Crystallization Behavior and Soft Magnetic Properties of Fe<sub>82-x</sub>Si₄B<sub>12</sub>Nb<sub>1+x</sub>Cu₁ (x=0-2) Nanocrystalline Alloys

This study investigated the effects of niobium content on the glass-forming ability, thermal stability, and magnetic properties of Fe82-xSi4B12Nb1+xCu1 (x=0-2) nanocrystalline soft magnetic alloys. X-ray diffraction showed that increasing niobium content enhanced the glass-forming ability by stabilizing the amorphous phase. Amorphous phases were observed in Nb1.5 and Nb2 ribbons, while α-Fe(Si) crystalline peaks were detected in Nb0, Nb0.5, and Nb1 ribbons. Differential scanning calorimetry demonstrated that T_X1 and T_X2, and ΔT (T_X2-T_X1) increased with higher niobium content, except for Nb2, which showed irregular behavior. Niobium improves thermal stability and widens the annealing window, but excess niobium above 3 at.% limits these effects due to secondary phase formation. Magnetic properties showed decreasing coercivity with higher niobium content. The Nb1.5 ribbon annealed at 510 °C exhibited the lowest coercivity (11.5 A/m) and high permeability (39800). These results emphasize optimizing niobium content to enhance properties in Fe-based nanocrystalline alloys.