Mechanism of Mechanically Induced Nanocrystallization of Amorphous FINEMET Ribbons During Milling

Melt-spun FINEMET amorphous ribbons were milled for different periods up to 65 minutes. The effect of milling time on the structure has been investigated using X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. The results showed that partial crystallization of the amorphous powder occurs during milling. Transmission electron microscope observations confirmed that an α-Fe(Si) phase with a mean crystallite size of ~9 nm nucleates inhomogenously on the plastically deformed regions. Differential scanning calorimetry analysis indicated that under high-energy vibrational milling, the Fe 23 B 6 phase becomes unstable, and Fe 2 B and Fe 3 B phases could form instead in the amorphous matrix. Gibbs free energy calculations explained the increase of crystalline phases’ nucleation rates under the high pressures resulting from the mechanical milling impacts.