Browsing by Author "Kilicaslan M."

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Densification behaviour analysis of ZrO2 nanopowders for dental applications compacted by magnetic pulsed compaction
(2013-08-15) Park H.; Kilicaslan M.; Hong S.
Sintered bulks of commercial ZrO2 nanopowders were produced by combined application of magnetic pulsed compaction (MPC) and subsequent two-step sintering, and finally, their density, hardness, shrinkage and formability were analyzed. The formability tests were conducted by a CAD/CAM system. Nearly fully dense (∼98%) commercial ZrO2 bulks were successfully obtained. With increasing MPC pressure, there was a decrease in the grain size of zirconia block. The ratio of PVA did not have a remarkable effect on the grain size. The optimum compaction pressure during MPC was 1 GPa and mixing conditions included using 1.0 wt. % PVA. The optimum processing condition included MPC process, followed by two-step sintering (first at 1000 and then at 1450 C). The bulk under these conditions was found to have good formability, ∼97% density, reasonable hardness (1150 Hv) and ∼19% shrinkage© 2013 Elsevier B.V. All rights reserved.
Effect of multiple pressures by magnetic pulsed compaction (MPC) on the density of gas-atomized Al-20Si powder
(2012-07-01) Park H.; Kilicaslan M.; Hong S.
Rapidly solidified Al-20. wt.%Si alloy powders with particle size of ~. 106. μm in diameter were fabricated by gas atomization, and the powder compaction was performed by using magnetic pulsed compaction. Multiple way experiments were carried out on Al-Si powders with varying pressing time, weight and intensity of initial and final pressures. Effects of process parameters during multiple pressing such as, number of repeated pressing, initial pressure, and final pressure, on the density were investigated. It was found that density decreases with increasing weight of powder poured to the die, but it enhances with increasing pressure. The last compaction pressure has a more dominant effect on the density than the initial compaction pressure in magnetic pulsed compaction process. With increasing the number of repeated pressing, the density of the compacted product increases. © 2012 Elsevier B.V..
Effect of Sc addition on the microstructure and mechanical properties of as-atomized and extruded Al-20Si alloys
(2012-03-15) Kilicaslan M.; Lee W.; Lee T.; Sohn Y.; Hong S.
The microstructure evolution and mechanical properties of Al-20Si alloy with Sc addition were investigated after as-atomized and hot-extruded conditions. Microstructural and spectroscopic analyses demonstrate that Sc is enriched at the Si/Al interface. It could be observed that the presence of Sc refined the size of the primary and eutectic Si, without significantly affecting the shape. A considerable improvement in tensile strength, compressive strength, and elongation was observed due to addition in Sc percentage into the composition. The correlation between the microstructure and mechanical behavior strongly indicates that the addition of Sc modifies the Si particles by impurity induced twinning (IIT) mechanisms. © 2011 Elsevier B.V. All rights reserved.
Effect of v addition on the nano-size spherical particles growing on the Fe-bearing intermetallics and silicon phases of gas atomized hypereutectic Al-20Si-5Fe alloys
(2014-09-05) Kilicaslan M.
In this study, rapidly solidified hypereutectic Al-20Si-5Fe-XV (X = 0, 0.5, 1 and 1.5) alloys were fabricated by gas atomization in Ar atmosphere. Microstructural and spectroscopic analyses were performed using SEM, SEM - EDS and XRD measurements. Experimental results showed that addition of V to gas-atomized Al-20Si-5Fe alloys led to formation of a refined microstructure composed of finer Si and Fe-bearing intermetallics. Possible refining mechanism of Si phases is the IIT because of Rv:RSi is 1.38 close to the value of 1.65 which is the ideal ratio of radius for the impurity-atom to Si-atom (Ri:RSi). The reason of formation finer of δ-Al4FeSi2 phase with addition of V is that vanadium addition leads to an increment in the thermodynamic stability and a reduction in the free energy of δ-Al4FeSi2 phase. Therefore, finer and modified morphology became more favorable for δ-Al 4FeSi2 phase in terms of thermodynamic. Nanosize Si particles growing on the surface of Fe-bearing intermetallics and micro size polygonal Si phases were observed. There was no effect of V on the number of fine silicon particles growing up on the micro size polygonal Si phases. However, during solidification, addition of V led to an increase in the number of fine silicon particles growing on the Fe-bearing intermetallics. Microhardness measurements showed that there was an increase in the microhardness values of Al-20Si-5Fe alloys with addition of V, in general. ©2014 Elsevier B.V. All rights reserved.
