On the level of mechanical loss in metallic glasses

Metallic glass samples with compositions Zr ₆₅Al _7.5Cu _27.5 and Pd ₇₇Cu ₆Si ₁₇, for which loss factors of up to 10 ^-2 have been reported, are reinvestigated with an electrostatic vibrating cantilever technique that detects dissipation factors tan δ as low as 10 ^-4. It is found that tan δ ≈ 4×10 ^-4 is a typical value for these alloys well below T _g, suggesting that previous results were limited by instrumental resolution. While aging the glasses increases their elastic moduli considerably, the measured loss factor is affected only marginally by thermal history.