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1
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In Situ Formation of Ti-TiAl₃ Metallic-Intermetallic Composite by Electric Current Activated Sintering Method

100%
Yener T., Okumus S., Zeytin S.
Acta Physica Polonica A
|
2015
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vol. 127
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issue 4
917-920
EN
In this study we have investigated fabrication of in situ metallic- intermetallic Ti-TiAl₃ composites from powder mixture containing 40 wt % Ti-Al, 50 wt % Ti-Al and 60 wt % Ti-Al by electric current activated sintering method. Powder mixtures without additive were compressed uniaxially under 130 MPa of pressure and sintered 2000 A current for 20 minutes in a steel mould. Microstructures of sintered samples were investigated by optic and scanning electron microscopes, phases in samples were analyzed by XRD and their hardness was measured by Vickers hardness tester. Optic and scanning electron microscopes investigations showed that microstructures of samples were consisting of two components: Main component was titanium aluminide and other was metallic titanium. Besides this there was a trace amount of aluminium oxide in the sintered body. XRD analyses also demonstrated that main phase is TiAl₃. It was determined that as weight percentage of titanium in the mixture was decreasing, also the amount of metallic titanium has decreased in the sintered body. Additionally, average hardness values of samples were about 500 HV
2
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Pack Siliconizing of Ti6Al4V Alloy

100%
Celebi Efe G., İpek M., Bindal C., Zeytin S.
Acta Physica Polonica A
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2017
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vol. 132
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issue 3
760-762
EN
In this study, it was aimed to produce titanium silicide layer on Ti6Al4V by a simple, cheap and efficient method of pack siliconizing. Siliconizing was performed in a pack containing a mixture composed of SiO₂ powder as siliconizing source, pure Al powder as a reducer for siliconizing, NH₄Cl as an activator and Al₂O₃ powder as filler, at 1000°C for 8, 10 and 12 hours in open atmospheric furnace. Optical microscope and SEM-EDS studies indicate that the morphology of silicide layers has smooth, dense and layered nature. The presence of phases, confirmed by XRD analyses, reveals that the silicide layers formed at 1000°C are composed of TiSi₂, Ti₃Si₅, TiN, TiO₂ and SiO₂ compounds. Silicide layer thickness was increased with increasing process time and ranged from 7.5 to 9.0 μm. Hardness of silicide layers, measured by Vickers indentation, is over 2100 HV.
3
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Effects of SiC Particle Size on Properties of Cu-SiC Metal Matrix Composites

88%
Celebi Efe G., Altinsoy I., Ipek M., Zeytin S., Bindal C.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1
251-253
EN
This paper was focused on the effects of particle size and distribution on some properties of the SiC particle reinforced Cu composites. Copper powder produced by cementation method was reinforced with SiC particles having 1 and 30 μm particle size and sintered at 700°C. Scanning electron microscopy studies showed that SiC particles were dispersed in copper matrix homogeneously. The presence of Cu and SiC components in composites were verified by X-ray diffraction analysis technique. The relative densities of Cu-SiC composites determined by Archimedes' principle are ranged from 96.2% to 90.9% for SiC with 1 μm particle size, 97.0% to 95.0% for SiC with 30 μm particle size. Measured hardness of sintered compacts varied from 130 to 155 HVN for SiC having 1 μm particle size, 188 to 229 HVN for SiC having 30 μm particle size. Maximum electrical conductivity of test materials was obtained as 80.0% IACS (international annealed copper standard) for SiC with 1 μm particle size and 83.0% IACS for SiC with 30 μm particle size.
4
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Determination of the Young Modulus of Ti-TiAl₃ Metallic Intermetallic Laminate Composites by Nano-Indentation

88%
Yener T., Güler S., Siddique S., Walther F., Zeytin S.
Acta Physica Polonica A
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2016
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vol. 129
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issue 4
604-606
EN
Nano-indentation is an important technique to determine the Young modulus of multiphase materials where normal tensile tests are not appropriate. In this work, Ti-TiAl₃ metallic-intermetallic laminate composites have been fabricated successfully in open atmosphere using commercial purity Al and Ti foils with 250 μm and 500 μm initial thicknesses, respectively. Sintering process was performed at 700°C under 2 MPa pressure for 7.5 h. Mechanical properties including the Young modulus were determined after manufacturing. The Young moduli of metallic and intermetallic phases were determined as 89 GPa and 140 GPa, respectively. Microstructure analyses showed that aluminum foil was almost consumed by forming a titanium aluminide intermetallic compound. Titanium aluminides grow up through spherical shaped islands and metallic-intermetallic interface is a wavy form in Ti-Al system. Thus, the final microstructure consists of alternating layers of intermetallic compound and unreacted Ti metal. Microstructure and phase characterizations were performed by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Hardness of test samples was determined as 600 HV for intermetallic zone and 130 HV for metallic zone by the Vickers indentation method.
5
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Comparing of Commercial and Cemented Cu-SiC Composites

76%
Celebi Efe G., Altinsoy I., Yener T., Ipek M., Zeytin S., Bindal C.
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vol. 125
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issue 2
417-419
EN
SiC with 30 μm particle size reinforced copper composites have been fabricated by powder metallurgy method and sintered at 700C for 2 h in open atmosphere. Copper powder was produced by cementation method and obtained as commercial for comparing. Cemented and commercial copper powders were reinforced with SiC having 30 μm particle size at ratios of 0, 1, 2, 3, and 5 wt% for improving mechanical properties of copper without decreasing the electrical conductivity. The presence of Cu and SiC which are dominant components in the sintered composites were confirmed by X-ray diffraction analyses technique. Scanning electron microscope showed that SiC particles are distributed homogeneously in the copper matrix. The relative densities of Cu and Cu-SiC composites sintered at 700C are ranged from 98.0% to 96.2% for commercial Cu-SiC composites, 97.55 to 95.0% for cemented Cu-SiC composites, microhardness of composites ranged from 133 to 277 HV for commercial Cu-SiC composites and 127 to 229 HV for cemented Cu-SiC composites, and the electrical conductivity of composites changed between 95.6%IACS and 77.2%IACS for commercial Cu-SiC composites, 91.7%IACS and 69%IACS for cemented Cu-SiC composites. It was observed that there is a good agreement between cemented Cu-SiC and commercial Cu-SiC composites.
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