Effect of Sn, Bi and In on the magnetic properties and microstructure of Fe-B-C-Si-P-Cu-M nanocrystalline alloys

In this work, the effects of Sn, Bi and In microalloying elements on the magnetic properties and microstructure of Fe_83.1-x-y-zB_9.25C₃Si₃P_0.9Cu_0.75Sn_xBi_yIn_z (x, y, z = 0∼0.2) nanocrystalline alloys were investigated. It shows the microaddition of Bi and In could facilitate the formation of α-Fe nanocrystals and reduce the growth activation energy, due to their positive mixing enthalpies (ΔH_mix) with Fe and rapid diffusion of their atoms. The promoting effects of In and Bi (especially In) addition on α-Fe precipitation increased the crystallization volume fraction (v_cr) and thus enhanced the magnetic flux density (B_s) of nanocrystalline alloys. Compared with Fe_83.1B_9.25C₃Si₃P_0.9Cu_0.75 nanocrystalline alloy, the B_s of Fe₈₃B_9.25C₃Si₃P_0.9Cu_0.75Bi_0.1, Fe₈₃B_9.25C₃Si₃P_0.9Cu_0.75In_0.1, and Fe_82.9B_9.25C₃Si₃P_0.9Cu_0.75Bi_0.1In_0.1 alloys, annealed with same method, increased from 1.810 T to 1.831 T, 1.837 T and 1.849 T, respectively, together with relatively low coercivity (H_c). The present results indicate that microaddtion of low melting point element possessing positive mixing enthalpies with Fe could significantly improve the magnetic properties of the nanocrystalline alloys, which possess great potentials of application in high frequency electronic apparatus. It offered a new approach for design high performance soft magnetic nanocrysalline alloys.