- Formation and Thermal Properties of Amorphous Ti40Cu40Ni10Al10 Alloy by Mechanical Alloying
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Hyun-Goo Kim
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J Korean Powder Metall Inst. 2009;16(5):363-369.
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DOI: https://doi.org/10.4150/KPMI.2009.16.5.363
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 Abstract
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- The amorphization process and the thermal properties of amorphous Ti_40Cu_40Ni_10Al_10 powder during milling by mechanical alloying were examined by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The chemical composition of the samples was examined by an energy dispersive X-ray spectrometry (EDX) facility attached to the scanning electron microscope (SEM). The as-milled powders showed a broad peak (2theta = 42.4°) with crystalline size of about 5.0 nm in the XRD patterns. The entire milling process could be divided into three different stages: agglomeration (0 < t_m ≤ 3 h), disintegration (3 h < t_m ≤ 20 h), and homogenization (20 h < t_m ≤ 40 h) (t_m: milling time). In the DSC experiment, the peak temperature T_p and crystallization temperature T_x were 466.9°C and 444.3°C, respectively, and the values of T_p, and T_x increased with a heating rate (HR). The activation energies of crystallization for the as-milled powder was 291.5 kJ/mol for T_p.
- Chemical Leaching of Non-Equilibrium Al(Fe-Co) Powder Produced by Rod Milling
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Hyun-Goo Kim
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J Korean Powder Metall Inst. 2003;10(5):305-309.
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DOI: https://doi.org/10.4150/KPMI.2003.10.5.305
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Abstract
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- We report on the formation and chemical leaching of non-equilibrium Al_0.6(Fe_75Co_25) alloy produced by rod milling. X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry, scanning electron microscopy, and vibrating sample magnetometry were used to characterize the as-milled and leached specimens. After 400 h, only the Al_0.4Fe_0.6 peak of the body-centered cubic type was present in the XRD pattern. The entire rod milling process could be divided into three different stages of milling: agglomeration, disintegration, and homogenization. The saturation magnetization, M_s decreased with increased milling time, the M_s of the powders before milling was about 113.8 emu/g, the M_s after milling for 400 h was about 11.55 emu/g. Leaching of the Al in KOH of the Al at room temperature from the as-milled powders did not induce any significant change in the diffraction pattern. After the leached specimen had been annealed at 600°C for 1 hour, the nanoscale crystalline phases were transformed into the bcc Fe, cubic Co, and CoFe_2O_4 phases. On cooling the specimen from 850°C, the degree of magnetization increased slightly, then increased sharply at approximately 364.8°C, indicating that the bcc Al_0.4Fe_0.6 phase had been transformed to the Fe and Co phases.
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