Main (α) relaxation and excess wing in Zr₅₀Cu₄₀Al₁₀ bulk metallic glass investigated by mechanical spectroscopy

The dynamic mechanical relaxation behaviour of Zr₅₀Cu₄₀Al₁₀ bulk metallic glass was investigated by mechanical spectroscopy as a function of temperature. The mechanical spectra show the evidence of an "excess wing" process at the lower temperatures. The α-relaxation spectra of Zr₅₀Cu₄₀Al₁₀ bulk metallic glass was described with a Kohlrausch-Williams-Watts (KWW) function, with the exponent β_KWW = 0.5 ± 0.02. The fragility parameter m of the Zr₅₀Cu₄₀Al₁₀ is m = 57 ± 5. The values of m and β_KWW are found to agree with the correlation found for other glasses m = 250(± 30) - 320 β_KWW [R. Böhmer, K.L. Ngai, C.A. Angell et al. J. Chem. Phys. 99 (1993) 4201-4209]. Aging experiments give strong evidence that the observed "excess wing" is a submerged secondary process and not part of the α process.