Person: KENTLİ, AYKUT
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KENTLİ
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AYKUT
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Publication Metadata only Microstructure development and mechanical behaviour of pure copper processed by the novel TWO-CAP procedure(2023-01-01) KENTLİ, AYKUT; ÖĞÜT, SERKAN; KAYA H., UÇAR M., Ş Ahbaz M., KENTLİ A., Özbeyaz K., ÖĞÜT S.In this study, thin-walled open channel angular pressing (TWO-CAP) technique was applied to pure copper specimens as a novel severe plastic deformation (SPD) method. The TWO-CAP process was applied to the specimens up to four passes. After each pass, the microstructural and mechanical characterization of the material was investigated by tensile and hardness tests along with OM, SEM, EDS, TEM and XRD analyses. As a result, a highly increase in the mechanical properties was obtained, in addition satisfactory grain refinement was observed in microstructures. Strength and hardness values were positively affected from the minimizing the grain sizes after TWO-CAP process. Another reason of the improvements in mechanical properties can be explained as the increase in dislocation density. Furthermore, the effect of the TWO-CAP process on the dislocation density of the material has been demonstrated by XRD and TEM analyses in nanoscale. Moreover, the strain equation has been developed analytically and the effect of each pass on strain was calculated. Finally, the effect of the process on the stress-strain properties of the material was examined by the numerical analysis method and the study was verified.Publication 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.Publication Metadata only Comparison of the Effect of Equal Channel Angular Pressing, Expansion Equal Channel Angular Pressing, and Hybrid Equal Channel Angular Pressing on Mechanical Properties of AZ31 Mg Alloy(SPRINGER) KENTLİ, AYKUT; Ogut, Serkan; Kaya, Hasan; Kentli, AykutIn this study, Hybrid Equal Channel Angular Pressing (Hybrid ECAP) method was obtained by applying Equal Channel Angular Pressing (ECAP) and Expansion Equal Channel Angular Pressing (Exp.-ECAP) methods successively. These three angular pressing methods were applied to AZ31 Mg alloy using the same process parameters. First, AZ31 Mg specimens were produced in accordance with ECAP, Exp.-ECAP, and Hybrid ECAP dies. Then, changes in the microstructure of the processed specimens were examined using optical microscope, scanning electron microscope, energy dispersive spectrometry, transmission electron microscope, and x-ray diffraction methods. Besides, changes in the mechanical properties of the processed specimens were observed by performing hardness and tensile tests. As a result of the study, it was found that the Exp.-ECAP method provided higher increase in mechanical properties with more homogeneous microstructure and hardness distribution than the ECAP method. Additionally, the obtained Hybrid ECAP method continued to increase the mechanical properties of the alloy and made the microstructure and hardness distribution more homogeneous than the ECAP method.