Isochronal crystallization kinetics of Cu60Zr20Ti20 bulk metallic glass

Isochronal crystallization kinetics of Cu60Zr20Ti20 bulk metallic glass has been investigated by differential scanning calorimetry. By means of the Kissinger, Ozawa, Kempen, Matusita and Gao methods, average effective activation energies for the first and second crystallization reactions in Cu60Zr20Ti20 are calculated to be about 375 ± 9 and 312 ± 11 kJ mol−1, respectively, which are smaller than the values deduced from isothermal experiments. Meanwhile, average Avrami exponents, 3.0 ± 0.1 and 3.4 ± 0.2, for two crystallization reactions in isochronal anneals, differ from the value about 2.0 in isothermal anneals. The nonidentity of the Avrami exponents and effective activation energies may be contributed to different crystallization mechanisms and the nature of non-isokinetic between isochronal and isothermal experiments. The values of frequency factor k0 for the first and second crystallization reactions of Cu60Zr20Ti20 are (1.7 ± 0.3) × 1024 and (7.0 ± 0.8) × 1018 s−1, respectively, and the large value of k0 has been discussed in terms of the atomic configuration and interaction.

Research Highlights► Isochronal and isothermal crystallization is not isokinetic in Cu60Zr20Ti20 BMG. ► Large values of frequency factor k0 come from atomic configuration and interactions.