Wavy cleavage fracture of bulk metallic glass

Dynamic instability is one of the typical cleavage fracture features in brittle materials. The authors find that dynamic instability of metallic glass starts to occur in the mirror region on the fracture surface through a wavy cracking propagation with the formation of periodic nanoscale steps. This kind of dynamic instability is associated with the early crack curving due to the intrinsic isotropic structure of metallic glass. Furthermore, they classify dynamic instabilities of cleavage fracture as crack curving at low velocity and crack branching at high velocity, corresponding to the mirror and hackle regions of metallic glass, respectively. (c) 2006 American Institute of Physics.