Crystallization kinetics and soft magnetic properties of Fe₇₁Si₁₆B₉Cu₁Nb₃ amorphous alloys

Fe₇₁Si₁₆B₉Cu₁Nb₃ amorphous alloy ribbons were prepared with a single roll polar method. X-ray diffraction analysis of the surface samples was completely amorphous. The thermal stability parameters T _x, T _p, and T _end of amorphous ribbons were measured with a synchronous thermal analyzer under high purity argon gas and analyzed for their crystallization behavior. The heating rate was 10 K min⁻¹, 15 K min⁻¹, 20 K min⁻¹, and 30 K min⁻¹. The T _x and T _p of the Fe₇₁Si₁₆B₉Cu₁Nb₃ amorphous alloy increased with an increase in the heating rate, indicating that the crystallization behavior has a kinetic effect. The crystallization activation energy of the amorphous alloy was calculated using the Kissinger and Ozawa equations, respectively. The calculation results of the two methods were consistent. The sample was annealed (761 K, 786 K, 801 K, and 858 K, holding for 300 s) under the protection of high purity argon. The phase transition and microstructure transformation of the amorphous alloy during isothermal crystallization were analyzed by x-ray diffraction. When the alloy was annealed at 801 K, a single α-Fe(Si) solid solution precipitated on the amorphous matrix. Magnetic properties were measured using a vibrating sample magnetometer and observed by transmission electron microscopy. When the alloy was annealed at 786 K and 801 K, the saturation magnetic induction reached 1.22∼1.27 T, coercivity was as low as 5.3∼7.2 A m⁻¹, and the average grain size was about 10∼20 nm. (paper)