Synthesis and characterisation of nanostructured FeCo alloys

Abstract

Nanocrystalline Fe_(1−x)Co _x (x = 0.12, 0.5, 0.6) mixtures have been prepared by mechanical alloying using a planetary ball mill under several milling conditions. The alloying process between the elemental powders and the microstructure changes of the prepared samples have been investigated using X-ray diffraction (XRD) and ⁵⁷Fe Mössbauer spectrometry.

The XRD patterns refinement on the mechanical alloying products according to the Rietveld method (Maud software) reveals the allotropic transformation of Co from fcc to hcp form and the progressive dissolution of Co into the α-Fe lattice as a function of both Co concentration and milling conditions. The grain size values of the obtained powders reaches a nanometer scale of about 10 nm.

Mössbauer results show that the beginning of the solid state reaction between Fe and Co elemental powders depends on the milling conditions. After 24 h of milling, the average hyperfine magnetic fields values of Fe₈₈Co₁₂, Fe₅₀Co₅₀ and Fe₄₀Co₆₀ mixtures are consistent with a disordered and an ordered FeCo solid solution, respectively.