Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 40Citation - Scopus: 43The Role of Hydrogen in the Edge Dislocation Mobility and Grain Boundary-Dislocation Interaction in Α-Fe(Pergamon-Elsevier Science Ltd, 2021-09) Kapci, Mehmet Fazil; Schoen, J. Christian; Bal, Burak; Schön, J. ChristianThe atomistic mechanisms of dislocation mobility depending on the presence of hydrogen were investigated for two edge dislocation systems that are active in the plasticity of alpha-Fe, specifically 1/2<111>{110} and 1/2<111>{112}. In particular, the glide of the dislocation pile-ups through a single crystal, as well as transmission of the pile-ups across the grain boundary were evaluated in bcc iron crystals that contain hydrogen concentrations in different amounts. Additionally, the uniaxial tensile response under a constant strain rate was analyzed for the aforementioned structures. The results reveal that the presence of hydrogen decreases the velocity of the dislocations -in contrast to the commonly invoked HELP (Hydrogen-enhanced localized plasticity) mechanism-, although some localization was observed near the grain boundary where dislocations were pinned by elastic stress fields. In the presence of pre-exisiting dislocations, hydrogen-induced hardening was observed as a consequence of the restriction of the dislocation mobility under uniaxial tension. Furthermore, it was observed that hydrogen accumulation in the grain boundary suppresses the formation of new grains that leads to a hardening response in the stress-strain behaviour which can initiate brittle fracture points. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Article Citation - WoS: 13Citation - Scopus: 14The Effect of Strain Rate on the Hydrogen Embrittlement Susceptibility of Aluminum 7075(ASME, 2022-11-22) Baltacioglu, Mehmet Furkan; Cetin, Baris; Bal, BurakThe effects of changing the strain rate regime from quasi-static to medium on hydrogen susceptibility of aluminum (Al) 7075 were investigated using tensile tests. Strain rates were selected as 1 s(-1) and 10(-3) s(-1) and tensile tests were conducted on both hydrogen uncharged and hydrogen charged specimens at room temperature. Electrochemical hydrogen charging method was utilized and the diffusion length of hydrogen inside Al 7075 was modeled. Material characterizations were carried out by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) and microstructural observations of hydrogen uncharged and hydrogen charged specimens were performed by scanning electron microscope (SEM). As opposed to earlier studies, hydrogen embrittlement (HE) was more pronounced at high strain rate cases. Moreover, hydrogen enhanced localized plasticity (HELP) was the more dominant hydrogen embrittlement mechanism at slower strain rate but coexistence of hydrogen enhanced localized plasticity and hydrogen enhanced decohesion was observed at a medium strain rate. Overall, the current findings shed light on the complicated hydrogen embrittlement behavior of Al 7075 and constitute an efficient guideline for the usage of Al 7075 that can be subject to different strain rate loadings in service.Article Citation - WoS: 39Citation - Scopus: 44Fracture Behavior of Novel Biomedical Ti-Based High Entropy Alloys Under Impact Loading(Elsevier Science SA, 2021-01) Gurel, S.; Yagci, M. B.; Canadinc, D.; Gerstein, G.; Bal, B.; Maier, H. J.This paper focuses on the mechanical properties and fracture behavior of newly developed body-centered-cubic structured TiTaHfNb, TiTaHfNbZr and TiTaHfMoZr high entropy alloys (HEAs) under impact loading as part of an effort to evaluate their potential utility as implant materials. The experimental findings showed all three Ti based HEAs have lower Young's modulus as compared to the conventionally used implant materials. Fractography analysis revealed that the TiTaHfNb HEA demonstrated significant ductility with the highest energy absorption capacity, while the TiTaHfNbZr and the TiTaHfMoZr alloys exhibited mixed mode fracture with relatively low ductility. Specifically, the reduction of ductility and energy absorption capacity under impact loading was attributed to the addition of Zr and Mo into Ti-based HEA system, which facilitates formation of additional dislocations in the microstructure due to increased lattice distortion. The current findings demonstrate that, from a mechanical point of view, the TiTaHfNb HEA could be considered as an alternative implant material for applications demanding high wear and corrosion resistance, such as hip or knee implants, and thus, warrant further investigation of the biomedical performance of this alloy.YArticle Citation - WoS: 5Citation - Scopus: 7Experimental and Molecular Dynamics Simulation-Based Investigations on Hydrogen Embrittlement Behavior of Chromium Electroplated 4340 Steel(ASME, 2021-06-17) Dogan, Ozge; Kapci, Mehmet Fazil; Esat, Volkan; Bal, BurakIn this study, chromium electroplating process, corresponding hydrogen embrittlement, and the effects of baking on hydrogen diffusion are investigated. Three types of materials in the form of Raw 4340 steel, Chromium electroplated 4340 steel, and Chromium electroplated and baked 4340 steel are used in order to shed light on the aforementioned processes. Mechanical and microstructural analyses are carried out to observe the effects of hydrogen diffusion. Mechanical analyses show that the tensile strength and hardness of the specimens deteriorate after the chrome-electroplating process due to the presence of atomic hydrogen. X-ray diffraction (XRD) analyses are carried out for material characterization. Microstructural analyses reveal that hydrogen enters into the material with chromium electroplating process, and baking after chromium electroplating process is an effective way to prevent hydrogen embrittlement. Additionally, the effects of hydrogen on the tensile response of alpha-Fe-based microstructure with a similar chemical composition of alloying elements are simulated through molecular dynamics (MD) method.