Role of Mo addition on structure and magnetic properties of the Fe₈₅Si₂B₈P₄Cu₁ nanocrystalline alloy

The amorphous-forming ability (AFA), crystallization structure and magnetic properties of the melt-spun Fe_{85 − x}Si₂B₈P₄Cu₁Mo_x (x = 0–2) alloys were investigated. The addition of 1–2 at% Mo in the Fe₈₅Si₂B₈P₄Cu₁ alloy enhances the AFA with increasing the critical thickness for amorphous formation from ~ 14 to ~ 20 μm. The Mo alloying refines the microstructure and reduces the coercivity of the annealed alloys, and weakens the dependence of the coercivity on the heating rate, although it decreases the saturation magnetic flux density. After annealing under a low heating rate of 50 K/min, the average α-Fe grain size and coercivity of the Fe₈₄Si₂B₈P₄Cu₁Mo₁ alloy are ~ 25 nm and 23.9 A/m, respectively, which are lower than those of ~ 32 nm and 40.5 A/m for the base alloy. In addition, the mechanism related to the effects of Mo on the structure and magnetic properties was discussed in term of the crystallization activation energy.