Influence of Annealing Temperature on Microstructure and Magnetic Properties of FeSiNbCuBP Amorphous Alloys

Excellent soft magnetic properties of the amorphous and nanocrystalline alloys are attributed to their unique microstructure. In this work, Fe_73.5Si_13.5-xNb₃Cu₁B₉P_x (x = 0, 3.5, 7, 10 at. %) amorphous ribbons have been fabricated using the melt spinning technique. The effect of annealing temperature (475 ~ 600 ℃) on the microstructure and soft magnetic properties have been studied. According to the results, the thermal stability of FeSiNbCuBP amorphous alloys was improved by the partial substitution of Si by P. Moreover, it was found that the grain growth of α-Fe (Si) phase can be restrained by the appropriate amount of P addition and result to a grain refinement of the alloys during annealing. Base on refinement grain size (9 nm) and optimal crystallization volume fraction (47%), Fe_73.5Si₁₀Nb₃Cu₁B₉P_3.5 nanocrystalline alloy with low coercivity of 0.02 A/m and high effective permeability of 3.22 × 10⁴ was developed after annealed at 525 ℃. Besides, we propose that the migration of free electrons from P to Fe could diminish the saturation magnetization of these alloys.