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

The dynamic Young’s modulus, E, of amorphous (a-) Zr60Cu30Al10 (numbers indicate at.%) alloy was measured as a function of frequency, f, with a strain amplitude, εt, of 10−6, E(10−6,f), and also as a function of εt for f near 102 Hz, E(εt,102 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 E0 for f between 10 and 104 Hz showing local minima near 5×10, 5×102 and 5×103 Hz, which are indicative of the resonant collective motion of many atoms, where E0 is the static Young’s modulus. E(εt,102 Hz) increases showing saturation with increasing εt. Qualitatively, the outlines of E(10−6,f) and E(εt,102 Hz) observed for a-Zr60Cu30Al10 are similar to those reported for various a-alloys. Quantitatively, a change in E(εt,102 Hz) for a-Zr60Cu30Al10 is smallest among that reported for various a-alloys, presumably reflecting that the crystallization volume, (ΔV/V)x, is smallest for a-Zr60Cu30Al10. The effective charge number, Z∗, estimated from the change in E(10−6,102 Hz) due to PEC is 3.0×105, which is comparable with Z∗ reported for various a-alloys. We surmise that the number of atoms in the collective motions excited near 102 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.