Influence of heating rates on crystallization behavior of Zr₆₅Ni₁₀Cu_17.5Al_7.5 bulk amorphous alloy

Crystallization behavior of Zr₆₅Nil₁₀ Cu_17.5Al_7.5 bulk amorphous alloy in the temperature range of glass transition to melt point was examined by DSC (differential scanning calorimeter) at different heating rates. The results reveal that there exist three stages in the whole crystallization process. Glass transition temperature, crystallization temperature and peak temperature corresponding to each stage move towards higher temperature with the increase of heating rates, which was described by Johnson-Mehl-Avrami (JMA) theory and thermal kinetics. The microstructure of the quenched bulk amorphous alloy was analyzed by XRD (X-ray diffraction). It is found that with increasing in heating temperature, phase constituent of the alloy corresponding to the three stages is evolved from quasicrystal to isomorphous system Al₂Zr₃ and NiZr₃ phase and then to isomorphous system CuZr₂ phase, cubic system NiZr₂ phase and orthothombic system Al₃Zr₂ phase. Meanwhile, crystallized product and grain size in every stage are slightly related to the heating rate, It is observed that crystallization behavior at the second stage can inhibit ones at first stage with high heating rates.