Thermal evolution of the Ni3Fe compound obtained by mechanical alloying as probed by differential scanning calorimetry

An investigation of the formation of Ni3Fe soft magnetic material by high energy ball milling combining X-ray as well as neutron diffraction and differential scanning calorimetry (DSC) is presented. The Ni3Fe powders have been obtained by mechanical alloying of elemental powders in a planetary mill under argon atmosphere for milling times ranging from 2 h to 28 h. Ni3Fe intermetallic compound is obtained after 10–12 h of milling, as showed by X-ray and neutron diffraction and magnetic studies. The obtained crystallite has the mean size of 20 ± 2 nm after 28 h of milling. The DSC curves, recorded for different heating speeds, present a broad transformation reaction of the as-milled powders. The onset temperature of the transition is about 500 °C. The transition has been assigned to the re-crystallization of the nanocrystalline samples. The Curie temperature of Ni3Fe is also observed in the DSC curves, indicating the compound formation. DSC studies prove that the activation energy and the re-crystallization enthalpy increase with the milling time, as the compound is formed by milling and his grain size decrease.

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► Thermal evolution of Ni3Fe compound obtained by MA was studied by DSC.
► At low milling times both Ni3Fe formation and recrystallization occur during heating.
► Ni3Fe grains obtained by milling and Ni3Fe new germs produced during heating growth.
► Ni3Fe compound recrystallization enthalpy increases by increasing milling time.
► The activation energy of the recrystallization process has been calculated.