Browsing by Author "Saklakoglu N."
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Item Mechanical properties and microstructural evaluation of AA5013 aluminum alloy treated in the semi-solid state by SIMA process(2004) Saklakoglu N.; Saklakoglu I.E.; Tanoglu M.; Oztas O.; Cubukcuoglu O.The microstructure and mechanical properties of AA5013 aluminum alloys prepared by strain-induced melt activation (SIMA) process were studied to investigate the effects of cold working and heat treatment conditions. The specimens subjected to deformation ratios of 30 and 50% and various heat treatment time and temperature regimes were characterized in the present study. The results revealed that for the desired microstructure of the alloy, the optimum heat treatment temperature and time were 650°C and 60min, respectively, for both deformation ratios. However, the specimens with 50% cold working exhibited more brittle behavior while they contain finer grains with uniform distribution along the cross-sections as compared to 30% cold working. © 2004 Elsevier B.V. All rights reserved.Item Characterization of austenitic stainless steel after plasma immersion nitrogen and carbon implantation(Elsevier Ltd, 2007) Saklakoglu I.E.; Saklakoglu N.; Short K.T.; Collins G.A.It has been shown in the literature that plasma immersion ion implantation (PIII) can increase the wear resistance of austenitic stainless steel without losing its corrosion resistance. In this work, the effect of PIII treatment with C ions introduced into the chamber during the process on the tribological properties of AISI 316 L stainless steel has been studied and the results compared. © 2006 Elsevier Ltd. All rights reserved.Item The life of WC-Co cutting tools treated by plasma immersion ion implantation(2007) Saklakoglu I.E.; Saklakoglu N.; Ceyhun V.; Short K.T.; Collins G.In this study, the tool life of plasma immersion nitrogen-implanted cutting inserts while machining AISI 4140 steel has been investigated. The implantation time was 5 h and the temperature was in the range 320-520 °C. Implantation dose was ∼2×1018 ions cm-2 for all treatments. Surface topography of the implanted surfaces was obtained from atomic force microscopy. Results of the turning tests are discussed in terms of tool life (flank wear) and surface roughness of the workpieces. The results show that plasma immersion nitrogen implantation increased tool life by about 85%. © 2006 Elsevier Ltd. All rights reserved.Item Sliding wear behaviour of Zr-ion-implanted D3 tool steel(2007) Saklakoglu N.; Saklakoglu I.E.; Ceyhun V.; Monteiro O.R.; Brown I.G.The wear and friction characteristics of zirconium-ion-implanted AISI D3 tool steel have been investigated using pin-on-disc methods. Ion implantation was carried out using a vacuum-arc-based ion implanter to form multicharged zirconium ion beams at a mean ion energy of 130 keV, and the implantation doses investigated were approximately 3.6×1016, 5×1016 and 1×1017 ions cm-2. It was found that Zr implantation decreased both the wear and the coefficient of friction. The beneficial effects of Zr implantation in terms of associated Auger electron spectroscopy, Rutherford backscattering spectroscopy and scanning electron microscopy microprobe analyses are described. © 2006 Elsevier Ltd. All rights reserved.Item Microstructural evolution of ETIAL 160 aluminium alloy feedstock produced by cooling slope casting(Trans Tech Publications Ltd, 2008) Saklakoglu N.; Birol Y.; Kasman Š.Owing to its superior flow and mould-filling capability, a fully globular structure is essential for semisolid processing technologies. The present work was undertaken to identify the cooling slope casting process parameters that, upon heating to the semisolid state, gives the required globular structure for the ETIAL 160 alloy. Of the two pouring temperatures investigated, 605 °C and 615 °C, the lower pouring temperature was found to provide more globular grains surrounded by liquid phases.Item Semisolid microstructure evolution during cooling slope casting under vibration of A380 aluminum alloy(2010) Gencalp S.; Saklakoglu N.This study is concerned with the influence of the vibration at a specific frequency to the inclined plate during cooling slope casting. A380 aluminum alloy was employed in the present work. The alloy was poured from the inclined plate with an angle of 60and a length of 500mm at a pouring temperature of 630C. The pouring was carried out on an inclined plate with and without vibration. Microstructures of specimens obtained from both conditions were examined. Grain size analysis of specimens was carried out. Experimental results showed that the application of vibration affected the microstructure. Hence, it was determined that the application of vibration increased the nucleation and led to more breaking of dendrite arms. In this study, the convection of melt by vibration played an important role on formation of non-dendritic primary Al-particles. Copyright © Taylor & Francis Group, LLC.Item Microstructural evolution and mechanical properties of cold-deformed al-5cu alloy samples after isothermal heat treatments(2010) Saklakoglu N.; Gencalp S.Abstract.In this paper, the microscopic morphology of a semi solid Al5Cu alloy by strain induced melt activated (SIMA) process were investigated, and the effects of predeformation, microstructural