Investigation of shear band evolution in amorphous alloys beneath a Vickers indentation

Shear band formation has been known to be the dominant deformation mechanism at room temperature in bulk metallic glasses. However, many indentation studies have revealed only a few shear bands surrounding the indent on the top surface of the specimen. This small number of shear bands cannot account for the large plastic deformation beneath the indentations. Therefore, a bonded interface technique has been used to observe the slip-steps due to shear bands evolution. Vickers indentations were performed along the interface at increasing loads. At small indentation loads, the plastic deformation was primarily accommodated by semi-circular primary shear bands surrounding the indentation. At higher loads, secondary and tertiary shear bands were formed inside this plastic zone. A modified expanding cavity model was used to predict the plastic zone size characterized by the shear bands and to identify the stress components responsible for the evolution of various types of shear bands.