Anomalous elastic response of amorphous alloys suggesting collective motions of many atoms

Abstract

The dynamic Young’s modulus, E , of amorphous (a-) Zr 60 Cu 30 Al 10 (numbers indicate at.%) alloy was measured as a function of frequency, f , with a strain amplitude, ε t , of 10 −6 , E (10 −6 , f ), and also as a function of ε t for f near 10 2 Hz, E ( ε t ,10 2 Hz), by means of the vibrating reed methods. The elasticity study under the passing of electric current (PEC) was carried out too. E (10 −6 , f ) is lower than E 0 for f between 10 and 10 4 Hz showing local minima near 5×10, 5×10 2 and 5×10 3 Hz, which are indicative of the resonant collective motion of many atoms, where E 0 is the static Young’s modulus. E ( ε t ,10 2 Hz) increases showing saturation with increasing ε t . Qualitatively, the outlines of E (10 −6 , f ) and E ( ε t ,10 2 Hz) observed for a-Zr 60 Cu 30 Al 10 are similar to those reported for various a-alloys. Quantitatively, a change in E ( ε t ,10 2 Hz) for a-Zr 60 Cu 30 Al 10 is smallest among that reported for various a-alloys, presumably reflecting that the crystallization volume, (Δ V / V ) x , is smallest for a-Zr 60 Cu 30 Al 10 . The effective charge number, Z ∗ , estimated from the change in E (10 −6 ,10 2 Hz) due to PEC is 3.0×10 5 , which is comparable with Z ∗ reported for various a-alloys. We surmise that the number of atoms in the collective motions excited near 10 2 Hz is similar among various a-alloys. The E (10 −6 , f ) data suggest that the spatial sizes of the density fluctuations may show a distribution.