Browsing by Author "Kim, H. S."

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Addressing the strength-ductility trade-off in a thermomechanical-processed high entropy alloy
(Elsevier, 2023-12-15) Radi, Amin; Işıl, Canay; Seyedmohammadi, Seyedveghar; Kim, H. S.; Yapıcı, Güney Güven; Mechanical Engineering; YAPICI, Güney Güven; Radi, Amin; Işıl, Canay; Seyedmohammadi, Seyedveghar
High entropy alloys (HEAs) have garnered significant attention due to their exceptional mechanical behavior. However, the influence of secondary phases and dislocation substructures has yet to be thoroughly investigated. This study focuses on the incorporation of the decomposed η-phase within a face-centered cubic (FCC) microstructure at different recrystallization levels, aiming to achieve adequate ductility while maintaining strength at gigapascal levels. Various characterization techniques were employed to analyze the microstructure of both homogenized and annealed+aged conditions. Implementing a sub-micron grain size distribution and introducing a favorable dislocation substructure significantly enhanced the mechanical properties of yield strength, ultimate tensile strength, and ductility, reaching up to 1291 MPa, 1450 MPa, and 17.5%, respectively. The results highlight the influential role of grain size in facilitating the generation of geometrically necessary dislocations during plastic deformation.
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On the development of a novel multi-phase high entropy alloy with transformation-induced plasticity effect
(Elsevier, 2022-06-05) Radi, Amin; Asghari-Rad, P.; Kim, H. S.; Yapıcı, Güney Güven; Mechanical Engineering; YAPICI, Güney Güven; Radi, Amin
In the present work, microstructural evolution, and mechanical behavior of a novel high entropy alloy (HEA) are investigated through thermo-mechanical processing. The homogenized samples possess a single-phase cubic structure with high ductility. The rolled and subsequently annealed samples at various treatment conditions exhibit multi-phase microstructures. This study confirms that the sigma phase contribution becomes more significant on the mechanical response at higher annealing temperatures. Effects of phase distribution and degree of recrystallization on the microstructural evolution are examined in detail to probe the variation in the mechanical response. Samples subjected to annealing exhibit transformation-induced plasticity (TRIP) under plastic deformation. As such, the designed TRIP-assisted multi-phase HEA enables a combination of 1 GPa yield strength and about 10% of strain at failure.