In situ characterization of a crack trajectory and shear bands interaction in metallic glasses

In situ SEM observations and atomic force microscopy measurements are carried out to follow changes in front of a mode I stationary crack tip initiated at the edge of thin ribbons of Cu60Zr30Ti10, Zr65Ni10Cu15Al10 and Pd42.5Cu30Ni7.5P20 metallic glasses and maintained at constant external tensile loads. While the Cu- and Zr-based metallic glasses exhibit a nano-scale shear offset in the vicinity of the crack tip, Pd-based metallic glass showed a few regularly spaced shear bands prior to fracture away from the very near crack-tip region. We have found that the discreteness, the interactions of the shear bands and crack blunting in the three metallic glasses are different. AFM frictional analyses illustrate evidence of flow defects in the vein-like structure morphology of the fractured surfaces.