Makale

Permanent URI for this community

https://kurumsalarsiv.tenmak.gov.tr/handle/20.500.12878/6

Browse

Browsing Makale by Publisher "ELSEVIER"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    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.
  • Thumbnail Image
    Item
    Influence of calcination conditions on deep eutectic solvents (DES) leaching efficiency of light rare earth elements in bastnasite ore
    (ELSEVIER, 2024-11-02) Kaplan, S. Samet; Kurtulan, Cisem Celik; Gurmen, Sebahattin; Orhan, Gokhan; Sonmez, Mehmet Seref
    In this century, our daily life is surrounded by technological devices, and Rare Earth Elements (REE) are at the heart of this technological revolution. They are always listed having the highest supply risk in critical minerals published by different countries. From that point of view, their extraction, and creating a secured supply chain is always crucial. In this research, the influence of calcination conditions on REE extraction from bastnasite ore was studied. Identical leaching in Ethylene Glycol (EG)-FeCl3 media which is one of the Deep Eutectic Solvents (DES) was applied to different calcines to understand calcination parameters on leaching efficiency. After conducting experiments created by Box-Behnken approach with different parameters of temperature, duration, and particles size, the highest Light Rare Earth Elements (LREE) extraction efficiency of 67.22 wt% was achieved at 900◦ C. However, while conducting control experiments, the highest extraction efficiency was found to be 75.986 wt% as a median of the experiments conducted at 500 ◦C during 180 min, and with particles finer than 25 µm. This efficiency increase with decreasing temperature is explained by Ce phase transformation from Ce2O3 to CeO2 as proved by XRD analysis. In addition to temperature, particle size was also found highly effective in extraction efficiency especially in Ce extraction. At the experiments conducted at 900 ◦C, and 270 min but with particles at different size ranges, Ce extraction dramatically dropped from 71.061 wt% to 9.587 wt% at the experiment conducted with finer particles. This lose in efficiency is directly correlated to increasing Ce phase transformation rate due to increasing surface area of fine particles. Non-calcined ore was also leached with DES, and only 10.977 wt% LREE could be extracted. Furthermore, it is concluded that calcination is of vital importance to transform the ore into a soluble form, and temperature, and particle size ranges are found to be two fundamental parameters for tuning the extraction efficiency.