Deformation morphology underneath the Vickers indent in a Zr-based bulk metallic glass

Hardness and plastic deformation during Vickers indentation in as-cast, annealed, and fully crystallized Zr57Cu27Al11Ni5 bulk metallic glass was examined. Subsurface deformation morphology under the indenter tip was studied at various loads and for different annealing time. Appreciable plastic deformation, through shear banding, occurs in the as-cast and annealed alloys. Two different types of shear bands are observed. Their occurrence depends upon the amount of annealing and hence on the extent of crystallization. The fully crystallized alloy exhibits extensive cracking. Trends in the deformation zone size with load are consistent with the expanding cavity model, while the shear band morphology, particularly for the as-cast sample, attests the qualitative applicability of the slip line field theory.