Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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  • Conference Object
    Formation and Stability of Hydrides During Hydrogenation of Ndfeb Magnets
    (Springer international Publishing Ag, 2025) Lazou, Adamantia; Tanriverdi, Hakan; Gokelma, Mertol
    Demand for magnets has increased in the last decades due to their usage in the energy sector. One of the most common magnets used for applications such as electronic devices, wind turbines, etc. is Nd2Fe14B (NdFeB). Neodymium (Nd) is one of the critical elements listed by the EU, hence the efficient use and proper recycling of Nd-containing materials become of great interest. Hydrogen is commonly used during magnet production and some hydrogen-assisted recycling approaches were also reported. This study reports an analysis of formed hydrides during hydrogenation of NdFeB magnets at up to 400 degrees C. In addition to experimental results, thermochemical modeling was performed by using FactSage databases to discuss the effect of temperature and pressure on hydrogenation. The study showed that the stability of phases changes with the temperature and pressure which affects the hydrogen content of phases after hydrogenation.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 1
    Microstructural Evolution During Homogenization Heat Treatment of Aa 6063 Alloy in Batch and Continuous Furnaces
    (Springer international Publishing Ag, 2024) Obali, Akin; Gokelma, Mertol; Urk, Deniz Kavrar; Dogan, Murat; Gokce, Gokcen
    Homogenization heat treatment after casting is performed to eliminate the dendritic segregation and coarse eutectic intermetallic phases since they reduce the fracture toughness of aluminium alloys. By the homogenization treatment, ss-AlFeSi can be converted to more spherical alpha-AlFeSi particles. The ss -> a transition is crucial because the ss-AlFeSi particles cause a number of surface defects and limit the extrudability. Also, the rate of cooling in the homogenization furnace is one of the critical influencing factors on the size of the Mg2Si precipitates which affect the mechanical properties positively. In this study, billets of AA 6063 from the same cast were put through homogenization heat treatment by using batch-type and continuous furnaces. The solution, quenching, and aging heat treatment were applied to each sample. Microstructural characterization by SEM and the hardness test were conducted to understand the effects of the furnace type on the mechanical properties of aged AA 6063 aluminium.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 1
    Assessment of Separation and Agglomerationt Tendency of Non-Metallic Inclusions in an Electromagnetically Stirred Aluminum Melt
    (Springer international Publishing Ag, 2023) Li, Cong; Dang, Thien; Gokelma, Mertol; Zimmermann, Sebastian; Mitterecker, Jonas; Friedrich, Bernd
    Presence of non-metallic inclusions (NMIs) reduces surface quality and mechanical properties of aluminum products. The development of good NMIs removal practices relies on the understanding of inclusion behaviors with respect to separation and agglomeration particularly in the turbulent flow. In the scenario of electromagnetically induced recirculated turbulent flow, the concerned behaviors of inclusions with different sizes have rarely been investigated experimentally. In the presented study funded by AMAP Open Innovation Research Cluster, reference materials were prepared with uniformly distributed NMIs (SiC and MgAl2O4) via an ultrasoundinvolved casting route. Reference materials were charged into an aluminum melt where turbulent flow was promoted via electromagnetic force. Microscopical analysis shows non-significant agglomeration tendency of SiC, MgAl2O4, and TiB2 inclusion. Time-weight filtration curve, PoDFA, and Spark Spectrometer results suggest a strong dependence of separation rate on particle size. Analytical models were established to estimate the collision rate of particles and to evaluate separation probability of different sized particles.