Structural and magnetic characteristics of Co-based amorphous powders prepared by wet mechanical alloying

• Co-based amorphous powder obtained by wet MA from elemental powder.
• The amorphous phase is thermally stable up to 420 °C.
• Powder saturation magnetisation decrease upon increasing milling time.
• The powder saturation magnetisation is recovered by annealing.

Amorphous soft magnetic powder of Co70Fe4Ni2Si15B9 (at.%) was obtained by wet mechanical alloying starting from elemental powders using benzene as process control agent (PCA). After 40 h of milling, full amorphisation of the powder was achieved as proved by XRD investigations. The evolution of the mean particle size and specific surface of the particles versus milling time was explained in the light of the phases evolutions and their specific properties. A decrease of the powder magnetisation was observed during its progressive amorphisation as a result of changes of the magnetic moments environment and the presence of benzene in the samples. According to DSC studies the amorphous powder present a two steps crystallisation leading to the formation of Co-fcc, Co2Si and Co2B phases. Annealing of the powder at 300 °C for 1, 2 and 3 h leads to a substantial increase of the saturation magnetisation.

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