Differences in surface mechanical properties of Zr-based bulk metallic glass related to stress condition

Abstract

Differences in surface mechanical properties of Zr55Cu30Al10Ni5 bulk metallic glass (BMG) was revealed through indentation tests. Inhomogeneous stress condition was constructed through fabricating asymmetrical double V-notches. Indentation responses at various locations along with and perpendicular to the connection line between the notch tips indicated a significant difference in surface hardness with range from 1.012 GPa to 1.463 GPa, corresponding to a tensile stress ranging from 11.8 MPa to 246.3 MPa. The stress gradients induced by prefabricted notches cased the anisotropy of residual indentation morphologies. Furthermore, selected area electron diffraction analysis adjacent to the notch tip exhibited typical halo ring and amorphous state, which indicated that the morphological anisotropy and differences in indentation responses were mainly caused by inhomogeneous stress and Poisson effect rather than local crystallization behaviors.