Nanoscale wavy fracture surface of a Pd-based bulk metallic glass

The authors report the observations of nanoscale wavy steps on fracture surface of a Pd-based bulk metallic glass. The wavy steps are generated by crack front waves. Besides this kind of steps, it is also found that there is a dispersive microscale wavy trace aligned along a backbone "branch line," which is induced by dynamic instability of a rapidly propagating crack front. Such microbranching events are evidenced as dissipating energy accumulated at the crack front by creating the additional fracture surface area when the crack propagation exceeds a critical velocity.