Yazar "Kok, M." seçeneğine göre listele

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    THE EFFECT OF CHROMIUM ADDITION ON PHYSICAL PROPERTIES OF Cu-Al BASED HIGH TEMPERATURE SHAPE MEMORY ALLOY
    (Polska Akad Nauk, Polish Acad Sciences, Inst Metall & Mater Sci Pas, 2018) Cirak, Z. Deniz; Kok, M.; Aydogdu, Y.
    Cu-Al-based high temperature shape memory alloys are preferred commonly due to their cheap costs and shape memory properties. In recent years, studies have been conducted on developing and producing a new type of Cu-Al based shape memory alloy. In this study, the CuAl-Cr alloy system, which has never been produced before, is investigated. After production, the SEMEDX measurements were made in order to determine the phases in the Cu84-xAl12Crx+4 (x = 0, 4, 6) (weight %) alloy system; and precipitate phases together with martensite phases were detected in the alloys. The confirmations of these phases were made via x-ray measurements. The same phases were observed by XRD diffractogram of the alloys as well. The values of transformation temperature of alloys were determined with Differential Scanning Calorimetry (DSC) at 20 degrees C/min heating rate. According to the DSC results, the transformation temperature of the alloys varies between 320 degrees C and 350 degrees C. This reveals that the alloys show high temperature shape memory characteristics.
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    The effect of Sn content on mechanical, magnetization and shape memory behavior in NiMnSn alloys
    (Elsevier Science Sa, 2016) Aydogdu, Y.; Turabi, A. S.; Kok, M.; Aydogdu, A.; Yakinci, Z. D.; Aksan, M. A.; Yakinci, M. E.
    The effects of the composition alteration on the magnetization and shape memory behavior of Ni50Mn40-xSn10+x (x = 0, 1, 2, 3) alloys were systematically investigated by thermal, magnetic and mechanical experiments. Phase transformation from ferromagnetic austenite to weakly magnetic martensite was observed during thermal cycling under magnetic field and transformation temperatures were decreased with increasing Sn (or decreasing Mn). Moreover, the saturation magnetization of martensite increased with Sn content. Ni50Mn40Sn10 showed the recoverable strain of 2.1% during thermal cycling under 300 MPa and the reversible superelastic strain of 2% at 190 degrees C. Mechanical experiments exhibited that the largest compressive deformation of about 7% at 650 MPa occurred in Ni50Mn39Sn11 while Ni50Mn40Sn10 had fractured at 4% and 390 MPa at room temperature. (C) 2016 Elsevier B.V. All rights reserved.
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    The effects of boron addition on the magnetic and mechanical properties of NiMnSn shape memory alloys
    (Springer, 2016) Aydogdu, Y.; Turabi, A. S.; Aydogdu, A.; Kok, M.; Yakinci, Z. D.; Karaca, H. E.
    The effects of boron addition on the microstructure, magnetic, mechanical, and shape memory properties of Ni50Mn40-xSn10Bx (at.%) (x = 1, 2, 3, 4, 6, 8) polycrystalline alloys were systematically investigated. It was revealed that transformation temperatures, magnetic behavior, mechanical, and shape memory properties can be tailored by B content. Transformation temperatures were decreased while saturation magnetization was increased with the addition of boron. In addition to magnetic behavior, ferromagnetic austenite transforms to weakly magnetic martensite, and then, martensite becomes ferromagnetic during cooling. The low amount of B addition (up to 4 %) to NiMnSn creates the second phase which provides higher strength and ductility. However, the high volume fraction of the second phase reduces the shape recovery because the phase transformation does not occur in the second phase. Brittleness takes place when the B amount is more than 6 % in NiMnSnB alloys. The amount of boron content in the NiMnSnB alloys plays a significant role to modify the magnetic, mechanical, and shape memory properties.
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    The effects of substituting B for Cu on the magnetic and shape memory properties of CuAlMnB alloys
    (Springer Heidelberg, 2016) Aydogdu, Y.; Turabi, A. S.; Aydogdu, A.; Vance, E. D.; Kok, M.; Kirat, G.; Karaca, H. E.
    The effects of B addition on the magnetization, mechanical and shape memory properties in Cu70-xAl24-Mn6Bx at.% (x = 0, 1, 2, 3, 4) alloys have been investigated. The ductility was decreased, while the strength was improved with B addition. Transformation temperatures were increased with B content due to increased e/a ratio. Martensite start temperature of B-free CuAlMn was found to be 37.3 degrees C and increased to 218.8 degrees C with 4 % B addition. B-free CuAlMn exhibited shape memory effect with a recoverable strain of 2.25 % under 200 MPa and a perfect superelasticity with a recoverable strain of 2.5 % at 163 degrees C. B addition degraded the shape memory properties and eventually resulted in the lack of recoverable strain. In addition, saturation magnetization was increased with B content. Moreover, the addition of B slightly decreased the ductility of the alloy. It was found that the magnetization, mechanical and shape memory properties CuAlMn alloys can be tailored by quaternary alloying with B.
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    The Relationship between Cobalt Amount and Oxidation Parameters in NiTiCo Shape Memory Alloys
    (Maik Nauka/Interperiodica/Springer, 2020) Mohammed, S. S.; Kok, M.; Cirak, Z. D.; Qader, I. N.; Dagdelen, F.; Zardawi, H. S. A.
    Coating shape-memory alloys (SMAs) with a ceramic layer is an important way by which metallurgists change some physical properties and improve biocompatibilities of (SMAs) for some medical purposes. The oxidation behaviors of five NiTiCo samples with different compositions were investigated and their influence on the thermal characteristics of phase transformation temperatures was studied. The kinetic oxidation as a function of time was determined by using the results of measurements via a combined method of the thermal gravimetrical (TG) and differential thermal (DT) analysis (TG/DTA), at 1323 K for one hour. The SEM-EDX results showed that an oxidation layer covered the surface of the alloys with ceramic compounds consisting of titanium and oxygen. The phase transformation temperatures were increased with respect to non-oxidized NiTiCo alloys. Likewise, the enthalpy change during the heating process was affected by the oxidation process.
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    Thermal and magnetic properties of Ni51Mn28.5Ga19.5B magnetic-shape-memory alloy
    (Springer, 2014) Kok, M.; Yakinci, Z. D.; Aydogdu, A.; Aydogdu, Y.
    Ni51Mn28.5Ga19.5B magnetic shape-memory alloy was produced in Arc melter under vacuum. The crystal structure of the produced alloy was determined by using XRD. The XRD analysis results indicated the presence of two phases; namely the martensitic phase that the alloy was determined to display non-modulated martensitic phase and the gamma phase characteristics. DSC was used to determine the transformation temperature, the thermodynamic quantities of martensitic transformation and the activation energy in the Ni51Mn28.5Ga19.5B alloy. The austenite transformation temperature and activation energy of transition were found as 46.92 A degrees C and 303.12 kJ mol(-1) respectively. The 1 % presence of the boron element in the alloy was observed to play a significant role in the transition temperature as indicated by the comparison of the values obtained in this study with those available in the literature. The magnetic properties of this alloy were determined using the PPMS instrument. The magnetic saturation value was determined as 66 emu g(-1).