The effect of temperature on the crystallization of Zr55Cu30Al10Ni5 bulk metallic glass in the glass transition region

In this paper, the effect of temperature on the isothermal crystallization of Zr55Cu30Al10Ni5 bulk metallic glass in the glass transition region was investigated by differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. It was found that the crystallization behaviour of Zr55Cu30Al10Ni5 bulk metallic glass strongly depends on the annealing temperature. The crystallization follows a diffusion-controlled growth mechanism with the formation of a dendritic-like structure in the high temperature region from 743 to 753 K. However, it follows two different mechanisms, i.e. diffusion-controlled and interface-controlled, with the formation of both dendritic-like and spherical structures, respectively, in the low temperature region from 723 to 739 K. Furthermore, the activation energy for crystallization from supercooled liquid is also temperature-dependant. The apparent activation energy is about 212 kJ/mol in the high temperature region, but 314 kJ/mol in the low temperature region. The different crystallization behaviour is believed to be due to the different structures that the metallic glass possesses at different temperatures.