We report an unusual transition from a locally ductile to a pure brittle fracture in the dynamic fracture of brittle Mg65Cu20Gd10 bulk metallic glass. The fractographic evolution from a dimple structure to a periodic corrugation pattern and then to the mirror zone along the crack propagation direction during the dynamic fracture process is discussed within the framework of the meniscus instability of the fracture process zone. This work might provide an important clue in understanding of the energy dissipation mechanism for dynamic crack propagation in brittle glassy materials.

We report the observation of nanoscale striped periodic pattern with similar distinctive characteristics independent of loading conditions on the fracture surface of various bulk metallic glasses. We demonstrate that the periodic stripes are formed by the orderly assembly of nanoscale regular dimples. The similarities between our observed striped pattern and various unequilibrium systems such as oscillating granular and colloidal suspensions systems are found. By drawing an analogy between glassy and granular materials, we propose a model that can capture and simulate the characteristics of the observed corrugations. Our results would provide insight into the origin of fracture surface roughening in brittle materials.