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RISS 인기검색어
- 검색키워드
- 저자 : F. Dagdelen (검색결과 3 건)
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F. Dagdelen,M. Kok,I. N. Qader 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.6
In the present work, Ni32-x-Ti-Ta18+x (x = 0, 2, 3, 4, 5, 6, 7, 8) shape memory alloys, produced by arc-melting method. Then,differential scanning calorimetry (DSC), optical microscopy (OM), x-ray diffraction (XRD), and Vickers micro-hardnessmeasurements were carried out to investigate thermodynamic parameters, microstructure, crystal structure, and mechanicalproperties of the alloys, respectively. The DSC results showed that, as the amount of Ta increased, the phase transformationtemperatures of the specimens significantly changed. In addition, increasing of Ta composition raised the mass density andelectron participation of NiTi alloy, and thus, the vibrational term of entropy overcomes the electron participation; consequently,the total entropy declined in the alloys. It is found that OM images possess a dendritic microstructure, where byincreasing the amount of Ta, the dendrites length increase while random orientations decrease. Moreover, XRD patternsexhibited the existence of each austenite phase (B2), martensite phase (B19ʹ), and β-Ta riched phase in all samples.
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S. Buytoz,F. Dagdelen,I. N. Qader,M. Kok,B. Tanyildizi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5
Improving shape memory alloys in term of microstructural analysis is important for some related applications. In this study,three diff erent NiTiHf shape memory alloys were produced from high pure elements and by utilizing arc-melting device.The morphologies of diff erent precipitations and microstructures were analyzed by optical microscope, mapping, and EDXcompositional analysis. The DSC measurements showed that the phase transformation temperatures is increased by addingmore hafnium instead of nickel content in NiTiHf alloy, however, the enthalpy change for both endo/exothermic processwere decreased. Also, XRD analysis has been carried out for all alloys to fi nd diff erent phases, and to obtain grain size as afunction of diff erent composition of Ni and Hf elements. The oxidation shows that titanium dioxide (TiO 2 ) is spread out overthe surface, but the microstructures are completely diff erent for each case, e.g. needle-like shapes (nanorods) has extendedover the surface of Alloy A with 3 at% Hf, but plate-like Ti-rich microstructures is dominated on the surface of Alloy B thathas twice as more Hf as Alloy A; on the other hand, Alloy C with 9 at% Hf has some precipitates with TiO phase.
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C. Ozay,H. Ballikaya,F. Dagdelen,O. E. Karlidag 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.7
In this study, the surface of an AA-2024 alloy was covered with reinforced composite coating using hotpress sintering method. Al and B 4 C powders were synthesized through mechanical alloying technique and coated on the AA-2024 substrate at different rates. The microstructure of the intermediate transition region formed between the substrate (AA-2024 Al alloy) and the coating layer (Al/B 4 C MMCs), the microstructure of the Al/B 4 C metal matrix composites (MMCs) coating, the microhardness, and the adhesive wear resistance of the Al/B 4 C MMCs coating layer were investigated. It was observed that B 4 C powders homogeneously dispersed in the microstructure of the Al/B 4 C MMCs coating layer, moreover, the Al matrix and B 4 C reinforcement particles were bonded without a gap. It was also determined that an interface bonding occurred between Al/B 4 C MMCs coating layer and the AA-2024 substrate. Accordingly, it was determined that with the increase of B 4 C reinforcement particle ratio, the hardness of the coating layer, and the wear resistance increased.
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