evolution, aging response and hardness changes were determined. The microstructural observation shows that while the grain boundaries started to appear after 620°C, globular grains surrounded wet boundaries needed for SSP were obtained at 650°C. The grain sizes exhibited ununiformity from the outer surface to the center of the sample because of ununiform predeformation. Although isothermal heat treatments reduced hardness, age hardening gave back the hardness loss. © 2010 American Institute of Physics.Item Formation of globular microstructure in A380 aluminum alloy by cooling slope casting(2011) Saklakoglu N.; Gencalp S.; Kasman S.; Saklakoglu I.E.Thixoforming and related semi-solid processing (SSP) methods require thixotropic materials. One of the many SSP techniques is the cooling slope (CS) casting process, which is simple and has minimal equipment requirements, and which is able to produce feedstock materials for semisolid processing. When the feedstock is reheated to the semisolid temperature range, nondendritic, spheroidal solid particles in a liquid matrix suitable for thixoforming are obtained. In this study, equipment for the CS technique was first established, and then the effects of the pouring temperature and inclined slope angle on the microstructures of A380 aluminum alloy (ISOAlSi8Cu3Fe) were studied. Optimum parameters for thixoforming experiments were selected, and it was found that the microstructure produced by the inclined plate depended on its angle and the pouring temperature. © (2011) Trans Tech Publications, Switzerland.Item The effects of cooling slope casting and isothermal treatment on wear behavior of A380 Alloy(2011) Saklakoglu N.; Gencalp S.; Kasman S.In this study, A380 aluminum alloy feedstock produced with cooling slope casting was exposed to isothermal treatment to obtain a globular microstructure which is a key feature for semisolid forming. The dendritic primary phase in the conventionally cast A380 alloy has readily transformed into a non-dendritic one in ingots cast over a cooling plate from pouring temperatures between 615, 630 and 650 °C. After the casting process, isothermal treatment was carried out at 565 °C in induction unit. Isothermal treatment yields a globular microstructure. To determine the tribological properties of this alloy, a pin-on-disc tribometer was used to carry out tribological tests under dry sliding conditions. The results showed that both cooling slope casting and isothermal treatment has an effect on tribological properties. © (2011) Trans Tech Publications, Switzerland.Item Effects of Low-Frequency Mechanical Vibration and Casting Temperatures on Microstructure of Semisolid AlSi8Cu3Fe Alloy(Springer Verlag, 2012) Gencalp S.; Saklakoglu N.This paper is concerned with the influence of vibration on the cooling slope casting and gravity casting. Mechanical vibration during cooling slope casting is a new technique. Also isothermal holding period of hypoeutectic Al-Si alloy to prepare semisolid slurry has been studied. The convection caused by the vibration during solidification had remarkable effects on the formation of spherical α-Al particles. The main vibration effects include evolution and increase of nucleation and thus reducing as-cast grain size; globularization of particles and production of a more homogenous metal structure. In this work, mechanical mould vibration and mechanical-inclined plate vibration was applied to an AlSi8Cu3Fe alloy at fixed frequency. Metallographic examinations and grain analysis were done on specimens obtained with different pouring temperatures and casting methods. The α-Al particles were spherical in cooling slope casting under vibration, as compared with cooling slope casting without vibration and gravity casting with vibration. A grain analysis along with different casting techniques was performed in order to understand the vibration effect. A heat-transfer mechanism seems responsible for the vibration effect in grain formation. © 2012 King Fahd University of Petroleum and Minerals.Item Influence of Ag content on microstructure and intermetallic phases of AlSi12 alloy(Maney Publishing, 2013) Turker A.; Saklakoglu N.The main objective of this study is to examine the influence of trace additions of silver on the morphology and composition of the complex microstructure of the intermetallic phases in AlSi12 alloy. lntermetallics were found in short or long rod, or 'Chinese Script', forms containing Si, Fe, Mn, Ag and Mg, These compounds became richer towards the grain boundaries. lt was observed that the high Ag content intermetallics were created in the form of short rods. ln all samples with added Ag, the dendritic structures had transformed into non-dendritic ones. The addition of Ag, in addition to the degeneration of the dendritic structures, enhanced the transformation from rosette form to globular morphologies. The results showed that the amount of eutectic Si increased with small additions of Ag to the AlSi12 alloy. lt was established that in general the Ag is distributed within the eutectic structure.