New fracture morphology of amorphous Fe78Si9B13 alloy

The tensile fracture morphology of a brittle amorphous Fe-based ribbon was investigated by scanning electron microscopy(SEM). The fracture surface consists of mirror, mist and river-pattern zones with crack propagating. The formation of nanoscale damage cavity structure is a main characteristic morphology on the fracture surface. Approaching the fracture source in the mirror, these damage cavities assemble and form the nanoscale periodic striation patterns, which are neither Wallner lines nor crack front waves. At shear deformation stage, the apparent surface energy γf of amorphous Fe78Si9B13 ribbon is much smaller than that of less-brittle amorphous alloys, which indirectly indicates amorphous Fe78Si9B13 ribbon is perfectly brittle. The crack branching appears at the moment of final fracture due to the high crack propagating velocity.