Person: KENTLİ, AYKUT
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KENTLİ
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AYKUT
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Publication Metadata only Novel SPD Method: Twisted Variable Channel Angular Extrusion(KOREAN INST METALS MATERIALS) KENTLİ, AYKUT; Ozbeyaz, Kerim; Kaya, Hasan; Kentli, AykutDifferent types of SPD techniques are applicable and have been studied by various researchers. All of them have several advantages and disadvantages. Equal Channel Angular Pressing (ECAP) is one of the most popular SPD techniques and is still being developed. The aim of this paper is to improve the efficiency of ECAP process by putting forward a novel design (Twisted Variable Channel Angular Pressing (TV-CAP)) and also to achieve higher mechanical properties when compared to conventional ECAP processes. For this purpose, a new TV-CAP die was designed by combining three different methods: ECAP, Twist Extrusion, and Direct Extrusion. The new design was able to integrate the advantages of each method to the workpiece material. In this context, the design parameters of the TV-CAP die were first identified by finite element analysis (FEA) in Deform-3D. The TV-CAP die was produced according to the determined parameters and AA5083 alloy was pressed with this novel die. Hardness and tensile tests were carried out to compare mechanical properties. In addition, Optical Microscope, SEM, TEM images were taken, and XRD and EBSD analyses were carried out to examine the changes in grain structure. As a result of this experimental study, an increase of 197.3% was observed in the hardness value and an increase of 144.7% was achieved in the tensile strength value by using the novel TV-CAP die. These results also agreed with the effective strain values obtained from the FEA.Publication Open Access A new severe plastic deformation method: thin-walled open channel angular pressing (TWO-CAP)(SPRINGER LONDON LTD, 2020-01) KENTLİ, AYKUT; Sahbaz, Mehmet; Kaya, Hasan; Kentli, AykutIn this study, a novel severe plastic deformation method, named as thin-walled open channel angular pressing (TWO-CAP), was developed and applied to AZ31 magnesium alloy beams in U-type cross-sectional shape. First of all, the principles of the method with all parameters were determined, and the analytical model of the system was generated, and then the study was supported with the numerical analysis. Then, a proper experimental setup was established by considering theoretic outputs. After that, AZ31 magnesium alloy specimens were machined from bulk material in U-type shape as to fit the die channel, and then these specimens were annealed and pressed along the TWO-CAP die. Following the experimental studies, the specimens were tested in order to define the changes in mechanical and microstructural properties. In this stage, the tension test and hardness test were applied to determine the mechanical properties, while optical microscope, scanning electron microscope, energy dispersive spectrometry, X-ray diffraction, and transmission electron microscope analyses were applied to see the changes in microstructure. As a result, an improvement on strength, hardness, and toughness was observed depending on the changes on the microstructure and grain refinement due to the large plastic deformation.Publication Metadata only Performance of Novel TWO-CAP (Thin-Walled Open Channel Angular Pressing) Method on AA5083(KOREAN INST METALS MATERIALS, 2021) KENTLİ, AYKUT; Sahbaz, Mehmet; Kentli, Aykut; Kaya, HasanNewly developed severe plastic deformation (SPD) method TWO-CAP was applied to AA5083 to increase its mechanical properties. The method was developed to obtain the structural beams which have a thin-walled open-cross section area in high strength to weight ratio. During the TWO-CAP process, the annealed U-profile specimens will be pressed along the specifically designed die channel with the help of the hydraulic press machine. After the expansion and narrowing processes, the specimen leaves the die with initial dimensions at the end of each pass. Therefore, the material gains strength, hardness, and toughness while the microstructure of the material was improved as a result of the SPD. In order to determine the effect of the TWO-CAP on the mechanical properties of the material, the hardness and tension tests were carried out on the all passed specimens. Also, the characteristic investigations were performed on the specimens by using optical microscopy, SEM-EDS, and XRD analyses. Graphic AbstractPublication Metadata only INVESTIGATION OF STRAIN INHOMOGENEITy IN HExA-ECAP PROCESSED AA7075(POLSKA AKAD NAUK, POLISH ACAD SCIENCES, INST METALL & MATER SCI PAS, 2021) KENTLİ, AYKUT; Ogut, Serkan; Kaya, Hasan; Kentli, Aykut; Ozbeyaz, Kerim; Sahbaz, Mehmet; Ucar, MehmetSevere Plastic Deformation (SPD) techniques have been used by researchers for last three decades in order to obtain UltraFine Grained (UFG) materials. Equal Channel Angular Pressing (ECAP) is preferred more than other SPD techniques thanks to its high performance and practicability. Hexa Equal Channel Angular Pressing (Hexa-ECAP) - modified ECAP technique which enables to apply ECAP routes for cylindrical samples properly - was preferred in this study. Within the objective of this study, the effects of coefficient and ram velocity on the mean effective strain and strain inhomogeneity of Hexa-ECAP processed Al7075 aluminium alloy were investigated. Also, the effects of ram velocity and friction coefficient on hardness homogeneity were investigated benefitting from the similarity between the hardness distribution and the strain distribution.Publication Metadata only Applying hybrid equal channel angular pressing (HECAP) to pure copper using optimized Exp.-ECAP die(SPRINGER LONDON LTD, 2021) KENTLİ, AYKUT; Ogut, Serkan; Kaya, Hasan; Kentli, Aykut; Ucar, MehmetEqual channel angular pressing (ECAP), expansion equal channel angular pressing (Exp.-ECAP), and hybrid equal channel angular pressing (HECAP) or (Hybrid ECAP) processes were applied to pure copper specimens within this study. After the application of ECAP, the die used in the application of the Exp.-ECAP process was optimized considering the strain inhomogeneity in the specimen and the maximum load that occurred during the process. Finite element method (FEM), artificial neural network (ANN), and genetic algorithm (GA) were utilized together for the optimization process. The optimized die equally minimizes the pressing load and the strain inhomogeneity that occurred in the specimen. Using the optimized die, Exp.-ECAP and HECAP processes were applied to pure copper. The Exp.-ECAP process was previously applied only for aluminum alloys and magnesium alloys. With the application of the Exp.-ECAP process to pure copper, this gap in the literature was removed. In addition, with the application of the HECAP process, the effects of the Exp.-ECAP passes applied after ECAP were also examined which was not done earlier. The specimens, on which ECAP, Exp.-ECAP, and HECAP processes were applied, were subjected to microstructure analysis and mechanical tests, and the effects of these processes were examined. The results obtained showed that the Exp.-ECAP process gave better results in grain refinement and mechanical properties. The Exp.-ECAP passes applied after the ECAP process within the scope of the HECAP process provided a more homogeneous distribution for the microstructure and the hardness.