Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Influence of Microstructure and Crystallographic Texture on Hydrogen Diffusion in If-Steel(Technical Faculty, Bor-serbia, 2023) Baskaya, U.; Uzun, R.; Davut, K.; Kilic, Y.; Gunduz, O.The relation between microstructure, crystallographic texture, and hydrogen diffusion was studied on a IF-steel. The steel samples were deep drawn to a strain level of 10%, 20%, 30% and 40% and then the hydrogen diffusion coefficients were determined using the Helios II system. Light optical microscope (LOM), scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) were used for microstructural characterization and crystallographic texture studies. The dependence of microstructural parameters was evaluated by Pearson correlation coefficient (PCC) values. These evaluations showed that local misorientations, crystallographic texture, and dislocation densityare interdependent. The PCC values show that grain size and dislocation density are the independent microstructure related parameters. These parameters were used to build a model to predict the hydrogen diffusion coefficient by multiple linear regression analysis. A sensitivity analysis was also performed with this model to understand to which parameter the hydrogen diffusion is most sensitive. The results of this analysis show that hydrogen diffusion is more sensitive to dislocation density, suggesting that dislocations are more effective trapping sites for hydrogen atoms. On the other hand, grain boundaries are less effective trapping sites since they also provide an additional diffusion mechanism.Article Citation - WoS: 5Citation - Scopus: 6Effect of Coiling Temperature on the Structure and Properties of Thermo-Mechanically Rolled S700mc Steel(Technical Faculty in Bor, 2022) Di Nunzio, P. E.; Cesile, M. C.; Oktay, S.; Davut, Kemal; Şeşen, M. K.The boron-free S700MC steel is usually produced by exploiting the properties of a ferrite-bainite mixed microstructure formed by coiling the strips at a temperature of about 450 degrees C, i.e.below the bainite starting temperature. With the aim of further enhancing the mechanical properties of 6 to 10 mm thick strips, industrial tests were carried out at a coiling temperature of 600 degrees C to promote the formation of a structure of ferrite and carbides, which is also acceptable for this type of steel. Unexpectedly, a microstructure composed of ferrite and martensite was obtained. Compared to the ferritic-bainitic grade, the new structure is characterized by a slight decrease of the yield point but by an increase of the ultimate tensile strength by no less than 80 MPa, with a transition from a quasi-discontinuous to a clearly continuous yielding behaviour. Accordingly, the ratio of yield strength to tensile strength decreases from 0.90 to 0.75 and the impact energy decreases by 35 J and 60 J for the two gauge levels, respectively. The mechanical behaviour of the strips coiled at high temperature is explained as a direct consequence of the dual phase structure with a hard phase interspersed in a soft ferrite matrix. The presence of martensite is explained by the so-called incomplete bainite reaction. The partial transformation into ferrite after coiling and the long time required for the coil to cool down stabilize the untransformed austenite due to the carbon enrichment making bainite formation at lower temperatures impossible.Article Citation - WoS: 3Citation - Scopus: 3Microstructural Characteristics of Mortars Prepared by Hot Lime Mix(Union of Croatian Civil Engineers and Technicians, 2020) Şerifaki, Kerem; Uğurlu Sağın, Elif; Böke, HasanThe effect of lime characteristics and hot lime mix method on hydraulic, microstructural and mechanical properties of mortars is determined by producing mortars from quicklimes of two different marbles and two limestones. Results of SEM-EDS, XRD and TGA analyses reveal that the porous microstructure of mortars and spongy texture of calcite crystals are the indicators of the hot lime mix method. This study shows that characteristics of limestones used for the production of limes, as well as the preparation method, directly affect hydraulic, mechanical and microstructural properties of mortars.Article Citation - WoS: 6Citation - Scopus: 3Anadolu’da Roma Dönemi Yapı Tuğlalarının Özellikleri(Gazi Üniversitesi, 2017) Uğurlu Sağın, ElifIn this study, chemical and mineralogical compositions, physical, microstructural and pozzolanic properties of Roman Period building bricks taken from Kizil Avlu (Serapeum) in Pergamon and from several different buildings from ancient sites of Aigai and Nysa were determined by using XRF, XRD, FTIR, SEM-EDS and chemical analyses. Chemical compositions of bricks were evaluted by statistical analyses in order to identify whether or not these bricks were manufactured by using same natural raw material sources. Analyses results indicated that Roman period building bricks were manufactured by using calcium rich clay sources and fired at low temperatures (<900°C). Brick samples were mainly composed of quartz, albite, anorthite, muscovite and hematite. Statistically significant differences found in their chemical compositions revealed that local raw material sources were selected for the manufacturing of historic brick samples belonging to different cities.