A Kinetic Study of the Non-isothermal Crystallization of a Zr-Based Bulk Metallic Glass

摘要

The kinetics of the non-isothermal crystallization ofZr55 Cu30Al10Ni5 bulk metallic glass was studied by differentialscanning calorimetry in the mode of continuous heating. It is found that both glass transition and crystallizationof the amorphous alloy behave in a marked kinetic nature. The activation energy E and frequency factor c0 forcrystallization were determined by the Kissinger method, which yields E = 230 kJ/mol, and k0 = 4.2 × l0Ca/s.The value of k0 is much smaller than that for conventional amorphous alloys, demonstrating that the atomicmobility in bulk metallic glasses is quite sluggish. The crystallization mechanism in the non-isothermal processwas analysed in terms of the kinetic transformation equation for the solid-state phase transformation. Thisreveals that the crystallization kinetic function f (x) for Zr55 Cu30Al10Ni5 can be described by the Johnson-Mehl-Avrami equation, i.e. f(x) = (1 - x)[- ln(1 - x)](n-1), with n = 1.75. This indicates that the non-isothermalcrystallization of Zr55 Cu30Al10Ni5 bulk metallic glass is governed by diffusion-controlled one-dimensional growth.Finally, the different crystallization mechanisms in the isothermal and non-isothermal processes are discussed.