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- 저자 : Sumanta Samal (검색결과 2 건)
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Priyanka Sahu,Sumanta Samal,Vinod Kumar 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.9
In this study, FeCoNi100-x(SiMn)x high entropy amorphous alloys (HEAAs) were successfully synthesized by mechanicalalloying. The structural, non-isothermal crystallization kinetics and magnetic characteristics were investigated by utilizingX-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy, differential scanning calorimetry,and vibrating sample magnetometer. The structural analysis revealed that a simple solid solution of β-BCC + ε-FCCphases was formed for x = 0.0, 0.1 whereas the evolution of the amorphous phase takes place along with the ε-FCC in the caseof x = 0.25, 0.5, 0.75, 1.0 HEAAs. The non-isothermal crystallization kinetics showed two distinct exothermic peaks: onset(Ex1, Ex2)and the apparent (Ep1, Ep2)activation energies calculated using Kissinger, Ozawa, and Augis-Bennett equations. This finding suggested that Ex1 > Ep1, Ex2 > Ep2 for the proposed HEAAs which confirmed that the nucleation process wasmore difficult than overcoming the energy barrier for the rearrangement of atoms and the grain growth process of crystallization. Furthermore, Friedman and Ozawa−Flynn−Wall models were used to calculate the local activation energies (Ea1,Ea2),which give consistent results with the apparent activation energies (Ep1, Ep2). In addition, Avrami exponents (n1, n2) and(Ψ1, Ψ2) were calculated by Johnson–Mehl–Avrami–Kolmogorov (JMAK) and Avrami-Ozawa combined approaches. Thisapproach revealed that the crystallization process becomes more accessible due to decreased local activation energies, leadingto high-dimensional growth with an increasing nucleation rate. Furthermore, the temperature-dependent magnetizationmeasurements showed a curie temperature below room temperature and fitted with Bloch and Curie–Weiss's law-modifiedmodel. The fitted results exhibited mixed phases, i.e., ferromagnetic and antiferromagnetic phases.
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Piyush Kumar,Reliance Jain,M. R. Rahul,Abhijit Ghosh,Sumanta Samal,Gandham Phanikumar 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.9
The present study explores the high temperature deformation behavior of FeCoNiCrAlTi dual phase high entropy alloy(henceforth referred to as DP-HEA) in the temperature range of 900–1100 °C (1173–1373 K) and the strain rate varyingfrom 0.001 to 0.1 s−1. The as-cast sample has been characterized using scanning electron microscopy, X-ray diffraction,and differential scanning calorimetry, which reveals the presence of two phases, disordered γ and ordered γ′. A constitutiverelationship between the process parameters (stress temperature, strain, and strain rate) has been drawn using the Arrheniustypeequation to recognize the high temperature deformation behavior of the DP-HEA. The optimum thermomechanicalprocessing window of the DP-HEA has been determined by constructing multiple contour maps based on different parameterssuch as efficiency, strain rate sensitivity, etc. And the optimum processing domain has been found to lie approximately in thetemperature range of 1260–1300 K and SR = 10–2.3–10–2 s−1, 1325–1373 K and SR = 10–1.4–10–1 s−1 & 1173–1193 K andSR = 10–1.3–10–1.55 s−1. Finally, the stable and unstable regimes in the processing maps are correlated with the microstructureof hot deformed samples.
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