Phase precipitation and isothermal crystallization kinetics of FeZrB amorphous alloy

Abstract

The crystallization process of Fe₇₈Zr₇B₁₅ (at%) amorphous ribbon was investigated by X-ray diffraction (XRD), differential scanning calorimetry and scanning electron microscopy (SEM). The fully amorphous structure of as-quenched (Aq) ribbons was confirmed by XRD pattern. The saturation magnetization (M _s) and Curie temperature of the Aq ribbon were measured as 124.3 (A·m²)/kg and 305 °C with vibrating sample magnetometer (VSM), respectively. When the ribbons was annealed at 550 °C near the first onset temperature (T _x1 = 564.9 °C), the M _s was increased by 17 %, which was caused by the formation of a dual phase structure. The isothermal crystallization kinetics and crystallization mechanism of primary α-Fe phase in the dual phase structure were studied by Arrhenius and Johnson-Mehl-Avrami-Kolmogorov equations respectively. The results showed that the crystallization of α-Fe phase was a diffusion-controlled surface nucleation growth process, and the nucleation rate decreased with longer crystallization time.

Keywords

Crystallization / Dual phase structure / Activation energy / Avrami exponent