Crystallization kinetics of Zr55Cu30Al10Ni5 bulk amorphous alloy

The crystallization kinetics of ZrS55Cu30Al10Ni5 bulk amorphous alloy was studied by differential scanning calorimetry in the mode of continuous heating and isothermal annealing. It is found that, in the case of continuous heating, both the glass transition temperature T-g and the crystallization peak temperature T-p display a strong dependence on the heating rate. The activation energy for glass transition and crystallization were determined by the Kissinger method, which yields E-g=894 kJ/mol and E-c=230 kJ/mol, respectively. On the other hand, the isothermal kinetics was modeled by the Johnson-Mehl-Avrami equation, the Avrami exponents were calculated to be in the range of 2.67 to 3.05. This implies that the crystallization of Zr55Cu30Al10Ni5 bulk amorphous alloy is governed by diffusion-controlled three-dimensional growth. On the basis of Arrhenius relation, the activation energy in the isothermal process was calculated to be E-c=245 kJ/mol. Finally, details of the nucleation and growth behaviors during the isothermal crystallization are discussed in terms of local Avrami exponent and local activation energy. (C) 2002 Elsevier Science B.V. All rights reserved.