Structural relaxation and related viscous flow of Zr–Cu–Al-based bulk glasses produced from the melts with different glass-forming ability

The relaxation ability of Zr46(Cu4/5Ag1/5)46Al8 and Zr46Cu46Al8 bulk glasses displaying different glass-forming ability (GFA) in the liquid state has been studied by measurements of the shear modulus, creep and stress relaxation. It has been found that the four-component alloy with higher GFA always displays higher relaxation ability in the glassy state. This fact does not seem to correlate with the amount of the frozen-in free volume as dependent on the GFA. It has been argued that the relaxation centers responsible for structural relaxation and related viscous flow are similar to dumbbell interstitials in simple metals. Such an approach precisely describes the kinetics of shear modulus relaxation and reasonably agrees with a phenomenological interpretation of structural relaxation-induced viscoelastic phenomena in metallic glasses.