Milling and subsequent thermal annealing effects on the microstructural and magnetic properties of nanostructured Fe90Co10 and Fe65Co35 powders

The influence of milling and subsequent annealing on the microstructural and magnetic properties of Fe90Co10 and Fe65Co35 alloys is investigated. After milling for 8 h a body-centred cubic nanostructured Fe–Co alloy forms with an average crystallite size of about 12 nm. The magnetization saturation (MS) increases ∼16% for Fe65Co35 and 5% for Fe90Co10 alloys by milling for 8 h. Subsequent annealing of Fe90Co10 and Fe65Co35 powders for 105 min at 550 °C improves the MS about 6 and 11%, respectively. Before annealing, the coercivity increases (up to 60 Oe) by milling for 3 h, followed by a reduction on milling for longer periods (45 h). At the initial stage of the heating, a sharp decrease in HC to 8–10 Oe occurs due to the relief of internal strain. Further heating leads to an increase in the coercivity (intermediate times) followed by a slight diminution on heating for final stage.