Fe-Co-B Soft Magnetic Ribbons: Crystallization Process, Microstructure and Coercivity.

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Fe67Co20B13 ribbons are promising soft magnetic materials.
• Controlling microstructure is key to optimizing magnetic properties.

Purpose of the Study:

• Investigate the microstructural evolution of Fe67Co20B13 ribbons during heat treatment.
• Determine the influence of heating rate, annealing time, and temperature on microstructure and coercivity.

Main Methods:

• Melt-spinning for ribbon fabrication.
• In situ transmission electron microscopy (TEM) for real-time microstructural analysis.
• Differential scanning calorimetry (DSC) for phase transition determination.
• Coercivity measurements.

Main Results:

• As-melt-spun ribbons are amorphous.
• Crystallization of α-(Fe,Co) begins near 370 °C, with a phase transition at 403 °C.
• A rapid heating rate (200 °C/min) yields finer α-(Fe,Co) crystallites compared to a slow rate (20 °C/min).
• Annealing at 485 °C for 2 s results in a homogeneous microstructure with 30 nm crystallites and coercivity of 20.5 A/m.

Conclusions:

• Heating rate is a critical parameter for controlling Fe67Co20B13 ribbon microstructure.
• Optimized annealing conditions (e.g., 485 °C for 2 s) produce a desirable microstructure for soft magnetic applications.
• Coercivity is strongly dependent on crystallite size, volume fraction, and distribution within the amorphous matrix.