Browsing by Author "Kiliçaslan M."

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Formation of novel rice-like intermetallic phases and changes in the mechanical, microstructural and electrical properties of Sn-5Sb alloys with addition Ag and Bi
(2016-01-15) Karaköse E.; Kiliçaslan M.; Çolak H.
In the present study, the effects of Ag and Bi additions (1 wt.%) on the microstructural, thermal, mechanical and electrical properties of Sn-5Sb solder alloys were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), microhardness tests, and four probe measurements. It was observed that the melting point of Sn-5Sb solder alloy decreased with the addition of Ag and Bi. It was found that the final microstructure of rapidly solidified Sn-5Sb-1X (X = Ag and Bi) alloys was strictly dependent upon the wheel speeds; the microstructures changed from a coarse dendritic and needle-like structure to a refined ultra fine dendritic and rice-like structure with increasing wheel speed. Cooling rate was also effective on both the mechanical and electrical properties. It was found that all of the alloys exhibit higher mechanical properties with increasing cooling rate and/or decreasing testing temperature. Similarly, significant improvements of 32% and 9% in electrical conductivity of both of the alloys were obtained with the addition of Ag and Bi, respectively. The microstructural evolution of the Sn-5Sb based alloys plays a crucial role in influencing the mechanical properties of these alloys.
Microstructure and microhardness of melt-spun Al-25Si-5Fe-XCo (X = 0, 1, 3, 5) alloys
(2013-02-01) Kiliçaslan M.; Yilmaz F.; Ergen S.; Hong S.; Uzun O.
The microstructure and microhardness evolution of melt-spun Al-25Si-5Fe alloy with Co addition (1, 3 and 5 wt.%) were investigated. Microstructural and spectroscopic analyses demonstrate that Co could refine primary Si grains and change their morphology because it causes higher constitutional undercooling and has large mixing enthalpy with Si. Especially, 3 wt.% Co addition causes homogeneously distributed fine spherical Si particles in the rapidly solidified Al-25Si-5Fe alloy. The size of the spherical silicon particles was from around 200 to 600 nm near the wheel side region, and it varied from 800 nm to 1.3 μm at the air side. The optimum ratio of Si and Co should be between 6 and 8.3 to form spherical Si grains in Al-25/30Si-5Fe alloys. A considerable improvement in microhardness value (from 211 to 370 HV) was obtained with the addition of Co. © 2013 Elsevier Inc.
Shape memory properties and microstructural evolution of rapidly solidified CuAlBe alloys
(2013-05-03) Ergen S.; Uzun O.; Yilmaz F.; Kiliçaslan M.
In this work, the effects of Be addition on the microstructure and phase transformation temperatures of Cu-12Al-xBe (x = 0.4, 0.5 and 0.6 wt.%) shape memory alloys fabricated by using the arc-melting and melt-spinning techniques have been investigated. X-ray diffraction analysis revealed that the arc-melted alloys consisted of austenitic β1, martensitic β1′ and γ2 precipitate phases, whereas melt-spun ribbons were composed of a fully martensitic phase. The average grain size of martensitic phases in melt-spun ribbons was determined by electron microscopy images, showing a decrease with increasing Beryllium (Be) amount. Moreover, it was found that the Be addition in the arc-melted alloys had a distinct effect on the morphology of the γ2 precipitate phase. Transmission electron microscopy analysis showed that the thickness of martensitic plates in the melt-spun ribbons reduced with increasing Be addition. In a differential scanning calorimeter analysis, no martensitic transformation (Ms) peak was observed in arc-melted alloys, but it was clearly detected in melt-spun ribbons, in which Ms decreased dramatically with increasing Be addition. The improvement in the shape memory ability of melt-spun ribbons was explained in terms of the refinement in grain size and martensitic plates. © 2013 Elsevier Inc.