Low- and high-frequency fatigue of bulk metallic glasses

The 2.5 MeV electron-irradiation and resistance-recovery experiments were performed. It was found that the majority of atoms of a (Zr0.55Al0.10Ni0.05Cu0.30)99Y1 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 σFS (σFS 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 σFS.

Research highlights
► Recovery stages are stipulated by migration of configurations of point defects.
► Fatigue-endurance limit and the fracture mode depend on the frequency.
► Ultrasonic vibrations induce irreversible changes of the BMG structure.