Bulk soft magnetic materials from ball-milled Fe77Nb7B15Cu1 amorphous ribbons

The production of bulk amorphous and nanocrystalline samples with nominal composition Fe77Nb7B15Cu1 by compaction of ball milled amorphous melt-spun ribbons has been studied. The ribbons were pre-annealed at different temperatures, below and above the nanocrystallization onset. Powders were produced in a planetary mill, for various parameters such as the mass quantity in the vials, the ball-to-powder ratio and the milling time. Increased brittleness and coercivity reduction induced in the ribbons by pre-annealing treatment were examined. Hot-pressing consolidation has been used to obtain bulk materials. The influence of both compaction temperature and time on the magnetic properties of the compacted disks or toroids was also explored. The results indicate that the morphology of the powder is a key factor for the formation of bulk materials. Large particle size improves densification and magnetic softness. Post-annealing of bulk disks enhances the soft magnetic properties by reducing coercivity and enhancing saturation magnetization.