Microstructural and mechanical characterization of yttrium-modified high entropy alloys

Güven, Fatma Saadet
High entropy alloys (HEAs) have gained considerable attention recently due to their unique properties and a wide range of potential applications. This thesis focuses on the investigation of the structural and mechanical properties of high entropy alloys through the addition of yttrium, a rare earth element. This study aims to provide valuable information regarding the function of yttrium as an alloying element in developing high-performance materials. The design of HEAs and selection of the yttrium amount are made based on the thermodynamic calculations via computational methods of HEA Calculator and Thermo-Calc HEA database. HEA compositions of (CoCuFeNiMn)100-xYx (x = 0-5 at.%) are produced by arc melting followed by the suction casting technique. The effects of yttrium on the structural, microstructural, and mechanical properties of the HEAs are characterized comprehensively. X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy (SEM) are used to determine the crystal structure, phase composition, and microstructure of the yttrium-modified HEAs. The mechanical response of the alloys is examined by micromechanical and macro-mechanical methods, including microhardness measurements, nanoindentation analyses, and uniaxial compression tests. Comparative analyses are conducted between the micro alloyed HEAs and the base HEA composition to evaluate the effect of yttrium in the mechanical aspect. The findings indicate that yttrium addition improves the mechanical properties in terms of strength, hardness, and toughness compared to the base composition. The research outcomes contribute to a deeper understanding of HEAs and offer insights into the role of yttrium as a rare earth element in HEA systems.
Citation Formats
F. S. Güven, “Microstructural and mechanical characterization of yttrium-modified high entropy alloys,” M.S. - Master of Science, Middle East Technical University, 2023.