Microstructural evolution during decomposition and crystallization of the CU60Zr20Ti20 amorphous alloy

The effect of continuous heating and isothermal heat treatments on ductile Cu60Zr20Ti20 amorphous ribbons was monitored by differential scanning calorimetry, x-ray diffraction, synchrotron radiation transmission, and high-resolution transmission electron microscopy. Upon continuous heating, the alloy exhibited a glass transition, followed by a supercooled liquid region and two exothermic crystallization stages. Decomposition of the amorphous phase was also observed. The first crystallization stage resulted in the formation of a nanocomposite structure with hexagonal Cu51Zr14 particles embedded in the amorphous matrix, while in the second crystallization stage hexagonal Cu2TiZr-like phase was precipitated. The released enthalpies were 19 J/g and 30 J/g for each crystallization stage. Crystallization kinetics was studied by the classical nucleation theory. Deviations from the Johnson-Mehi-Avrami-Kolmogorov theory may be explained by the contribution of the decomposition of the amorphous matrix.