Browsing by Organisation Author "Aksu, Erhan"

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    Achieving superior strength and ductility in oxide dispersion strengthened IN625 alloy produced by laser powder bed fusion
    (ELSEVIER, 2024-12-19) Demirci, Kadir Tuğrul; Özalp, Ali; Güner Gürbüz, Selen Nimet; Bükülmez, İlhan; Aksu, Erhan; Aydoğan, Eda
    In this study, a new grade of oxide dispersion strengthened (ODS) Inconel 625 (IN625) alloy having the composition of 0.3 wt% Y2O3 – 0.4 wt% Hf – IN625 has been developed and produced by laser powder bed fusion (L-PBF). Production parameters have been determined for standard and ODS IN625 alloys to yield >99.9% densification. Microstructural analyses reveal similar texture along <001> while a larger but homogenous strain distribution exist in ODS IN625. Nano-particles are determined to be mostly Y-Hf-O and Y2O3 with an average size of ~30 ± 18 nm and 2.2 ± 1.1x1013 m-2 areal fraction. Tensile tests at room temperature (RT) and 700 °C demonstrate superior mechanical properties of ODS-IN625, particularly at elevated temperatures. While the yield strengths of standard and ODS IN625 alloys are similar (~680 MPa), ductility of ODS IN625 is slightly larger at RT. However, the yield strength of ODS-IN625 increased by 7.4%, reaching ~580 MPa, compared to the standard IN625, which has a yield strength of ~540 MPa at 700 °C. More notably, the ductility of ODS IN625 shows a remarkable improvement, increasing from ~12% in the standard IN625 to ~22%, representing an increase of more than 80%. Detailed microstructural analyses on the fracture surfaces of the ODS IN625 alloys exhibit submicron dimples, as well as an extensive amount of dislocation loops, Lomer-Cortrel (L-C) locks, and stacking fault tetrahedra. Nano-oxides were determined to be responsible for the dislocation wall structure and dislocation distribution which in turn improves the mechanical properties. This study sheds light on tailoring the strength-ductility balance in IN625 alloys by introducing the nano-oxide particles and perceiving the mechanism of this improvement.
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    Nuclear and Analytical Analysis Techniques That Primarily Used to Characterization of Ancient and Historical Materials
    (Springer, 2026-04-02) Kantoğlu, Ömer; Kalayci, Yakup; Aydin, Büşra; Çantay, Eren; Ergun, Ece; Bulduk Akkuş, Emel; Mert, Yüksel; Kirkayak, Özgü; Gökalp, Metin; Aksu, Erhan; Gündoğdu, Gençay
    Cultural artifacts, from ancient manuscripts to historic artworks, are vital symbols of national heritage and identity. The characterization of ancient artifacts is crucial for applying best practices in history and archaeology, including conservation, preservation, investigation, and the prevention of illegal trade. The illicit trafficking of these invaluable objects poses a significant threat to cultural preservation. The effective repatriation of stolen or illicitly exported cultural artifacts heavily relies on non-destructive methods, such as various nuclear and analytical techniques. These methods are critical not only for verifying the authenticity of the artifacts but also for establishing their provenance and legal ownership. This chapter explores the importance of analytical methods in the repatriation process applied in all over the world, highlighting their impact on the successful return of cultural treasures to their rightful owners.