Milling and subsequent thermal annealing effects on the microstructural and magnetic properties of nanostructured Fe_(90)Co_(10) and Fe_(65)Co_(35) powders

摘要

The influence of milling and subsequent annealing on the microstructural and magnetic properties of Fe_(90)Co_(10) and Fe_(65)Co_(35) alloys is investigated. After milling for 8h a body-centred cubic nanostructured Fe-Co alloy forms with an average crystallite size of about 12 nm. The magnetization saturation (M_s) increases approx 16 percent for Fe_(65)Co_(35) and 5 percent for Fe_(90)Co_(10) alloys by milling for 8 h. Subsequent annealing of Fe_(90)Co_(10) and Fe_(65)Co_(35) powders for 105 min at 550 deg C improves the M_s about 6 and 11 percent , 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 H_c 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.