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Article Citation - WoS: 10Citation - Scopus: 10Determination of Mechanical Properties of Bi12tio20< Crystals by Nanoindentation(Elsevier Sci Ltd, 2022) Isik, M.; Gasanly, N. M.; Rustamov, F. A.Bi12TiO20 (BTO) single crystal was grown by Czochralski method and investigated mechanically by nano-indentation measurements. X-ray diffraction pattern of the crystal presented one intensive peak around 37.95 degrees associated with (330) plane of cubic crystalline structure. Nanoindentation experiments were performed at various loads between 5 and 100 mN. Hardness and Young's modulus of the crystal were determined by Oliver-Pharr method. The hardness-load dependency exhibited behavior of indentation size effect. True hardness value of BTO crystal was revealed as 4.4 GPa. Young's modulus decreased with increase of load and load-independent Young's modulus was found around 93 GPa at high loads. The load-dependent elastic and plastic deformation components were calculated and it was observed that the dominant component in BTO single crystal is plastic deformation at the applied loads. The present paper reports for the first time the mechanical characteristics of the BTO single crystal by carrying out nanoindentation experiments.Article Citation - WoS: 123Citation - Scopus: 135Wire arc additive manufacturing of high-strength low alloy steels: study of process parameters and their influence on the bead geometry and mechanical characteristics(Springer London Ltd, 2020) Yildiz, Ahmet Suat; Davut, Kemal; Koc, Baris; Yilmaz, OguzhanAdditive manufacturing (AM) is becoming increasingly popular since it offers flexibility to produce complex designs with less tooling and minimum material at shorter lead times. Wire arc additive manufacturing (WAAM) is a variant of additive manufacturing which allows economical production of large-scale and high-density parts. The WAAM process has been studied extensively on different steels; however, the influence of process parameters, specifically wire feed speed (WFS), travel speed (TS), and their ratio on bead geometry, microstructure, and mechanical properties, are yet to be studied. The present work aims at closing this gap by using the WAAM process with robotic cold metal transfer (CMT) technology to manufacture high-strength structural steel parts. For that purpose, single-bead welds were produced from HSLA steel by varying WFS between 5 and 10 m/min and the WFS to TS ratio between 10 and 20. Those variations produce heat inputs in the range of 266-619 J/mm. The results have shown that the wire feed speed to travel speed ratio is the major parameter to control the heat input. Increasing heat input increases characteristic bead dimension, whereas it reduces the hardness. In the second part of experiments, two single-bead walls were deposited via the parallel deposition strategy and one multiple-bead wall was produced using the oscillation strategy. The tensile properties were tested along two directions: parallel and perpendicular to deposition directions. For the yield strength and tensile strength, the difference between horizontally and vertically tested specimens was smaller than the standard deviations. On the other hand, the total and uniform elongation values exhibit up to 10% difference in the test direction, indicating anisotropy in ductility. Those tensile properties were attributed to repeated thermal cycles during the WAMM process, which can cause heat transfer in multiple directions. The yield strength of the multiple-bead wall produced via oscillation was lower, whereas its ductility was higher. The tensile properties and hardness differences were found to correlate well with the microstructure.Article Citation - WoS: 9Citation - Scopus: 10Characterization of Properties of Vanadium, Boron and Strontium Addition on Hpdc of A360 Alloy(Elsevier Science Sa, 2021) Gursoy, Ozen; Colak, Murat; Tur, Kazim; Dispinar, DeryaThe demand for lighter weight decreased thickness and higher strength has become the focal point in the automotive industry. In order to meet such requirements, the addition of several alloying elements has been started to be investigated. In this work, the additions of V, B, and Sr on feedability and tensile properties of A360 has been studied. A mold design that consisted of test bars has been produced. Initially, a simulation was carried out to optimize the runners, filling, and solidification parameters. Following the tests, it was found that V addition revealed the highest UTS but low elongation at fracture, while B addition exhibited visa verse. On the other hand, impact energy was higher with B additions.Article Citation - WoS: 8Citation - Scopus: 8The Investigation of Electronic Nature and Mechanical Properties Under Spin Effects for New Half-Metallic Ferromagnetic Chalcogenides Ag3crx4< (x = S, Se, and Te)(Elsevier, 2021) Erkisi, Aytac; Yildiz, Bugra; Wang, Xiaotian; Isik, Mehmet; Ozcan, Yusuf; Surucu, GokhanThis study presents the electronic and mechanical characteristics of ternary silver-based Ag3CrX4 (X = S, Se, and Te) chalcogenides having simple cubic crystalline structure (SC), conforming P4-3m (space group: 215) that are studied under the spin-polarized Generalized Gradient Approach (GGA) within the framework of the Density Functional Theory (DFT). The stable magnetic phase has been determined as the ferromagnetic (FM) phase for all studied systems. Then, phase stability, mechanical, thermal and electronic characteristics of Ag3CrX4 chalcogenides have been reported. In the calculated spin polarized electronic band structures for Ag3CrX4 chalcogenides, as an indicator of half-metallic behavior, metallicity has been observed in the majority spin channel, while indirect band gaps (1.04 eV for Ag3CrS4, 1.10 eV for Ag3CrSe4, and 1.25 eV for Ag3CrTe4) have been determined in the minority spin channel. Moreover, Ag3CrX4 chalcogenides have been found as thermodynamically stable and structurally synthesizable considering the calculated negative formation enthalpies. Elastic constants of studied chalcogenides satisfying Born-Huang criteria's pointed out the mechanical stability of materials. The predicted mechanical properties determined with elastic constants revealed that Ag3CrX4 chalcogenides belong to soft and ductile material family.
