improved significantly with the Ti addition.
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    Improvement of mechanical properties of NiAl-Cr(Mo) alloy by Ti addition
    (National Institute of Optoelectronics, 2015) Demirtas, H.; Gungor, A.
    In this study, the influence of 4, 5 and 6 at.% Ti addition on the mechanical properties of NiAl-Cr(Mo) eutectic alloy was investigated. The microstructure of the alloys were determined by using XRD, SEM, EDX analyses and mechanical properties were investigated by micro and macro hardness measurements and compression tests at room temperature and 1000 °C. The results showed that Ni2 AlTi Heusler phase precipitated in all Ti-added alloys and Ti addition inhibited eutectic cell formation by transforming lamellas Cr(Mo) phase into Cr(Mo) dendrites. In addition, hardness, room temperature and high temperature mechanical properties of NiAl-Cr(Mo) alloy improved significantly with the Ti addition. © 2015, National Institute of Optoelectronics. All rights reserved.
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    Influence of Nano-WC Addition on Wear Performances of Cu-Ni Matrix Nanocomposites
    (Polish Acad Sciences Inst Physics, 2019) Cug, H.; Demirtas, H.; Erden, M. A.; Akgul, Y.; Turan, M. E.; Zengin, O.
    The present study focuses on the effect of tungsten carbide content on wear behavior of Cu based composites which are generally preferred in engineering applications. Nickel 4 wt% was used as the binding agent in order to develop wetting ability between matrix and reinforcement. Cu-4Ni matrix composites were fabricated via powder metallurgy incorporating the different amount of present study focuses on the effect of tungsten carbide (0.5, 1 and 2 wt%). Wear tests were conducted using three different loads (5 N, 10 N and 20 N) in dry sliding conditions. Results showed that hardness of the composites increased with increasing tungsten carbide content. Tungsten carbide additions also lead to improving the wear resistance of copper matrix composites. Abrasive wear mechanism was generally observed for all samples especially for higher loads according to the scanning electron microscope (SEM) results
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    Microstructure and mechanical properties of Fe-doped NiAl-28Cr-6Mo eutectic alloys
    (Elsevier Science Bv, 2016) Gungor, A.; Demirtas, H.
    Room temperature and high temperature microstructural and mechanical properties of arc melted NiAl-28Cr-6Mo eutectic alloys doped with 0.1% Fe, 0.2% Fe and 0.5% Fe (mole fraction) were investigated. The homogenization heat treatment of the alloys was conducted at 1300 degrees C in Ar atmosphere. Microscopic analyses, hardness measurements, XRD measurements and compression tests were used to characterize the alloys. As-cast and homogenized alloys exhibit fine cellular eutectic structures with coarse intercellular eutectic structure. The increase in the content of Fe results in coarsening eutectic layers and the decrease in eutectic cells. All alloys have very high compressive stress and strain at room temperature. The addition of Fe has small negative impact on the strength and ductility of the alloys at room temperature. However, the addition of Fe increases the high temperature strength of the alloy. High temperature XRD patterns show that peaks shift to lower Bragg angles. This indicates that the lattice parameter of the alloys increases.