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

The dynamic Young’s modulus, E, of amorphous (a-) Zr 60Cu 30Al 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 60Cu 30Al 10 are similar to those reported for various a-alloys. Quantitatively, a change in E( ε t,10 2 Hz) for a-Zr 60Cu 30Al 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 60Cu 30Al 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.