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

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 T _g, the onset temperature of crystallization T _x, and the peak temperature of crystallization T _p of the two metallic glasses were determined from DSC curves. The values of various kinetic parameters such as the activation energy of glass transition E _g, activation energy of crystallization E _p, Avrami exponent n and dimensionality of growth m were evaluated from the dependence of T _g and T _p on the heating rate. The values of E _g and E _p, 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 H _r, S, and crystallization enthalpy ΔH _c 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.