Abstract

Herein, the effect of sub-Tg annealing on microstructure, glass transition kinetics and crystallization behavior of Ti33Zr30Cu9Ni5.5Be22.5 bulk metallic glass (BMG) is systematically studied by high-temperature differential scanning calorimetry. The results reveal that sub-Tg annealing can improve the compactness of Ti33Zr30Cu9Ni5.5Be22.5 BMG and expand the supercooled liquid region. Also, the non-isothermal crystallization behavior indicates that the glass transition activation energy (Eg) of Ti33Zr30Cu9Ni5.5Be22.5 BMG decreases and crystallization activation energy (EP1, EP2) increases after sub-Tg annealing. The changes in Eg, EP1 and EP2 exhibit sensitivity to sub-Tg annealing temperature. It is demonstrated that the isothermal crystallization time of Ti33Zr30Cu9Ni5.5Be22.5 BMG is extended by ≈1 min after 593 K annealing, indicating the inhibition of crystallization process. The Avrami indices of as-cast and sub-Tg-annealed Ti33Zr30Cu9Ni5.5Be22.5 BMGs, calculated by the Johnson-Mehl-Avrami equation, range from 2.08 to 2.30 and indicate that the three-dimensional growth process is mainly controlled by the diffusion, which is not influenced by sub-Tg annealing.

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