Kinetics of non-isothermal crystallization in Cu50Zr43Al7 and (Cu50Zr43Al7)95Be5 metallic glasses

Abstract

The crystallization kinetics of Cu50Zr43Al7 and (Cu50Zr43Al7)95Be5 metallic glasses was studied using differential scanning calorimetry (DSC) at four different heating rates under non-isothermal condition. The glass transition temperature Tg, the onset temperature of crystallization Tx, and the peak temperature of crystallization Tp of the two metallic glasses were determined from DSC curves. The values of various kinetic parameters such as the activation energy of glass transition Eg, activation energy of crystallization Ep, Avrami exponent n and dimensionality of growth m were evaluated from the dependence of Tg and Tp on the heating rate. The values of Eg and Ep, calculated from many different models, are found to be in good agreement with each other. The average values of the Avrami exponent n are (2.8 ± 0.4) for Cu50Zr43Al7 metallic glass and (4.2 ± 0.3) for (Cu50Zr43Al7)95Be5 metallic glass, which are consistent with the mechanism of two-dimensional growth and three-dimensional growth, respectively. Finally, the parameter Hr, S, and crystallization enthalpy ΔHc are introduced to estimate the glass-forming ability and thermal stability of metallic glasses. The result shows that the addition of Be improves the glass-forming ability and thermal stability of Cu50Zr43Al7 metallic glass.