Kohlrausch exponent of amorphous Zr65Al7.5Cu27.5 determined by anelastic relaxation measurements

Abstract

Anelastic relaxations of amorphous Zr65Al7.5Cu27.5 have been studied in the range of the glass transition and in the supercooled liquid. Applying a force step function, an anelastic aftereffect of the form exp(t/τ)β (Kohlrausch–Williams–Watts function) is expected with an exponent β<1. From the measurement a value of β=0.67±0.03 is determined at Tg which confirms the empirical correlation between the fragility index m (36.4 for Zr65Al7.5Cu27.5) and β, established by Böhmer et al. This result is another indication for the metallic glass Zr65Al7.5Cu27.5 being a rather strong glass former. Furthermore, a strong increase in β just above Tg is found and is interpreted in the framework of a cluster model.