Low- and high-frequency fatigue of bulk metallic glasses

Abstract

The 2.5 MeV electron-irradiation and resistance-recovery experiments were performed. It was found that the majority of atoms of a (Zr 0.55Al 0.10Ni 0.05Cu 0.30) 99Y 1 bulk metallic glass (BMG) possess a locally preferred order, and vacancies are stable point defects. Low- and high-frequency compression–compression fatigue experiments show that the fatigue-endurance limit and mode of the fatigue fracture of this BMG essentially depend on the cycling frequency. At the low-frequency cycling (10 Hz), the catastrophic crack is initiated mainly due to the shear-of-steps formation, and the fatigue-endurance limit is ∼0.44 σ FS ( σ FS is the fracture stress). At the high-frequency cycling (20 kHz), the catastrophic crack forms due to the propagation and mergence of nano-cracks initiated from slip layers at intercluster boundaries. The fatigue-endurance limit in this case is a random quantity with a mean value of ∼0.04 σ FS.