Effect of physical aging on Johari-Goldstein relaxation in La-based bulk metallic glass
Résumé
The influence of physical aging on the β relaxation in La60Ni15Al25 bulk metallic glass has been investigated by mechanical spectroscopy. The amplitude of the β relaxation (ΔG″) decreases while its relaxation time (τβ) increases during aging. We find that, as in organic glasses, the changes of ln (τβ) and ln (ΔGmax) are linearly correlated with ln (τβ) = b - a ln (G max ″). This behavior is discussed in term of the asymmetric double-well potential (ADWP) model, with U and Δ the energies characterizing the ADWP. It is suggested that during aging the ratio U/Δ remains approximately constant, with a value close to the coefficient describing the linear correlation between ln (τβ) and ln (G max ″)(U/Δ ∼ a). Moreover, the evolution versus aging time of ΔGmax can be described by a simple stretched exponential equation giving values of τaging consistent with tan(δ) measurements during aging. The very similar behavior of the β relaxation during aging in metallic glasses and organic material strongly suggests a common nature for this relaxation. © 2014 AIP Publishing LLC.