Investigation of crystallization kinetics of Co-Fe-Ta-Hf-B melt-spun glassy ribbon with a high thermal stability under isochronal condition

Co-based metallic glasses have attracted the attention of many researchers due to their excellent magnetic softness, as well as their high corrosion resistance. In the present research, Co-Fe-Ta-Hf-B glassy ribbon with a high thermal stability was prepared by melt-spinning and its isochronal crystallization kinetics at different heating rates was systematically investigated. The apparent and local activation energy of crystallization, the fraction of crystals at different temperatures and other kinetics parameters were calculated according to Ozawa method. In addition, the devitrification kinetics of the produced glass was studied based on the well-known Jahnson-Mehl-Avrami (JMA) and Sestak-Berggren (SB) models. The results indicated that the local activation energy increases with progress of crystallization. Furthermore, the average activation energy calculated based on the Kissinger model was 664 kJ/mol, which is larger than many other metallic glasses, and confirms a high thermal stability of this alloy. It was shown that the JMA model cannot be used for analysis of the crystallization behavior of the present alloy and due to a complex and autocatalytic nature of crystallization, the SB model gives more liable results for investigation of crystallization kinetics.