Effect of v addition on the nano-size spherical particles growing on the Fe-bearing intermetallics and silicon phases of gas atomized hypereutectic Al-20Si-5Fe alloys
(2014-09-05) Kilicaslan M.; Kilicaslan, MF
In this study, rapidly solidified hypereutectic Al-20Si-5Fe-XV (X = 0, 0.5, 1 and 1.5) alloys were fabricated by gas atomization in Ar atmosphere. Microstructural and spectroscopic analyses were performed using SEM, SEM - EDS and XRD measurements. Experimental results showed that addition of V to gas-atomized Al-20Si-5Fe alloys led to formation of a refined microstructure composed of finer Si and Fe-bearing intermetallics. Possible refining mechanism of Si phases is the IIT because of Rv:RSi is 1.38 close to the value of 1.65 which is the ideal ratio of radius for the impurity-atom to Si-atom (Ri:RSi). The reason of formation finer of δ-Al4FeSi2 phase with addition of V is that vanadium addition leads to an increment in the thermodynamic stability and a reduction in the free energy of δ-Al4FeSi2 phase. Therefore, finer and modified morphology became more favorable for δ-Al 4FeSi2 phase in terms of thermodynamic. Nanosize Si particles growing on the surface of Fe-bearing intermetallics and micro size polygonal Si phases were observed. There was no effect of V on the number of fine silicon particles growing up on the micro size polygonal Si phases. However, during solidification, addition of V led to an increase in the number of fine silicon particles growing on the Fe-bearing intermetallics. Microhardness measurements showed that there was an increase in the microhardness values of Al-20Si-5Fe alloys with addition of V, in general. ©2014 Elsevier B.V. All rights reserved.
Effects of Substitution of Al and Bi for Ni on Structure and Hydrogen Storage Properties of LaNi 4.7-xAl 0.3Bi x (x = 0:1; 0:2; 0:3) Alloy
(2012-09-01) Yilmaz F.; Kilicaslan M.; Atanur O.; Hong S.; Uzun O.
In this research, the effects of Al and Bi substitution for Ni on the microstructure and hydrogen absorption/desorption properties of LaNi 4.7-xAl 0.3Bi x (x = 0:1; 0:2; 0:3) alloys were investigated. The results showed that substituting Ni with Al led to a desirable decrease in absorption/desorption plateau pressure as well as to hysteresis without a reduction in hydrogen capacity. However, Bi substitution reduced the hydrogen capacity and increased the absorption/desorption plateau pressure of the samples. The formation of the (Al,Ni) intermetallic and Bi phases at grain boundaries was found to be the main reason for the changes in hydrogen storage properties. © 2012 The Japan Society of Applied Physics.
Formation of novel flower-like silicon phases and evaluation of mechanical properties of hypereutectic melt-spun Al-20Si-5Fe alloys with addition of V
(2014-06-23) Uzun O.; Kilicaslan M.; Yilmaz F.
In this work, rapidly solidified hypereutectic Al-20Si-5Fe-. XV (X=0, 0.5 and 1) alloys were fabricated by melt spinning under vacuum. Microstructural and spectroscopic analyses were performed using SEM, TEM, TEM-MAPing, TEM-EDS and XRD measurements. Mechanical properties of the alloys were determined using DSI measurements. Experimental results indicated that addition of 0.5. wt% V to melt-spun Al-20Si-5Fe alloys induced formation of a novel flower-like Si phase. And addition of higher amount V (1. wt%), caused formation of refined Si phases and mostly hindered formation of Fe-bearing intermetallics. Observations along with manuscript strongly indicate that V modifies the Si phases by the impurity induced twinning (IIT). Changes in the dynamic microhardness of the samples were mainly determined by the size of Si phases. Addition of vanadium led to quite lower elastic modulus in the vanadium added alloys compared to base alloy. © 2014 Elsevier B.V.
Nanoindentation study on Gd-deposited YBaCuO superconductor
(2013-01-01) Yilmaz F.; Uzun O.; Kolemen U.; Kilicaslan M.; Basman N.; Ergen S.; Ozturk K.; Yanmaz E.
Nanoindentation technique was used to characterize the mechanical properties of Gd-deposited bulk YBaCuO superconductors fabricated by solid-state reaction method. In order to determine the hardness and reduced modulus of the samples, load-displacement data were analysed by using the Oliver-Pharr method. The hardness values exhibited significant peak load-dependence especially at lower peak loads, while the reduced modulus values were found to be nearly constant at studied loading range. In order to find true hardness of the samples, the peak load-dependency of hardness was analysed by using Meyer's law,minimum resistance model, elastic/plastic deformation model, energy balance model, Nix-Gao model and Mukhopadhyay approach. Of the aforementioned models, energy balance model and Mukhopadhyay approach were found to be the most effective models to explain the load-dependency of hardness. © Indian Academy of Sciences.
Structural and mechanical properties of hypereutectic AlSiFe powders and a new method for determination of sintering temperature
(2018-03-01) Ergen S.; Yılmaz F.; Gul S.; Kolemen U.; Kilicaslan M.; Uzun O.
In this study, the effect of Si amount on the microstructure, crystal structure and some mechanical properties of Al-(20,25,30 wt%)Si–5Fe powder mixtures produced by high energy ball milling method was investigated by determining the sintering temperature. In the X-ray diffraction analysis, no inter-metallic phases were found except for the Al, Si and Fe phases of the powder mixtures. The X-ray diffraction patterns were analyzed by the Rietveld method to determine amounts of the Al, Si and Fe elements in the powder mixtures. From the scanning electron microscopy analysis, it is seen that as the amount of Si increases, there is a marked decrease in the grain size of powders. In the micro-indentation tests performed at room temperature, the hardness and elastic modulus values of the pelletized powders were found to increase with the amount of Si. It was also found that the Al-20Si-5Fe powder mixture with the lowest Si content had the highest damping capability. The high temperature micro-indentation tests showed that the resulting Al-(20,25,30 wt%) Si-5 Fe powder mixtures started to consolidation at 200 °C and completed the consolidation at 400 °C. This method can be used as an alternative method in the determination of the sintering temperature of materials.