Yazar "Tigli, Ahmet" seçeneğine göre listele

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    Öğe
    A356 alüminyum alaşımının dökümünde katılaşma zamanı ve Nb ilavesinin mikroyapıya etkisinin incelenmesi
    (2024) Yalçın, Önder; Tokatlı, Mehmet; Tigli, Ahmet; Colak, Murat
    Alüminyum alaşımları hafiflik, korozyon direnci, elektrik ve ısı iletkenliğinin yüksek olması yüksek dayanım, sünek olması gibi özelliklerinde dolayı oldukça önemli bir mühendislik malzemesidir. Bu sebeple; otomotiv, havacılık, savunma, uzay endüstrisi, makine imalat, gıda endüstrisi gibi birçok alanda yaygınca kullanım bulmaktadır. Özellikle otomotiv sanayi ve yüksek teknoloji gereksinimi olan birçok sektörde kullanımı artmakla birlikte kalite gereksinimleri de artmaktadır. Alüminyum döküm alaşımlarından kalite beklentisindeki artışa bağlı olarak farklı alaşım elementi ilaveleri ile dökümler yapılması ve üretimde yeni teknoloji kullanımları üzerinde çalışmalar devam etmektedir. Bu çalışmada A356 alüminyum döküm alaşımına %0.03, %0.06 ve %0.1 Niyobyum ilavesinin değişen kesitler içeren kokil kalıba dökümünde mikroyapı üzerindeki etkileri incelenecektir. Çalışmada ergitme, sıvı metal temizleme, kokil kalıba döküm, metalografik numune hazırlama, mikroyapı inceleme ve imaj analiz teknikleri kullanılmıştır. Sonuçlar incelediğinde katılaşma zamanına ve Nb ilave miktarına bağlı olarak döküm mikro yapılarında değişimler olduğu gözlenmiştir.
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    Öğe
    Determination of effect of hydrogen on strength of aluminum by MD simulation
    (Springer Heidelberg, 2022) Tigli, Ahmet; Sahin, Hayati; Dizdar, Kerem Can; Dispinar, Derya
    The determination of types of defects that may be present in aluminum alloys has been a long-going discussion. Porosity has been held responsible for many of the failures in cast aluminum alloys. Due to the dramatic decrease in the solubility of hydrogen from liquid to solid aluminum, hydrogen is believed to be released from the solidification front and nucleate to form porosity. In this work, the diffusivity of hydrogen at different temperatures were investigated by means of Molecular Dynamic (MD) simulations. Dislocation density, crystal lattice deformation, and related changes in the tensile properties were determined in the presence of hydrogen for mono and nanocrystalline aluminum structures. The findings were correlated with the experimental and simulation data found in the literature where different tensile results were reported at different casting conditions.
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    Öğe
    Dodecagonal Zinc Oxide (d-ZnO) Monolayer for Water Desalination and Detection of Toxic Gases
    (Amer Physical Soc, 2023) Abdullahi, Yusuf Zuntu; Tigli, Ahmet; Ersan, Fatih
    Nanoporous materials have attracted great interest because of their variety of applications in nanodevices, such as gas storage, low-density magnetic storage, energy storage, supercapacitors, catalysis, membranes, etc. The most common purpose of using nanoporous materials is to make a material much lighter while preserving or improving the high structural stability of these compounds. In this work, we propose a two-dimensional dodecagonal zinc oxide (d-ZnO) monolayer via first-principles calculations based on density-functional theory (DFT). Our extensive analysis shows that this semiconducting porous d-ZnO material is mechanically, dynamically, and thermally stable and suitable for various applications, such as water membrane and gas detection at room temperature and above. We study the water permeability and Na+ and Cl- ions' rejection of d-ZnO material via conducting DFT and molecular dynamics (MD) simulations. Our simulations show that the energy barrier of the water molecule and Na+/Cl- ions passing through the porous d-ZnO structure is low and high, respectively. In addition, MD calculations show that the water permeability performance of d-ZnO material is high enough to use this material for water desalination applications. For further investigations, the detection of some selected gases (CO, SO, NO, CO2, SO2, and NO2) are investigated on d-ZnO and find that NO2, and SO2 would preferentially be detected on the d-ZnO substrate due to their high adsorption energy values as compared to physisorption
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    Öğe
    The effect of cooling plate, mechanical vibration, and grain refinement on the microstructure and hardness of A380 produced by sand mold
    (Taylor & Francis Ltd, 2024) Uslu, Emin; Tigli, Ahmet; Colak, Murat
    The mechanical properties of aluminium alloys can be increased by controlling the grain size and morphology of the alloy. In these studies, mechanical vibration, cooling slope plate (CSP), and grain refiner were applied on sand mould casting using A380 alloys. The hardness, and microstructure of the cast samples are investigated. These processes lead to the refinement of grain structures and a decrease in the tendency for dendritic structure formation. The Effect of the solidification time (modulus) on the microstructure is investigated. It was determined that the solidification time varies depending on the section thickness, which affects the SDAS values. It was observed that the lowest SDAS values were in CSP and the highest values were in grain refiners added casting. The lowest hardness value was recorded at CSP casting. Meanwhile, the grain refiner added vibration casting exhibits the highest hardness.
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    Öğe
    Water-aluminum reaction by MD simulations and its interpretation defect formation
    (Elsevier, 2023) Tigli, Ahmet; Dispinar, Derya
    Many of the aluminum and its alloys are produced by casting methods. During casting, aluminum is heated to temperatures above melting point. In the liquid state, aluminum reacts with water vapor to form aluminum oxide on the surface and hydrogen is dissolved in the melt. These are the two most critical defects that deteriorate the properties of the cast part. Therefore, it is important to investigate the possible reactions of water vapor with liquid aluminum in order to understand the formation of these defects. In this work, Molecular Dynamic (MD) analysis was used to evaluate the reactions of water vapor with aluminum at various temperatures (300, 500, 700, 900 and 1100 K). It was found that when aluminum reacts with water vapor, aluminum oxide layers form on the surface of the aluminum block. In addition, mono and di-atomic hydrogen are released due to the reaction between aluminum and water. These free hydrogen atoms are distributed homogeneously and rapidly in the aluminum block and gap between two aluminum blocks.