Effects of different annealing treatments on soft magnetic properties of Finemet alloy

Amorphous ribbon of Finemet alloy was obtained by rapid quenching from the melt spinning technique. Normal heat treatment and longitudinal magnetic field heat treatment methods were applied to anneal the Finemet amorphous ribbon. Microstructures of the annealed ribbons were detected by XRD. XRD results showed that nanocrystalline alpha-Fe(Si) phase formed in the amorphous matrix after both annealing treatments, resulting in the nanocrystalline / amorphous two-phase structure. Soft magnetic properties of the annealed ribbons were tested by TPS-200SA Soft Exchange Tester. It was found that soft magnetic properties were greatly improved by both annealing treatment methods, especially after the longitudinal magnetic field heat treatment, the hysteresis loop was transformed to near-rectangle shape, with the magnetic permeability mu greatly improved.