©2013 W. S. Maney & Son Ltd.Item Characterization of microplastic deformation produced in 6061-T6 by using laser shock processing(2014) Gencalp Irizalp S.; Saklakoglu N.; Yilbas B.S.High dislocation densities are formed in the irradiated region of the workpiece during the laser shock processing; in which case, surface hardening is resulted. The process involves with recoil pressure loading at the workpiece surface with the minimum heating effects in the irradiated region. This favors the process to be a good candidate for the surface treatment of metallic materials. Therefore, in the present study, laser shock processing of 6061-T6 aluminum alloy is carried out and the influence of a number of laser pulses and irradiated spot diameter on the treated layer characteristics, including morphology and hardness, are investigated. It is found that the number of laser pulses has significant influence on the resulting surface characteristics such as surface roughness, crystallite size, micro-strain, and microhardness of the alloy. In this case, surface roughness is deteriorated by increasing number of laser pulses and pulse intensity. In addition, fine crystallite structure takes place in the laser-treated region. © 2013 Springer-Verlag London.Item Investigation of wear behaviour of thixoformed and conventional gravity cast AlSi8Cu3Fe alloys(2014) Saklakoglu N.; Irizalp S.G.; Ercayhan Y.; Birol Y.Purpose-In the present work, thixoformed AlSi8Cu3Fe alloy was investigated for its tribological properties. The tribological analysis reveals good sliding wear behaviour for thixoformed alloy due to thixotropic microstructural character. The results are compared with sliding wear behaviour of conventional gravity cast alloy. This paper aims to discuss these subjects. Design/methodology/approach-In this study, thixoforming and gravity casting methods are used to produce materials. The ball-on-disc CSM tribometer was used to carry out the tribological tests that were performed under dry sliding conditions, under two different loads of 1N and 5N. Wear tests were performed first on the conventional gravity cast samples and then on the thixoformed counterparts in exactly the same fashion to facilitate a comparison. The microstructural characterizations are performed in optical microscopy, scanning electron microscopy and energy dispersive X-ray spectrometry. Findings-Thixoformed samples have better wear resistance than conventional gravity cast samples. The wear performance improves in thixoformed AlSi8Cu3Fe alloy thanks to changing the microstructure. The superiority of the former is attributed to its structural features. Originality/value-In this study, the thixoforming of AlSi8Cu3Fe alloy can provide important wear performance in comparison with conventional casting of AlSi8Cu3Fe alloy. This alloy is known to be used widely in automotive industry. Therefore, the alloy is highly exposed to wear and it is thought that thixoforming method can increase the wear resistant. © Emerald Group Publishing Limited.Item Effect of Fe-rich intermetallics on the microstructure and mechanical properties of thixoformed A380 aluminum alloy(Elsevier B.V., 2014) Gencalp Irizalp S.; Saklakoglu N.The effect of α-Fe and β-Fe intermetallics concentration and morphology as well as α-Al morphology on the microstructure and mechanical properties of thixoformed and gravity cast A380 alloy was reported. The α-Al15Si2(Fe,Mn)3 intermetallic particle was observed polyhedral morphology in thixoforming while it was observed Chinese script morphology in conventional gravity casting. The β-Al5FeSi particle was solidified in the form of small plate in thixoforming while it was solidified in the form of needle-like in gravity casting at the grain boundaries of α-Al. The mechanical properties of the alloys have been enhanced by thixoforming compared with the conventional cast condition. © 2014 Karabuk UniversityItem Pulsed Nd: YAG laser shock processing effects on mechanical properties of 6061-T6 alloy(2014) Gencalp Irizalp S.; Saklakoglu N.; Akman E.; Demir A.The aim of this paper is to investigate effects of single and double shot Nd:YAG laser shock processing (LSP) on residual stress, micro-hardness and tensile properties of 6061-T6 aluminum alloy. The X-ray diffraction technique was used to measure surface residual stress in LSP-treated 6061-T6 samples. The magnitude and directional dependence of the surface residual stress after single shot and double shot LSP were investigated with the sin2 Ψ method. The results show that laser shock processing can significantly increase surface compressive residual stress. In addition, micro-hardness of the LSP-treated sample was measured using a Vickers diamond indenter depending on the depth. The tensile tests of the single shot and double shot LSP-treated and untreated samples were carried out by the Schimadzu tensile testing machine having a video extensometer. Experimental results show that the values of micro-hardness, tensile strength and uniform elongation increase by LSP. © 2013 Elsevier Ltd. All rights reserved.Item Near surface modification of aluminum alloy induced by laser shock processing(Elsevier Ltd, 2014) Saklakoglu N.; Gencalp Irizalp S.; Akman E.; Demir A.This paper investigates the influences of near surface modification induced in 6061-T6 aluminum alloy by laser shock processing (LSP). The present study evaluates LSP with a Q-switched Nd:YAG low power laser using water confinement medium and absorbent overlay on the workpiece. The near surface microstructural change of 6061-T6 alloy after LSP was studied. The residual stress