Browsing by Author "Hadjipanayis, George C."
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Item Assessment of Directionally Solidified Eutectic Sm–Fe(Co)–Ti Alloys as Permanent Magnet Materials(IEEE Transactions on Magnetics, 2023-05-29) Gabay, Alexander M.; Han, Chaoya; Ni, Chaoying; Hadjipanayis, George C.Sm–Fe–Ti and Sm–Fe 0.8 Co 0.2 –Ti alloys were prepared via arc-melting and directionally solidified on a water-cooled copper hearth. The as-solidified alloys featured cells of the Sm(Fe,Co,Ti) 12 –Ti(Fe,Co) 2+δ –(α-Fe) lamellar eutectic. The lamellae of Sm(Fe,Co,Ti) 12 phase with a crystal structure of the ThMn12 type were less than 0.2 μm thick, and had their [001] easy-magnetization directions oriented along the temperature gradient of the solidification. The eutectic microstructure led to an increased coercivity, especially in the Co-added alloys. Below 250 °C, this coercivity was found not to vary much with temperature with a temperature coefficient of -0.18 %/°C. However, the modest absolute values, reaching only 0.7 kOe, are insufficient for utilization of the directionally solidified alloys as anisotropic permanent magnets.Item Bulk Mn-Al-C permanent magnets prepared by various techniques(AIP Publishing, 2016-03-01) Madugundo, Rajasekhar; Koylu-Alkan, Ozlem; Hadjipanayis, George C.; Rajasekhar Madugundo, Ozlem Koylu-Alkan, and George C. Hadjipanayis; Madugundo, Rajasekhar; Koylu-Alkan, Ozlem; Hadjipanayis, George C.Bulk Mn-Al-C magnets have been prepared by hot-compaction, microwave sintering and hot-deformation. Powders of Mn53.5Al44.5C2 alloy in the ε-phase produced by high energy ball milling have been used as precursor for the hot-compacted and microwave sintered magnets. Hot-deformed magnets were produced from alloy pieces in the τ-phase. The hot-compacted magnet exhibits magnetization, remanence and coercivity of 50 emu/g, 28 emu/g and 3.3 kOe, respectively. Microwave sintered magnet shows a maximum magnetization of 94 emu/g, remanence of 30 emu/g and coercivity of 1.1 kOe. The best magnetic properties are obtained in hot-deformed magnets with magnetization, remanence, coercivity and energy product of 82 emu/g, 50 emu/g, 2.2 kOe and 1.8 MGOe, respectively. Hot-deformed magnets exhibit texture with the highest degree of texture obtained 0.26. It is found that the pressure applied during compaction/deformation favors coercivity.