Nanocrystallization kinetics of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy

The kinetics of nanocrystallization of Finemet alloy has been investigated by differential scanning calorimetry (DSC) using various heating rates and transmission electron microscope (TEM). The changeable activation energy Ea with crystalline fraction α was given by an isoconversional method without assuming the kinetic model function, and the average value of Ea was 386 ± 30 kJ/mol. What is more important, it is shown that this process cannot be described by the JMA model and that the two-parameter empirical Sestak-Berggren equation gives a more quantitative description. The calculated value of kinetic parameters m and n in SB equation is 0.36 ± 0.04 and 1.52 ± 0.05, respectively, which means an important role of the crystallized phase on the overall kinetics and a complex kinetic process involving both nucleation and growth. And the reliability of kinetic parameters m and n is tested by comparing calculated and experimental DSC data. In addition, a detailed explanation of the nanocrystallization mechanism of Finemet alloy was given by taking account of the microstructural changes during nanocrystallization.