| Crystallization of Fe_(81)B_(13.5)Si_(3.5)C₂metallic glass has been studied by differential thermal analysis, differential scanning calorimetry, X-ray diffraction and transmission electron microscopy. The crystallization temperatures are 490℃, 515℃ and 588℃ at the heating rate 5℃/min. In the first crystallization stage α-(Fe, Si) dendrites (bcc) are formed from the amorphous matrix, and in the second crystallization stave Fe₃B compounds (bct) are formed from the remaining amorphous matrix. In the last crystallization stage the metastable Fe₃B transforms into the stable Fe₂B compounds (bct), and Fe₃C compounds (orthorhombic) are formed. The exponent n in Johnson-Mehl-Avrami equation determined by Ozawa method is about 2.4 for the α-(Fe, Si) formation. This means that the nucleation rate of the α-(Fe, Si) phase is constant regardless of time. On the other hand, the exponent n for Fe₃B formation shows about 2.8, which suggests that the nucleation rate is supposed to be increased with increasing time. |
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