Effect of cobalt doping on structural and magnetic characterization of nanocrystalline Fe72−xCoxCr28 (10 < X < 22) alloys

In this study, the effect of substitution of Co with Fe on structural and magnetic characteristics of nanocrystalline Fe-Co-Cr alloys has been investigated. In this regard, different combinations of Fe, Co and Cr elements with nominal composition of Fe72−xCoxCr28 (10 < X < 22) were mechanically milled and subsequently annealed in the range of 560-640 °C. The samples were characterized using X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. Based on results, during milling process Cr and Co elements have been dissolved in Fe matrix and Fe-Cr-Co solid solution (with combination of α1 and α2 spinodal phases) has been formed. The coercivity and saturation of magnetization of formed alloys were in the range of 110-187 Oe and 150-175 emu/g, respectively. The coercivity of Fe72−xCoxCr28 (10 < X < 22) alloys showed an anomalous behavior at 18 at.% of Co as a result of optimal interaction between α1 and α2 phases in this composition. The formed Fe-Co-Cr α-phase solid solutions were not stable and transformed to σ and γ phases during annealing process at temperatures higher than 600 °C. The formation of non-magnetic σ and γ phases had destructive effect on magnetic properties of prepared samples with different composition.