Yazar "Muhaffel, Faiz" seçeneğine göre listele

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    Indentation creep behavior of Fe-8Ni-xZr oxide dispersion strengthened alloys
    (Walter De Gruyter Gmbh, 2023) Tekin, Mustafa; Muhaffel, Faiz; Kotan, Hasan; Baydogan, Murat
    This study was conducted to understand the creep behavior of two oxide dispersion strengthened alloys containing Zr as the alloying addition by performing indentation creep tests at room temperature. The oxide dispersion strengthened alloys were Fe-8Ni-xZr (x = 1 and 4 at.%, i.e., Zr-1 and Zr-4 alloys, respectively), which had been previously fabricated by mechanical alloying; followed by consolidation via equal channel angular extrusion at 1000?. The indentation tests were conducted under a maximum load of 100 mN with the loading rates at 300 and 400 mN min(-1). The hardness was calculated by the Oliver-Pharr method, and the creep properties, such as the creep displacement, creep strain rate, creep stress, and stress exponent n, were determined. The results showed that the Zr-4 alloy was harder than the Zr-1 alloy. However, the creep resistance of the Zr-1 alloy was better than that of the Zr-4 alloy. It was further demonstrated that both the hardness and creep resistance depended on the loading rate. Moreover, a possible creep mechanism was proposed. Although the tests were performed at room temperature, they can provide insight into the effect of an oxide dispersion strengthened alloys microstructure on creep at higher temperatures.
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    Influence of Electrolyte Compositions and Electrical Parameters on Thermal Properties of Micro-Arc Oxidized AZ91 Alloy
    (Springer, 2021) Selvi, Ekin; Muhaffel, Faiz; Yürektürk, Yakup; Vanli, Ali Serdar; Baydogan, Murat
    In this study, AZ91 Mg alloy was micro-arc oxidized using different voltages in silicate- and aluminate/phosphate-based (dual) electrolytes that included K2ZrF6 or Na2ZrO3 as the Zr source for synthesizing ZrO2 in the micro-arc oxidation (MAO) coatings. Structural characterizations were done by using scanning electron microscopy and x-ray diffraction techniques. MAO coating characteristics of different samples were compared by measuring coating thickness, surface roughness, average pore size, and total pore fraction. Both hardness and pull-off tests were conducted to characterize the mechanical properties of the coatings. Thermal conductivity measurements and thermal shock tests were also carried out to evaluate the effect of the electrolyte composition and the type of Zr containing compound. It was found that the equivalent thermal conductivity of the MAOed samples can be reduced up to 30% compared to the bare AZ91 alloy. The decrease of the thermal conductivity was mainly attributed to formation of a thicker and denser MAO coating, and the incorporation of ZrO2 phase into the fabricated MAO coating. Finally, increased thermal shock resistance was strongly correlated with a lower hardness and higher cohesive strength of the MAO coating, which also leads to smaller crack formation and spallation-free surface characteristics.
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    Surface characteristics of plasma electrolytic oxidation coatings on Cp-Ti and hot-dip aluminised Cp-Ti
    (Taylor & Francis Ltd, 2022) Celtik, Cansu; Yurekturk, Yakup; Gecu, Ridvan; Kaboglu, Cihan; Muhaffel, Faiz
    Plasma electrolytic oxidation (PEO) coatings on commercial pure titanium (Cp-Ti) and hot-dip aluminised Cp-Ti surfaces were prepared in an alkaline electrolyte. The morphological, structural, wear, and corrosion characteristics of the coatings were studied by using SEM, EDS, XRD, electrochemical polarisation, and dry sliding wear tests. The experimental results showed that the main compositions of the PEO coating on Cp-Ti are TiO2 and Al2TiO5 phases, while the PEO coating on hot-dip aluminised (HDA'ed) Cp-Ti mainly consists of the Al2O3 phase. The single PEO coating exhibited more porosity with small diameter micro-pores compared to the PEO coating on the HDA'ed sample. Electrochemical polarisation tests revealed that the PEO coating on the HDA'ed sample exhibited approximately 4.6 times more polarisation resistance than the single PEO coating and 10 times that of the bare Cp-Ti sample. According to the wear test results, the wear resistance of the bare Cp-Ti was doubled by hot-dip aluminising (HDA) and PEO treatments, while the single PEO treatment resulted in better resistance against dry sliding wear.