The evolution of heating rate on the microstructural and magnetic properties of milled nanostructured Fe1−xCox (x = 0.2, 0.3, 0.4, 0.5 and 0.7) powders

Nanostructured Fe1−xCox (x = 0.2, 0.3, 0.4, 0.5 and 0.7) powders were produced by high-energy milling and subsequent thermal annealing. The effect of heating rate on the microstructural and magnetic properties of nanostructured Fe–Co alloys was investigated. With increasing the heating rate from 2 to 45 °C/min the crystallite size decreases from 30 to 13 nm and microstrain increases from 0.03 to 0.6. The as-milled powders (35 h) and annealed alloys with 2 °C/min show the maximum and minimum values of lattice parameter, respectively. This latter may be due to the different volume fraction of grain boundaries. With decreasing the heating rate from 30 to 2 °C/min, the MS (all range of composition) improves ∼6%. The coercivity increases (up to 20 Oe) by annealing of Fe70Co30 powders with 7 °C/min. Further increase in heating rate causes the reduction in HC (to ∼8 Oe) due to the increase in crystallite size.