variation throughout the depth of the workpiece was determined. The results showed an improvement of the material resistance to pit formation. This improvement may be attributed to compressive residual stress and work-hardening. The size and number of pits revealed by immersion in an NaOH-HCl solution decreased in comparison with the untreated material. © 2014 Elsevier Ltd.Item Laser shock processing of 6061-T6 aluminium alloy: Thermal modelling and analysis(Old City Publishing, 2016) Zafar H.; Saklakoglu N.; Irizalp S.G.; Khan S.; Shuja S.Z.; Boran K.; Yilbas B.S.Laser shock processing of 6061-T6 aluminium alloy is carried out. Temperature and stress fields are simulated in line with the experimental conditions. Metallurgical changes due to the laser shock and microhardness in the laser treated region are examined using analytical tools that include scanning and transmission electron microscopes and microhardness tester. The depth of shock affected region, plastic strain, and dislocation density are determined numerically and experimentally in the laser treated region. It is found that the temperature attains high values at the centre of the irradiated spot resulting in high rate of evaporation at the surface. The recoil pressure formed, due to high evaporation rate, at the laser treated surface results in plastic deformation of about 500 mm below the surface. A dislocation density of the order 2 × 1013 to 4 × 1013 cm-2 occurs in the surface region. Although high temperature gradients result in high stress levels in the region below the surface vicinity, high recoil pressure results in crack free surface with compressive stress. © 2016 Old City Publishing, Inc.Item High strength and high ductility behavior of 6061-T6 alloy after laser shock processing(Elsevier Ltd, 2016) Gencalp Irizalp S.; Saklakoglu N.The plastic deformation behavior of 6061-T6 alloy which was subjected to severe plastic deformation (SPD) at high strain rates during laser shock processing (LSP) was researched. In LSP-treated materials, the near surface microstructural change was examined by TEM and fracture surfaces after tensile testing were examined by SEM. An increase in strength of metallic materials brings about the decrease in ductility. In this study, the results showed that LSP-treated 6061-T6 alloy exhibited both high strength and high ductility. TEM observation showed that stacking fault (SF) ribbon enlarged, deformation twins formed and twin boundary increased in LSP-treated 6061-T6 alloy. This observation was an indication of stacking fault energy (SFE) decrease. Work hardening capability was recovered after LSP impacts. © 2015 Elsevier Ltd. All rights reserved.Item Laser peening of metallic materials(Elsevier Inc., 2017) Gencalp Irizalp S.; Saklakoglu N.Laser peening is a good candidate for the surface treatment industry because of its localized operation, very fast processing, and ability to use multiple types of radiation; therefore, it has recently become a process used for industrial production. The mechanical recoil impulse that arises from rapidly expanding vapor generates high pulse pressure, and the structure of the workpiece changes. In the laser peening process, no melting takes place and a shock wave is generated; compressive residual stresses are induced in the material surface. It is used primarily to increase the fatigue life and improve cracking resistance of engineering materials. Compared with the traditional shot peening process, laser peening creates a higher magnitude of deeper compressive residual stresses in component surfaces, therefore creating high fatigue resistance in metallic materials because these compressive residual stresses inhibit fatigue crack initiation and propagation. Laser peening also has a significant role in improving microstructure, surface morphology, hardness, strength, fatigue life, and corrosion resistance. Laser peening can be applied to a finished surface of a part or before the finishing step, and the process is applicable to a wide range of metals and alloys of titanium, aluminum, nickel, and steels. © 2017 Elsevier Inc. All rights reserved.Item Performance of Fe-based hardfacings on hot forging die: Experimental, numerical and industrial studies(Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, 2018) Saklakoglu N.; Irizalp S.G.; Dogan S.; Ildas G.; Saklakoglu I.E.This paper is an investigation into the use of Fe-based alloys as part of wear resistant hardfacing materials in AISI 1.2714 tool steel. Four different weld hardfacing alloys were deposited on 1.2714 steel substrates using tungsten inert gas welding (TIG) process. Wear tests were carried out using a pin-on-disc wear tester at room temperature. Microhardness and micrographs of the weld overlays were obtained. High-Temperature properties were estimated by numerical analysis. The phases of the hardfacings were obtained by XRD and also estimated by numerical analysis. The results from the laboratory tests were then compared with the results obtained from field studies. The results showed that some Fe-based alloys improved dies lifetime; others created poor surfaces. A Fe-based hardfacing alloy D which included high C with Cr, W, Mo had the best wear behavior among the weld overlays. © 2018 Institute of Materials and Machine Mechanics, Slovak Academy of Sciences. All rights reserved.