Thermal and magnetic behavior of a nanocrystalline Fe(Ni, Co) based alloy

A nanocrystalline alloy of Fe51Co20Ni14Zr6B9, was produced by mechanical alloying. The main structural analysis was carried out via X-ray diffraction. The spectra were analyzed by Rietveld refinement using the MAUD program. The as-milled, 10, 20, 40 and 80 h alloys consisted primarily of metastable bcc-Fe(Co, Ni) nanocrystals reaching around 8 nm mean diameter, after 80 h. The morphology was examined via SEM and composition by ICP and EDX. Results show a slight (<1.5 at.%) contamination from milling tools. Differential scanning calorimetry data reveal broad hump between 100 and 450 °C associated with the relief of internal stresses. The exothermic peaks over 450 °C correspond to the crystallization related initially to the crystalline growth of the bcc-Fe(Co, Ni) phase and to the formation of fcc-(Fe, Ni, Co) and (Fe, Ni, Co)2B phases at higher temperatures. Frequency-dependent AC-susceptibility on the 80 h alloy confirms the presence of nanoparticles displaying a wide distribution of sizes favoring the existence of disordered magnetic interactions among them through the nanoparticle boundaries.