Crystallization behavior and properties characterization for high-energy state FeSiBCuC metallic glass produced by strip casting

Abstract

High-energy state Fe-based amorphous ribbons produced by twin-roll strip casting with significant thickness always suffer catastrophic coercivity (Hc) and annealing brittleness. The microstructure and property of the Fe78.9B11.8Si7.6C1Cu0.7 amorphous ribbon were investigated. After annealing with a high heating rate of 6 × 103 K/min, the saturated magnetic induction (Bs) of the twin-roll ribbon significantly improves, yet the Hc remains at an inferior level. However, compared with traditional annealing, a much lower Hc is obtained for twin-roll ribbons through multiple-rapid annealing (MRA). The improvement of soft magnetic property stems from various aspects. Due to completely released internal stress and smaller activation energy in MRA treated twin-roll ribbon, many fine α-Fe(Si) grains (20.7 nm) are precipitated on the amorphous matrix, significantly eliminating the magnetocrystalline anisotropy and neutralising the magnetostriction coefficient, reducing the Hc. On the other hand, fine α-Fe(Si) grains with volume fraction up to 80% are favorable to improve the Bs further. Besides, some shear bands appear in the fracture surfaces of MRA treated twin-roll ribbon, indicating that annealing brittleness can be restored to a certain extent. Finally, the twin-roll Fe78.9B11.8Si7.6C1Cu0.7 nanocrystalline alloy shows a high Bs of 1.72 T, low Hc of 6.2 A/m, and high hardness of 10.9 GPa by MRA treatment.