In situ fracture observation and fracture toughness analysis of Zr-based bulk amorphous alloys

The fracture property improvement of Zr-based bulk amorphous alloy containing ductile crystalline particles was explained by directly observing microfracture processes using an in situ loading stage installed inside a scanning electron microscope (SEM) chamber. Strength and apparent fracture toughness measured from the in situ fracture test of the amorphous alloy containing crystalline particles were lower than those of the monolithic amorphous alloy, whereas its ductility was higher. According to the microfracture observation, shear bands were initiated from ductile crystalline particles, and the propagation of the shear bands or cracks was blocked by crystalline particles, thereby resulting in stable crack growth which could be confirmed by the fracture resistance curve (R-curve) behavior. This increase in fracture resistance with increasing crack length improved fracture properties of the alloy containing crystalline particles, and could be explained by mechanisms of blocking of crack or shear band propagation, formation of multiple shear bands, crack blunting, and shear band branching.