Crystallization kinetics of amorphous ferromagnetic Fe-B-Si alloys

By means of the real-time isothermal measurement of saturation magnetization, the double stage crystallization process of amorphous Fe sub 92.5-x B sub x Si sub 7.5 alloys with x=17.5, 15.0, and 12.5 was studied. Three kinds of characteristic times, namely, the incubation time of the second stage and the relaxation times of the first and second stages at various aging temperatures were determined by least squares fitting the experimental results to the modified JMA equation. The results showed that the second stage incubation time was almost the same as the first stage relaxation time, implying that the second stage begins after the termination of the first stage. The first and second stage relaxation times were almost the same for the specimen with x=17.5, and decreased with decreasing x. It is noteworthy that the first stage relaxation time became smaller than the second stage one for smaller x. The results are interpreted on the basis of a nucleation and growth model.